We investigate the use of simple nontoxic Cu 2 SnS 3 (CTS) nanoparticles (NPs) as low-cost dopant-free hole-transport materials (HTMs) a substitute for spiro-OMeTAD in an n-ip mesoscopic architecture of perovskite solar cells (PSCs). Besides, this work confirms the critical role of the crystalline phase of CTS NPs on the performance of the device. Using a facile one-pot heating-up procedure, pure zincblende and wurtzite structures of CTS NPs were obtained by sulfur element and thiourea as the sulfur source, respectively, and were dispersed in chloroform to make very stable nonpolar ink that is compatible with the perovskite. Nanoparticles with the wurtzite crystal phase showed much better photovoltaic performance compared to the zincblende phase with efficiencies of 13.01 and 7.87%, respectively. The efficiency of the reference solar cell using spiro-OMeTAD was 16.01%. Results from impedance spectroscopy and external quantum efficiency show that by switching from wurtzite-CTS to zincblende-CTS, the resistance of charge transfer at the perovskite/HTM interface is increased, which matches with the descending trend of fill factor of the corresponding cells. According to the morphological characteristics and electrical properties of HTM layers, the better performance of wurtzite-CTS in comparison with zincblende-CTS is due to two factors: (i) enhancement of the band-gap energy and alignment of the valance band maximum; and (ii) uniform smooth coverage of the perovskite film by monodispersed wurtzite-CTS NPs.

Antisolvent crystallization is known as an effective approach for the deposition of pinhole-free solution-processed perovskite layers for high-performance solar cells. Here, we introduce a modified antisolvent dripping method by adding tetra ethyl orthosilicate (TEOS) into chlorobenzene as a conventional antisolvent. Through TEOS modification, perovskite solar cells show efficiencies as high as 16% with more than 85% retention after 290 h storage at ambient conditions in comparison to 20% in pristine cells. This significant enhancement in efficiency and stability mainly related to the decrement of the density of surface defects, which is confirmed by considerably enhanced photoluminescence of perovskite layers. Also, electrochemical impedance spectroscopy results show lower charge recombination at interfaces in modified cells. Regarding the obtained results, our modified antisolvent approach is a simple and promising route to prepare high-quality perovskite layers for solar cell applications.