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SnO 2 has gathered wide attention as an electron transport layer (ETL) in perovskite solar cells (PSCs) for its outstanding properties such as low-temperature process, high mobility, and matched energy level. However, the low-temperature annealing of SnO 2 may lead to the formation of large quantities of oxygen vacanices, which can give rise to nonradiative recombination. Herein, we introduce an alanine (C 3 H 7 NO 2) with a high fusion point to modify the quality of SnO 2 film in solution processing at a low temperature. The carboxylic acid group of alanine can crosslink to SnO 2 via a chelating interaction, leading to the decreasing in traps and increasing in carrier transmission. Furthermore, the amino group of alanine could also promote the crystallization and suppress ion migration of the perovskite film through hydrogen bonds. The result demonstrates that using the C 3 H 7 NO 2 modified SnO 2 ETL with the optimal concentration, the highest power conversion efficiency (PCE) of carbon-based CsPbIBr 2 PSC was obviously improved from 5.09% to 6.80%, leading to an increase by almost 33.60% compared to the PSC with pristine SnO 2. More importantly, the PSCs with modified SnO 2 had better long-term stability. This paper demonstrates the utility of the alanine modification approach boosting the performance of carbon-based PSCs. [ABSTRACT FROM AUTHOR]

SnO 2 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 SnO 2 ETL with nanopore structure (NP–SnO 2) at low temperature. The polystyrene microsphere sphere templates were prepared on flat SnO 2 film by a vertical deposition method, and then SnO 2 films with NP-SnO 2 were prepared by template method. The size and density of nanopores in the NP-SnO 2 are controlled by controlling the size of PS spheres and the concentration of PS colloidal solution. The nanopores structure could improve the quality of CsPbIBr 2 crystal films. Moreover, the nanopore structure can increase the contact area between the SnO 2 ETL and the CsPbIBr 2 film, which provides more channels for electron transmission. The results show that CsPbIBr 2 PSCs based on NP-SnO 2 ETL can obtain the champion PCE, which is 6.68% (25.33% higher than the PSCs based on flat SnO 2 ETL), and the HI of the PSCs based on NP-SnO 2 ETL was reduced from 0.36 to 0.17. [ABSTRACT FROM AUTHOR]