In-situ, long-term operational stability of organic photovoltaics for off-grid applications in Africa - Emmott, CJM; Moia, D; Sandwell, P; Ekins-Daukes, N; Hosel, M; Lukoschek, L; Amarasinghe, C; Krebs, FC; Nelson, J (Solar Energy Materials and Solar Cells, 2016)