Imperial College London

Dr Robert Hoye, FIMMM CEng CSci

Faculty of EngineeringDepartment of Materials

Lecturer in Materials
 
 
 
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Contact

 

+44 (0)20 7594 6048r.hoye Website

 
 
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Location

 

2.27Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

79 results found

Byranvand M, Otero-Martinez C, Ye J, Zuo W, Manna L, Saliba M, Hoye R, Polavarapu Let al., 2022, Recent Progress in Mixed A-Site Cation Halide Perovskite Thin-films and Nanocrystals for Solar Cells and Light-Emitting Diodes, Advanced Optical Materials, ISSN: 2195-1071

Journal article

Pinho B, Zhang K, Hoye R, Torrente-Murciano Let al., 2022, Importance Of Monitoring The Synthesis Of Light-Interacting Nanoparticles – A Review on In-Situ, Ex-Situ and Online Time-Resolved Studies, Advanced Optical Materials, ISSN: 2195-1071

Journal article

Andrei V, Jagt R, Rahaman M, Lari L, Lazarov V, MacManus-Driscoll J, Hoye R, Reisner Eet al., 2022, Long-term solar water and CO2 splitting with photoelectrochemical BiOI-BiVO4 tandems, Nature Materials, ISSN: 1476-1122

Photoelectrochemical (PEC) devices have been developed for direct solar fuel production, but the limited stability of submerged light absorbers hampers their commercial prospects.1,2 Here, we demonstrate photocathodes with an operational H2 evolution activity over weeks, by integrating a BiOI light absorber into a robust, oxide-based architecture with a graphite paste conductive encapsulant. In this case, the activity towards proton and CO2 reduction is mainly limited by catalyst degradation. We also introduce multiple-pixel devices as an innovative design principle for PEC systems, displaying superior photocurrents, onset biases and stability over corresponding conventional single-pixel devices. Accordingly, PEC tandem devices comprised of multiple-pixel BiOI photocathodes and BiVO4 photoanodes can sustain bias-free water splitting for 240 h, while devices with a Cu92In8 alloy catalyst demonstrate unassisted syngas production.

Journal article

Choi JW, Shin B, Gorai P, Hoye RLZ, Palgrave Ret al., 2022, Emerging earth-abundant solar absorbers, ACS Energy Letters, Vol: 7, Pages: 1553-1557, ISSN: 2380-8195

Developing solar absorbers that are efficient, low-cost, stable, and composed of nontoxic, Earth-abundant elements has long been the holy grail of next-generation photovoltaics (PV) research. (1) This effort has been disrupted by the advent and rapid rise in performance of solution-processable lead-halide perovskites. (2) One of the key enabling properties is the ability of these halide perovskites to tolerate point defects, enabling efficient PV performance despite high defect densities. (3,4) This discovery has reinvigorated efforts within the Earth-abundant PV community to design efficient solar absorbers, drawing inspiration from the halide perovskites, with particular focus on defect tolerance and achieving materials with long diffusion lengths. At the same time, the broad families of Earth-abundant solar absorbers provide valuable opportunities to overcome the toxicity and stability limitations of the lead-halide perovskites, without remaining confined solely within the perovskite family of compounds. The merging of these two communities has produced exciting new frontiers, which were explored in the recent symposium on “Earth-abundant next generation materials for solar energy” (Symposium F) at the 2021 Fall European Materials Research Society Meeting (held virtually). Herein, we feature some of the key emerging areas discussed at the Symposium: chalcogenide perovskites, II–IV–N2 compounds, antimony chalcogenides, and the computational search for novel defect-tolerant solar absorbers.

Journal article

Otero-Martinez C, Ye J, Sung J, Pastoriza-Santos I, Perez-Juste J, Xia Z, Rao A, Hoye RLZ, Polavarapu Let al., 2022, Colloidal Metal-Halide Perovskite Nanoplatelets: Thickness-Controlled Synthesis, Properties, and Application in Light-Emitting Diodes, ADVANCED MATERIALS, Vol: 34, ISSN: 0935-9648

Journal article

Hoye R, Hidalgo J, Jagt RA, Correa-Baena J-P, Fix T, MacManus-Driscoll JLet al., 2022, The role of dimensionality on the optoelectronic properties of oxide and halide perovskites, and their halide derivatives, Advanced Energy Materials, Vol: 12, ISSN: 1614-6832

Halide perovskite semiconductors have risen to prominence in photovoltaics and light-emitting diodes (LEDs), but traditional oxide perovskites, which overcome the stability limitations of their halide counterparts, have also recently witnessed a rise in potential as solar absorbers. One of the many important factors underpinning these developments is an understanding of the role of dimensionality on the optoelectronic properties and, consequently, on the performance of the materials in photovoltaics and LEDs. This review article examines the role of structural and electronic dimensionality, as well as form factor, in oxide and halide perovskites, and in lead-free alternatives to halide perovskites. Insights into how dimensionality influences the band gap, stability, charge-carrier transport, recombination processes and defect tolerance of the materials, and the impact these parameters have on device performance are brought forward. Particular emphasis is placed on carrier/exciton-phonon coupling, which plays a significant role in the materials considered, owing to their soft lattices and composition of heavy elements, and becomes more prominent as dimensionality is reduced. It is finished with a discussion of the implications on the classes of materials future efforts should focus on, as well as the key questions that need to be addressed.

Journal article

Senanayak S, Dai L, Kusch G, Shivanna R, Zhang Y, Pradhan D, Ye J, Huang Y-T, Sirringhaus H, Oliver R, Greenham N, Friend R, Hoye Ret al., 2021, Understanding the role of grain boundaries on charge-carrier and ion transport in Cs2AgBiBr6 thin films, Advanced Functional Materials, Vol: 31, Pages: 1-9, ISSN: 1616-301X

Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air, and recent demonstrations of long charge-carrier lifetimes that can exceed 1 s. In particular, Cs2AgBiBr6 has been the subject of many investigations in photovoltaic devices. However, the efficiencies of solar cells based on this double perovskite are still far from the theoretical efficiency limit of the material. Here, we investigate the role of grain size on the optoelectronic properties of Cs2AgBiBr6 thin films. We show through cathodoluminescence measurements that grain boundaries are the dominant non-radiative recombination sites. We also demonstrate through field-effect transistor and temperature-dependent transient current measurements that grain boundaries act as the main channels for ion transport. Interestingly, we find a positive correlation between carrier mobility and temperature, which resembles the hopping mechanism often seen in organic semiconductors. These findings explain the discrepancy between the long diffusion lengths >1 m found in Cs2AgBiBr6 single crystals versus the limited performance achieved in their thin film counterparts. Our work shows that mitigating the impact of grain boundaries will be critical for these double perovskite thin films to reach the performance achievable based on their intrinsic single-crystal properties.

Journal article

Rondiya SR, Jagt RA, MacManus-Driscoll JL, Walsh A, Hoye RLZet al., 2021, Self-trapping in bismuth-based semiconductors: opportunities and challenges from optoelectronic devices to quantum technologies, Applied Physics Letters, Vol: 119, ISSN: 0003-6951

Semiconductors based on bismuth halides have gained attention for a wide range of electronic applications, including photovoltaics, light-emitting diodes, and radiation detectors. Their appeal is due to their low toxicity, high environmental stability under ambient conditions, and easy processability by a wide range of scalable methods. The performance of Bi-based semiconductors is dictated by electron–phonon interactions, which limit carrier mobilities and can also influence optoelectronic performance, for example, by giving rise to a large Stokes shift for photoluminescence, unavoidable energy loss channels, or shallow optical absorption onsets. In this Perspective, we discuss the recent understanding of how polarons and self-trapped excitons/carriers form in Bi-based semiconductors (particularly for the case of Cs2AgBiBr6), their impact on the optoelectronic properties of the materials, and the consequences on device performance. Finally, we discuss the opportunities that control of electron–phonon coupling enables, including stable solid-state white lighting, and the possibilities of exploiting the strong coupling found in bipolarons for quantum technologies.

Journal article

Rondiya SR, Jadhav YA, Zivkovic A, Jathar SB, Rahane GK, Cross RW, Rokade A, Devan RS, Kolekar S, Hoye RLZ, Ghosh HN, de Leeuw NH, Jadkar SR, Dzade NYet al., 2021, Solution-processed Cd-substituted CZTS nanocrystals for sensitized liquid junction solar cells, JOURNAL OF ALLOYS AND COMPOUNDS, Vol: 890, ISSN: 0925-8388

Journal article

Huang Y-T, Kavanagh SR, Scanlon DO, Walsh A, Hoye RLZet al., 2021, Perovskite-inspired materials for photovoltaics and beyond-from design to devices (vol 32, 132004, 2021), NANOTECHNOLOGY, Vol: 32, ISSN: 0957-4484

Journal article

Pecunia V, Occhipinti L, Hoye R, 2021, Emerging indoor photovoltaic technologies for sustainable internet of things, Advanced Energy Materials, Vol: 11, Pages: 131-131, ISSN: 1614-6832

The Internet of Things (IoT) provides everyday objects and environments with “intelligence” and data connectivity to improve quality of life and the efficiency of a wide range of human activities. However, the ongoing exponential growth of the IoT device ecosystem—up to tens of billions of units to date—poses a challenge regarding how to power such devices. This Progress Report discusses how energy harvesting can address this challenge. It then discusses how indoor photovoltaics (IPV) constitutes an attractive energy harvesting solution, given its deployability, reliability, and power density. For IPV to provide an eco-friendly route to powering IoT devices, it is crucial that its underlying materials and fabrication processes are low-toxicity and not harmful to the environment over the product life cycle. A range of IPV technologies—both incumbent and emerging—developed to date is discussed, with an emphasis on their environmental sustainability. Finally, IPV based on emerging lead-free perovskite-inspired absorbers are examined, highlighting their status and prospects for low-cost, durable, and efficient energy harvesting that is not harmful to the end user and environment. By examining emerging avenues for eco-friendly IPV, timely insight is provided into promising directions toward IPV that can sustainably power the IoT revolution.

Journal article

Silva JPB, Vieira EMF, Gwozdz K, Kaim A, Goncalves LM, MacManus-Driscoll JL, Hoye RLZ, Pereira Met al., 2021, High-performance self-powered photodetectors achieved through the pyro-phototronic effect in Si/SnOx/ZnO heterojunctions, NANO ENERGY, Vol: 89, ISSN: 2211-2855

Journal article

Dey A, Ye J, De A, Debroye E, Ha SK, Bladt E, Kshirsagar AS, Wang Z, Yin J, Wang Y, Quan LN, Yan F, Gao M, Li X, Shamsi J, Debnath T, Cao M, Scheel MA, Kumar S, Steele JA, Gerhard M, Chouhan L, Xu K, Wu X-G, Li Y, Zhang Y, Dutta A, Han C, Vincon I, Rogach AL, Nag A, Samanta A, Korgel BA, Shih C-J, Gamelin DR, Son DH, Zeng H, Zhong H, Sun H, Demir HV, Scheblykin IG, Mora-Sero I, Stolarczyk JK, Zhang JZ, Feldmann J, Hofkens J, Luther JM, Perez-Prieto J, Li L, Manna L, Bodnarchuk M, Kovalenko M, Roeffaers MBJ, Pradhan N, Mohammed OF, Bakr OM, Yang P, Muller-Buschbaum P, Kamat P, Bao Q, Zhang Q, Krahne R, Galian RE, Stranks SD, Bals S, Biju V, Tisdale WA, Yan Y, Hoye RLZ, Polavarapu Let al., 2021, State of the Art and Prospects for Halide Perovskite Nanocrystals, ACS NANO, Vol: 15, Pages: 10775-10981, ISSN: 1936-0851

Journal article

Pecunia V, Zhao J, Kim C, Tuttle BR, Mei J, Li F, Peng Y, Huq TN, Hoye RLZ, Kelly ND, Dutton SE, Xia K, MacManusDriscoll JL, Sirringhaus Het al., 2021, Assessing the impact of defects on lead‐free perovskite‐inspired photovoltaics via photoinduced current transient spectroscopy, Advanced Energy Materials, Vol: 11, ISSN: 1614-6832

The formidable rise of lead‐halide perovskite photovoltaics has energized the search for lead‐free perovskite‐inspired materials (PIMs) with related optoelectronic properties but free from toxicity limitations. The photovoltaic performance of PIMs closely depends on their defect tolerance. However, a comprehensive experimental characterization of their defect‐level parameters—concentration, energy depth, and capture cross‐section—has not been pursued to date, hindering the rational development of defect‐tolerant PIMs. While mainstream, capacitance‐based techniques for defect‐level characterization have sparked controversy in lead‐halide perovskite research, their use on PIMs is also problematic due to their typical near‐intrinsic character. This study demonstrates on four representative PIMs (Cs3Sb2I9, Rb3Sb2I9, BiOI, and AgBiI4) for which Photoinduced Current Transient Spectroscopy (PICTS) offers a facile, widely applicable route to the defect‐level characterization of PIMs embedded within solar cells. Going beyond the ambiguities of the current discussion of defect tolerance, a methodology is also presented to quantitatively assess the defect tolerance of PIMs in photovoltaics based on their experimental defect‐level parameters. Finally, PICTS applied to PIM photovoltaics is revealed to be ultimately sensitive to defect‐level concentrations <1 ppb. Therefore, this study provides a versatile platform for the defect‐level characterization of PIMs and related absorbers, which can catalyze the development of green, high‐performance photovoltaics.

Journal article

Nasane MP, Rondiya SR, Jadhav CD, Rahane GR, Cross RW, Jathar S, Jadhav Y, Barma S, Nilegave D, Jadkar V, Rokade A, Funde A, Chavan PG, Hoye RLZ, Dzade NY, Jadkar Set al., 2021, An interlinked computational-experimental investigation into SnS nanoflakes for field emission applications, New Journal of Chemistry: a journal for new directions in chemistry, Vol: 45, Pages: 11768-11779, ISSN: 1144-0546

Layered binary semiconductor materials have attracted significant interest as field emitters due to their low work function, mechanical stability, and high thermal, and electrical conductivity. Herein, we report a systematic experimental and theoretical investigation of SnS nanoflakes synthesized using a simple, low-cost, and non-toxic hot injection method for field emission studies. The field emission studies were carried out on SnS nanoflake thin films prepared using a simple spin coating technique. The X-ray diffraction (XRD) and Raman spectroscopy analysis revealed an orthorhombic phase of SnS. Scanning electron microscopy (SEM) analysis revealed that as-synthesized SnS has a flakes like morphology. The formation of pure-phase SnS nanoflakes was further confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The UV-Visible-NIR spectroscopy analysis shows that SnS nanoflakes have a sharp absorption edge observed in the UV region and have a band gap of ∼1.66 eV. In addition, the first-principles density functional theory (DFT) calculations were carried out to provide atomic-level insights into the crystal structure, band structure, and density of states (DOS) of SnS nanoflakes. The field emission properties of SnS nanoflakes were also investigated and it was found that SnS nanoflakes have a low turn-on field (∼6.2 V μm−1 for 10 μA cm−2), high emission current density (∼104 μA cm−2 at 8.0 V μm−1), superior current stability (∼1 μA for ∼2.5 hrs), and a high field enhancement factor of 1735. First principles calculations predicted lower work function for different surfaces, especially for the most stable SnS (001) surface (ϕ = 4.32 eV), which is believed to be responsible for the observed facile electron emission characteristics. We anticipate that the SnS could be utilized for future vacuum nano/microelectronic and flat panel display applications due to the low turn-on field and flakes like structure.

Journal article

Perini C, Doherty T, Stranks S, Correa-Baena J-P, Hoye Ret al., 2021, Pressing challenges in halide perovskite photovoltaics - from the atomic to module level, Joule, Vol: 5, Pages: 1024-1030, ISSN: 2542-4351

Journal article

Napari M, Huq TN, Hoye RLZ, MacManusDriscoll JLet al., 2021, Nickel oxide thin films grown by chemical deposition techniques: Potential and challenges in next‐generation rigid and flexible device applications, InfoMat, Vol: 3, Pages: 536-576, ISSN: 2567-3165

Journal article

Polavarapu L, Ye J, Byranvand MM, Martínez CO, Hoye RL, Saliba Met al., 2021, Defect passivation in lead-halide perovskite nanocrystals and thin films: toward efficient LEDs and solar cells., Angewandte Chemie International Edition, ISSN: 1433-7851

Lead-halide perovskites (LHPs), in the form of both colloidal nanocrystals (NCs) and thin films, have emerged over the past decade as leading candidates for next-generation, efficient light-emitting diodes (LEDs) and solar cells. Owing to their high photoluminescence quantum yields (PLQYs), LHPs efficiently convert injected charge-carriers to light and vice versa . However, despite the defect-tolerance of LHPs, defects at the surface of colloidal NCs and at grain boundaries in thin films play a critical role in charge-carrier transport and non-radiative recombination, which lowers PLQYs, device efficiency and stability. Therefore, understanding the defects that play a key role in limiting performance, and developing effective passivation routes is critical for achieving advances in performance, and therefore features at the forefront of perovskite research. This review presents the current understanding of the defects in perovskites (both colloidal NCs and thin films) and their influence on the optical and charge-carrier transport properties. The review also discusses the passivation strategies toward improving the efficiencies of perovskite-based LEDs and solar cells.

Journal article

Gan J, Yu M, Hoye RLZ, Musselman KP, Li Y, Liu X, Zheng Y, Zu X, Li S, MacManus-Driscoll JL, Qiao Let al., 2021, Defects, photophysics and passivation in Pb-based colloidal quantum dot photovoltaics, Materials Today Nano, Vol: 13, Pages: 1-17, ISSN: 2588-8420

Colloidal quantum dots (CQDs) are a class of third-generation materials for photovoltaics (PVs) that are promising for enabling high efficiency devices with potential for exceeding the Shockley-Queisser limit. This is due to their potential to decrease thermal dissipation via multiple exciton generation during charge conversion and collection, which could potentially lead to an increase in the photovoltage or photocurrent in colloidal quantum dot photovoltaics (CQD PVs). But despite a predicted upper efficiency limit of 42%–44%, the highest power conversion efficiencies of these PVs using lead sulfide colloidal quantum dots (PbS CQDs) remains at approximately 13% on a laboratory scale. For further improvements, the fundamental recombination mechanisms need to be studied to determine their effects on the open-circuit voltage (VOC) and charge-carrier lifetime as well as the diffusion length of the carriers. Also, surface defect passivation and interface engineering should be studied. In this work, we discuss different pathways for non-radiative recombination losses in lead sulfide colloidal quantum dot photovoltaics (PbS CQD PVs), as well as the strategies for reducing these losses by the passivation of the surface and interface defects. We also discuss routes to overcome limits in the diffusion length of the carriers through the engineering of charge transport layers. This work provides routes for the fabrication of highly efficient CQD PVs.

Journal article

Napari M, Huq TN, Meeth DJ, Heikkilä MJ, Niang KM, Wang H, Iivonen T, Wang H, Leskelä M, Ritala M, Flewitt AJ, Hoye R, MacManus-Driscoll JLet al., 2021, Role of ALD Al2O3 surface passivation on the performance of p-type Cu2O thin film transistors, ACS Applied Materials and Interfaces, Vol: 13, Pages: 4156-4164, ISSN: 1944-8244

High-performance p-type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu2O semiconductor channel grown by atomic layer deposition (ALD). The TFT switching characteristics were improved by applying a thin ALD Al2O3 passivation layer on the Cu2O channel, followed by vacuum annealing at 300 °C. Detailed characterization by transmission electron microscopy–energy dispersive X-ray analysis and X-ray photoelectron spectroscopy shows that the surface of Cu2O is reduced following Al2O3 deposition and indicates the formation of a 1–2 nm thick CuAlO2 interfacial layer. This, together with field-effect passivation caused by the high negative fixed charge of the ALD Al2O3, leads to an improvement in the TFT performance by reducing the density of deep trap states as well as by reducing the accumulation of electrons in the semiconducting layer in the device off-state.

Journal article

Huang Y-T, Kavanagh S, Scanlon D, Walsh A, Hoye Ret al., 2021, Perovskite-inspired materials for photovoltaics and beyond – from design to devices, Nanotechnology, Vol: 32, Pages: 1-60, ISSN: 0957-4484

NanotechnologyACCEPTED MANUSCRIPT • The following article is Open accessPerovskite-Inspired Materials for Photovoltaics and Beyond – From Design to DevicesYi-Teng Huang1, Seán R. Kavanagh2, David O Scanlon3, Aron Walsh4 and Robert Hoye5Accepted Manuscript online 1 December 2020 • © 2020 The Author(s). Published by IOP Publishing Ltd.What is an Accepted Manuscript?Download Accepted Manuscript PDFDownload PDFArticle has an altmetric score of 6Turn on MathJaxShare this article Share this content via email Share on Facebook Share on Twitter Share on Google+ Share on MendeleyArticle informationAbstractLead-halide perovskites have demonstrated astonishing increases in power conversion efficiency in photovoltaics over the last decade. The most efficient perovskite devices now outperform industry-standard multi-crystalline silicon solar cells, despite the fact that perovskites are typically grown at low temperature using simple solution-based methods. However, the toxicity of lead and its ready solubility in water are concerns for widespread implementation. These challenges, alongside the many successes of the perovskites, have motivated significant efforts across multiple disciplines to find lead-free and stable alternatives which could mimic the ability of the perovskites to achieve high performance with low temperature, facile fabrication methods. This Review discusses the computational and experimental approaches that have been taken to discover lead-free perovskite-inspired materials, and the recent successes and challenges in synthesizing these compounds. The atomistic origins of the extraordinary performance exhibited by lead-halide perovskites in photovoltaic devices is discussed, alongside the key challenges in engineering such high-performance in alternative, next-generation materials. Beyond photovoltaics, this Review discusses the impact perovskite-inspired materials have had in spurring efforts to apply new materials i

Journal article

Li Z, Kavanagh S, Napari M, Palgrave RG, Abdi-Jalebi M, Andaji-Garmaroudi Z, Davies DW, Laitinen M, Julin J, Isaacs MA, Friend RH, Scanlon DO, Walsh A, Hoye Ret al., 2020, Bandgap lowering in mixed alloys ofCs2Ag(SbxBi1-x)Br6 double perovskite thin films, Journal of Materials Chemistry A, Vol: 8, Pages: 21780-21788, ISSN: 2050-7488

Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air and long charge-carrier lifetimes. However, most double perovskites, including Cs2AgBiBr6, have wide bandgaps, which limits photoconversion efficiencies. The bandgap can be reduced through alloying with Sb3+, but Sb-rich alloys are difficult to synthesize due to the high formation energy of Cs2AgSbBr6, which itself has a wide bandgap. We develop a solution-based route to synthesize phase-pure Cs2Ag(SbxBi1−x)Br6 thin films, with the mixing parameter x continuously varying over the entire composition range. We reveal that the mixed alloys (x between 0.5 and 0.9) demonstrate smaller bandgaps than the pure Sb- and Bi-based compounds. The reduction in the bandgap of Cs2AgBiBr6 achieved through alloying (170 meV) is larger than if the mixed alloys had obeyed Vegard's law (70 meV). Through in-depth computations, we propose that bandgap lowering arises from the type II band alignment between Cs2AgBiBr6 and Cs2AgSbBr6. The energy mismatch between the Bi and Sb s and p atomic orbitals, coupled with their non-linear mixing, results in the alloys adopting a smaller bandgap than the pure compounds. Our work demonstrates an approach to achieve bandgap reduction and highlights that bandgap bowing may be found in other double perovskite alloys by pairing together materials forming a type II band alignment.

Journal article

Peng Y, Huq T, Mei J, Portilla L, Jagt RA, Occhipinti L, MacManus-Driscoll JL, Hoye R, Pecunia Vet al., 2020, Lead-free perovskite-inspired absorbers for indoor photovoltaics, Advanced Energy Materials, Vol: 11, Pages: 1-12, ISSN: 1614-6832

With the exponential rise in the market value and number of devices part of the Internet of Things (IoT), the demand for indoor photovoltaics (IPV) to power autonomous devices is predicted to rapidly increase. Lead‐free perovskite‐inspired materials (PIMs) have recently attracted significant attention in photovoltaics research, due to the similarity of their electronic structure to high‐performance lead‐halide perovskites, but without the same toxicity limitations. However, the capability of PIMs for indoor light harvesting has not yet been considered. Herein, two exemplar PIMs, BiOI and Cs3Sb2ClxI9‐x are examined. It is shown that while their bandgaps are too wide for single‐junction solar cells, they are close to the optimum for indoor light harvesting. As a result, while BiOI and Cs3Sb2ClxI9‐x devices are only circa 1%‐efficient under 1‐sun illumination, their efficiencies increase to 4–5% under indoor illumination. These efficiencies are within the range of reported values for hydrogenated amorphous silicon, i.e., the industry standard for IPV. It is demonstrated that such performance levels are already sufficient for millimeter‐scale PIM devices to power thin‐film‐transistor circuits. Intensity‐dependent and optical loss analyses show that future improvements in efficiency are possible. Furthermore, calculations of the optically limited efficiency of these and other low‐toxicity PIMs reveal their considerable potential for IPV, thus encouraging future efforts for their exploration for powering IoT devices.

Journal article

Raninga RD, Jagt RA, Béchu S, Huq TN, Li W, Nikolka M, Lin Y-H, Sun M, Li Z, Li W, Bouttemy M, Frégnaux M, Snaith HJ, Schulz P, MacManus-Driscoll JL, Hoye RLZet al., 2020, Strong performance enhancement in lead-halide perovskite solar cells through rapid, atmospheric deposition of n-type buffer layer oxides, Nano Energy, Vol: 75, Pages: 104946-104946, ISSN: 2211-2855

Journal article

Jagt RA, Huq TN, Hill SA, Thway M, Liu T, Napari M, Roose B, Gałkowski K, Li W, Lin SF, Stranks SD, MacManus-Driscoll JL, Hoye RLZet al., 2020, Rapid vapor-phase deposition of high-mobility p-Type buffer layers on perovskite photovoltaics for efficient semi-transparent devices, ACS Energy Letters, Vol: 5, Pages: 2456-2465, ISSN: 2380-8195

Perovskite solar cells (PSCs) with transparent electrodes can be integrated with existing solar panels in tandem configurations to increase the power conversion efficiency. A critical layer in semi-transparent PSCs is the inorganic buffer layer, which protects the PSC against damage when the transparent electrode is sputtered on top. The development of n-i-p structured semi-transparent PSCs has been hampered by the lack of suitable p-type buffer layers. In this work we develop a p-type CuOx buffer layer, which can be grown uniformly over the perovskite device without damaging the perovskite or organic hole transport layers. The CuOx layer has high hole mobility (4.3 ± 2 cm2 V-1 s-1), high transmittance (>95%), and a suitable ionization potential for hole extraction (5.3 ± 0.2 eV). Semi-transparent PSCs with efficiencies up to 16.7% are achieved using the CuOx buffer layer. Our work demonstrates a new approach to integrate n-i-p structured PSCs into tandem configurations, as well as enable the development of other devices that need high quality, protective p-type layers.

Journal article

Hoye R, Fakharuddin A, Congreve D, Wang J, Schmidt-Mende Let al., 2020, Light emission from perovskite materials, APL Materials, Vol: 8, Pages: 070401-1-070401-3, ISSN: 2166-532X

Journal article

Napari M, Huq TN, Maity T, Gomersall D, Niang KM, Barthel A, Thompson JE, Kinnunen S, Arstila K, Sajavaara T, Hoye RLZ, Flewitt AJ, MacManusDriscoll JLet al., 2020, Antiferromagnetism and p‐type conductivity of nonstoichiometric nickel oxide thin films, Infomat, Vol: 2, Pages: 769-774, ISSN: 2567-3165

Plasma‐enhanced atomic layer deposition was used to grow non‐stoichiometric nickel oxide thin films with low impurity content, high crystalline quality, and p‐type conductivity. Despite the non‐stoichiometry, the films retained the antiferromagnetic property of NiO.

Journal article

Jagt RA, Huq TN, Börsig KM, Sauven D, Lee LC, MacManus-Driscoll JL, Hoye RLZet al., 2020, Controlling the preferred orientation of layered BiOI solar absorbers, Journal of Materials Chemistry C, Vol: 15 jun 2020, Pages: 10791-10797, ISSN: 2050-7526

Bismuth oxyiodide (BiOI) has gained attention for photovoltaics, photocatalysis and photodetectors owing to its composition of non-toxic elements, tolerance to point defects, and highly-suitable optical properties. But like many other bismuth-based compounds, BiOI is a layered material with anisotropic transport properties, making control over the preferred orientation critical for achieving optimal device performance. In this work, we develop new insights into the growth mechanism of BiOI synthesized by chemical vapor deposition (CVD) and show how the preferred orientation can be controlled. By adjusting the precursor and substrate temperatures to tune whether or not we are in a nucleation- or growth-controlled regime, we reproducibly vary the ratio of the (001) and (110) orientations by over two orders of magnitude. As a result, we achieve highly c-axis oriented films, which leads to less shunting than a/b-axis oriented films, resulting in improved open-circuit voltages from a median value of 0.7 V (a/b-axis oriented) to 0.9 V (c-axis oriented) in BiOI solar cells. More broadly, the described mechanisms can be used to control the preferred orientation in other low-dimensional materials, which will be important for achieving improved performance across a wide variety of devices.

Journal article

Gan J, Hoye R, Ievskaya Y, Vines L, Marin A, MacManus-Driscoll J, Monakhov Eet al., 2020, Elucidating the origin of external quantum efficiency losses in cuprous oxide solar cells through defect analysis, Solar Energy Materials and Solar Cells, Vol: 209, Pages: 1-8, ISSN: 0165-1633

Heterojunction Cu2O solar cells are an important class of earth-abundant photovoltaics that can be synthesized by a variety of techniques, including electrochemical deposition (ECD) and thermal oxidation (TO). The latter gives the most efficient solar cells of up to 8.1 %, but is limited by low external quantum efficiencies (EQE) in the long wavelength region. By contrast, ECD Cu2O gives higher short wavelength EQEs of up to 90 %. We elucidate the cause of this difference by characterizing and comparing ECD and TO films using impedance spectroscopy and fitting with a lumped circuit model to determine the trap density, followed by simulations. The data indicates that TO Cu2O has a higher density of interface defects, located approximately 0.5 eV above the valence band maximum (NV),and lower bulk defect density thus explaining the lower short wavelength EQEs and higher long wavelength EQEs. This work shows that a route to further efficiency increases of TO Cu2O is to reduce the density of interface defect states.

Journal article

Peng Y, Li F, Wang Y, Li Y, Hoye RLZ, Feng L, Xia K, Pecunia Vet al., 2020, Enhanced photoconversion efficiency in cesium-antimony-halide perovskite derivatives by tuning crystallographic dimensionality, Applied Materials Today, Vol: 19, Pages: 1-11, ISSN: 2352-9407

Lead-based perovskites have reached prominence in optoelectronic and photovoltaic research, yet their toxicity has prompted the search for alternative lead-free compounds. All-inorganic antimony-/bismuth-halide perovskite derivatives have been identified as a promising class of materials. Despite attractive bulk optoelectronic properties, their optoelectronic device performance has been lagging behind. Here we examine one of their most promising embodiments, the all-inorganic cesium-antimony-halide system. Through solution-based halide mixing, we achieve its structural conversion from a zero-dimensional to a layered phase at processing temperatures <150 °C, i.e., much lower than those relied upon in the prior literature (≥230 °C) of all-inorganic cesium-antimony halides. In order to evaluate the technological significance of this finding, we integrate our layered films into a sandwich-type device structure, and characterize their external quantum efficiency and photovoltaic behavior. We find that the structural conversion leads to a considerable enhancement in the optoelectronic device performance. Additionally, photocurrent-power characterization and Hall effect measurements reveal that this performance enhancement is brought about by an improvement in charge carrier transport, which can be exploited due to the unoriented nature of our low-temperature-processed layered films. Such performance boost and mechanistic insight constitute an important step in realizing the full potential of these (and related) compounds for their application in lead-free optoelectronic and photovoltaic devices, e.g., for top-cell in tandem photovoltaics, indoor photovoltaics, and photodetectors.

Journal article

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