Temperature Impact on Perovskite Solar Cells Under Operation

Perovskite solar cells (PSC) have emerged as a promising substitute for conventional silicon panels, showing the fastest power conversion efficiency evolution within the photovoltaic field, going from 3.8% to 23.7% in a few years. However, PSC thermal stability is still an obstacle to their commercialization. In this study, the temperature effect on mesoporous triple-cation perovskite solar cells with two different hole extraction materials2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene (spiro-OMeTAD) and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)is assessed. The cells are exposed to thermal stress between -5 degrees C and 80 degrees C and their photovoltaic performance is monitored in situ to reproduce real operating conditions. At low temperatures, the devices present very stable values (average loss <5%), but as the temperature increases significant decreases in the open circuit potential and short-circuit current are observed. X-ray diffraction shows no change in the perovskite crystal structure with temperature. However, electron scanning microscopy and X-ray photoelectron spectroscopy indicate that temperature has a great impact on the hole extraction layer. The cell performance loss is attributed to the evaporation of additives added to the hole extraction layer to enhance its conductivity. Although the decrease in power conversion efficiency at 80 degrees C is slightly higher for PTAA cells, spiro-OMeTAD cells present a higher irreversible loss of (21.6 +/- 2.3)% after thermal stress tests, whereas PTAA devices showed only a loss of (8.2 +/- 1.6)%.