Solution processed Mo doped SnO2 as an effective ETL in the fabrication of low temperature planer perovskite solar cell under ambient conditions

Metal oxide electron transport layers play a crucial role on the extraction and transportation of charge carriers in organic-inorganic hybrid perovskite solar cells (PSCs). However, generally, fabrication of conducive metal oxide thin films requires high temperature annealing which is not compatible with roll to roll fabrication. It has been observed that a low temperature fabricated pristine metal oxide film exhibited low electrical conductivity, which has still prohibited to achieve high performance of device. Therefore, a low amount of metal doping within the pristine metal oxide films followed by low temperature thermal annealing is an effective approach to improve the electrical properties of the metal oxide thin films, and, thus, leading the higher performance of PSCs. Herein, we have developed a low temperature (180 degrees C) solution processed Molybdenum (Mo) doped SnO2 (SnO2 :Mo) as an efficient electron transport layer (ETL) for the fabrication of planer PSCs. The electrical conductivity of pristine film was significantly enhanced after the incorporation of a small amount of Mo dopant within the neat SnO2 film, which could facilitate fast transportation of photo-generated charge carriers. Moreover, due to n-type Mo doping, Fermi level of resulting film was slightly shifted upwards, which could diminish charge recombination and, hence, improved the photovoltaic performance. The power conversion efficiency (PCE) for pristine SnO2 and SnO2 :Mo based PSCs was found to be 8.47% and 10.52%, respectively, when ETL and perovskite absorber films were processed in ambient conditions with the relative humidity range of 65%-75%. Compared to pristine SnO2 , SnO2 :Mo based PSC exhibited higher performance, which was attributed to the enhanced electrical properties of the resulting doped ETL thin film. Our results indicated that low temperature (180 degrees C) solution processed SnO2 :Mo is a promising ETL for cost effective roll to roll fabrication of PSC.