Improvement of nanopore structure SnO2 electron-transport layer for carbon-based CsPbIBr2 perovskite solar cells

Abstract

SnO2 has been widely used in perovskite solar cells (PSCs) and LEDs as a flat electron transport layer (ETL), because of its low preparation temperature and low energy consumption. However, electrons are easily captured by defects on the ETL, resulting in ion migration of perovskite, which increases the extensive hysteresis index (HI) of PSCs. By preparing surface microstructures (such as mesoporous structure and nanowire array) on the ETL, the electron transmission capacity can be improved effectively, which reduces the HI and increases photoelectric conversion efficiency (PCE).In this paper, we use a simple and high fault-tolerant method to prepare the SnO2 ETL with nanopore structure (NP–SnO2) at low temperature. The polystyrene microsphere sphere templates were prepared on flat SnO2 film by a vertical deposition method, and then SnO2 films with NP-SnO2 were prepared by template method. The size and density of nanopores in the NP-SnO2 are controlled by controlling the size of PS spheres and the concentration of PS colloidal solution. The nanopores structure could improve the quality of CsPbIBr2 crystal films. Moreover, the nanopore structure can increase the contact area between the SnO2 ETL and the CsPbIBr2 film, which provides more channels for electron transmission.The results show that CsPbIBr2 PSCs based on NP-SnO2 ETL can obtain the champion PCE, which is 6.68% (25.33% higher than the PSCs based on flat SnO2 ETL), and the HI of the PSCs based on NP-SnO2 ETL was reduced from 0.36 to 0.17.