Large area, high efficiency and stable perovskite solar cells enabled by fine control of intermediate phase

Organic-inorganic lead halide perovskites have shown great potential in efficient photovoltaic devices. However, there are issues related to device stability and reliability and the high power conversion efficiencies (PCE) are typically demonstrated on cell areas much less than 0.2 cm². The main challenges which limit high efficiencies in larger area devices lie on the low temperature solution processing methods which typically produce lower quality perovskites with defects (pinholes and traps) and the undesired increase in series resistance with cell area. Herein, the control of the dimethyl sulfoxide (DMSO) adduct intermediate phase for the formation of the defect-free perovskite layer and their suitability for larger area solar cells are investigated. We have also selected different conducting substrates, namely indium tin oxide (ITO) with sheet resistance of 10 Ω/□ and fluorine doped tin oxide (FTO) substrates with sheet resistances of 7 and 15 Ω/□ to characterize the effect of substrate sheet resistance and transparency on the photovoltaic performance in large area devices. We demonstrate high PCEs of 18.2% for small area devices (0.16 cm²) and 15.1% for large area device (2 cm²) using the DMSO-enriched recipe. In addition, enhanced device stability was observed, where the devices sustained 94% of their initial efficiency after 105 days without encapsulation. These results confirm that the fine control of adduct intermediate phase for reduced-defect perovskite film provides a simple and universal solution for larger area, efficient and stable perovskite solar cells.