Multifunctional Polymer Restraint of the Agglomeration of SnO 2 Nanocrystals for Efficient and Stable Planar Perovskite Solar Cells.

The aggregation of SnO 2 nanocrystals due to van der Waals interactions is not conducive to the realization of a compact and pinhole-free electron transport layer (ETL). Herein, we have utilized potassium alginate (PA) to self-assemble SnO 2 nanocrystals, forming a PA-SnO 2 ETL for perovskite solar cells (PSCs). Through density functional theory (DFT) calculations, PA can be effectively absorbed onto the surface of SnO 2 . This inhibits the agglomeration of SnO 2 nanocrystals in solution, forming a smoother pinhole-free film. This also changes the surface contact potential (CPD) of the SnO 2 film, which leads to a reduction in the energy barrier between the ETL and the perovskite layers, promotes effective charge transfer, and reduces trap density. Consequently, the power conversion efficiency (PCE) of PSCs with a PA-SnO 2 ETL increased from 19.24% to 22.16%, and the short-circuit current ( J SC ) was enhanced from 23.52 to 25.21 mA cm -2 . Furthermore, the PA-modified unpackaged device demonstrates better humidity stability compared to the original device.