Halide perovskite crystals and thin-films for optoelectronic applications

Professor William Jo

Department of Physics, Ewha Womans University, Seoul 03760, Korea 

Reported perovskite devices based on polycrystalline thin films suffer immensely from poor stability and high trap density owing to grain boundaries limiting their performance. Perovskite single crystal structures have been recently explored to construct stable devices and reduce the trap density compared to their thin-film counterpart. We present a novel method of growing sizable CH3NH3PbX3 (X = I, Br, and Cl) single crystals based on the high solubility characteristic of hybrid perovskites at low temperature within inverse temperature crystallization. Photogenerated charge transport is critical to further improving the performance of perovskite-based optical devices. In this study, characteristics of photodetectors has been studied with a variety of electrodes including Au, Ag, and TiO2. The transport mechanism of the photogenerated carriers in each device is elucidated by analysis of the current density-voltage curves obtained under dark or illuminated conditions at a visible wavelength of 640 nm or a near-ultraviolet wavelength of 405 nm. The photocurrent under the super-bandgap illumination is improved under the hole-device of p-type iodide and bromide crystals and the electron-device of n-type chloride crystals. The defect-assisted excitation under sub-bandgap illumination is associated with generation of the holes with the defects located near the conduction band or the electrons with the valence band in each perovskite materials. Furthermore, the photodetection responsivity exhibits strong enhancement of about 10 times or more by selection of the proper electrode. The present results suggest a promising strategy for designing efficient photodetectors using photogenerated electrons or holes and trap-assisted photocarriers that contribute to photocurrent enhancement.

References

[1] J. H. Kim, J. Park, Y.-H. Kim, and W. Jo, “Improvement of Open-Circuit Voltage Deficit via Pre-treated NH4+ Ion Modification of Interface between SnO2 and Perovskite Solar Cells”, Small, 2204173 (2022).

[2] H. R. Jung, Y. Cho, and W. Jo, “UV and visible photodetectors of MAPbBr3 and MAPbCl3 perovskite single crystals via single photocarrier transport design”, Advanced Optical Materials, 10, 2102175 (2022).