Highly Enhanced Efficiency of Planar Perovskite Solar Cells by an Electron Transport Layer Using Phytic Acid-Complexed SnO2 Colloids

SnO2 aqueous colloids as electron transport layers (ETLs) have been widely employed in planar perovskite solar cells (PSCs). However, the surface defects and energy level mismatch at the SnO2 ETL/perovskite interface are still great challenges for the power conversion efficiency (PCE) improvement. Herein, a natural and nontoxic phytic acid (PA) compound is introduced into the SnO2 aqueous colloids to prepare the ETL to depress its defects, and systematically study the influence of different PA complexation on the photovoltaic performance of PSCs. The results demonstrate that PA complexation can assemble unique coordination complexes between PA and SnO2 nanocrystals (NCs) in a new bonding of Sn-O-P, which can passivate SnO2 inherent surface defects and tune the electronic properties of SnO2 ETLs. PA complexation can significantly disaggregate the SnO2 oligomers and reduce the cluster size distribution from 98.37 to 15.87 nm. Meanwhile, the reduction of surface trap states inhibits the potential barriers, thus the electrical conductivity is about two times as high as compared with the pristine SnO2 ETLs. Consequently, a high PCE of 21.43% in PA-SnO2-based PSCs is obtained, which presents an improvement of 10.9% over that of the pristine SnO2-based PSCs.

Automated summary

Introducing phytic acid (PA) compound into SnO2 aqueous colloids for electron transport layer (ETL) preparation can reduce defects and improve photovoltaic performance of planar perovskite solar cells (PSCs). The unique coordination complexes formed between PA and SnO2 nanocrystals (NCs) passivate surface defects and enhance electrical conductivity, leading to a significant increase in power conversion efficiency (PCE).