Choline Derivative as a Multifunctional Interfacial Bridge through Synergistic Effects for Improving the Efficiency and Stability of Perovskite Solar Cells

The interfacial carrier non-radiative recombination caused by buried defects in electron transport layer (ETL) material and the energy barrier severely hinders further improvement in efficiency and stability of perovskite solar cells (PSCs). In this study, the effect of the SnO2 ETL doped with choline chloride (CC), acetylcholine chloride (AC), and phosphocholine chloride sodium salt (PCSS) are investigated. These dopants modify the interface between SnO2 ETL and perovskite layer, acting as a bridge through synergistic effects to form uniform ETL films, enhance the interface contact, and passivate defects. Ultimately, compared with CC (which with OH) and AC (which with C=O), the PCSS with P = O and sodium ions groups is more beneficial for improving performance. The device based on PCSS-doped SnO2 ETL achieves an efficiency of 23.06% with a high V-OC of 1.2 V, which is considerably higher than the control device (20.55%). Moreover, after aging for 500 h at a temperature of 25 C-degrees and relative humidity (RH) of 30-40%, the unsealed device based on SnO2-PCSS ETL maintains 94% of its initial efficiency, while the control device only 80%. This study provides a meaningful reference for the design and selection of ideal pre-buried additive molecules.