A comprehensive optimization strategy: potassium phytate-doped SnO2 as the electron-transport layer for high-efficiency perovskite solar cells

Abstract

For perovskite solar cells (PSCs), the electron transport layer (ETL) is a key component for the separation and transport of charge carriers. Also, the modulation of perovskite crystallization processes is important to obtain highly crystalline and stable perovskite films. Herein, we proposed a novel strategy, i.e. potassium phytate (PP)-doped SnO₂ as the ETL. The incorporation of PP into the SnO₂ ETL not only adjusts the electronic properties of SnO₂ but also optimizes the energy level arrangement between SnO₂ and the perovskite by passivating the Sn dangling bonds within SnO₂. As a result, a better transport/extraction of electrons across the ETL and the ETL/perovskite interface is achieved. Meanwhile, the diffusible K⁺ cations from the hydrolytic PP fill the lattice defect sites in the perovskite and improve dramatically the crystallinity of the perovskite, and hence reduce the charge trap density of the perovskite and suppress the charge recombination loss. The power conversion efficiency (PCE) is enhanced from 20.14% to 22.14% for the champion PP–SnO₂ PSCs relative to the pristine devices. In addition, the stability against humidity of the unencapsulated PSCs with the PP–SnO₂ ETL is improved obviously compared to the pristine devices. This work provides a comprehensive optimization strategy for high efficiency and stability PSCs.