Synergy Effect of a π‐Conjugated Ionic Compound: Dual Interfacial Energy Level Regulation and Passivation to Promote V_oc and Stability of Planar Perovskite Solar Cells

Abstract

Defects and energy offsets at the bulk and heterojunction interfaces of perovskite are detrimental to the efficiency and stability of perovskite solar cells (PSCs). Herein, we designed an amphiphilic π‐conjugated ionic compound (QAPyBF4), implementing simultaneous defects passivation and interface energy level alignments. The p‐type conjugated cations passivated the surface trap states and optimized energy alignment at the perovskite/hole transport layer. The highly electronegative [BF4]− enriched at the SnO2 interface featured desired band alignment due to the dipole moment of this interlayer. The planar n‐i‐p PSC had an efficiency of 23.1 % with Voc of 1.2 V. Notably, the synergy effect elevated the intrinsic endothermic decomposition temperature of the perovskite. The modified devices showed excellent long‐term thermal (85 °C) and operational stability at the maximum power point for 1000 h at 45 °C under continuous one‐sun illumination with no appreciable efficiency loss.

Rationally designed universal passivator for high-performance single-junction and tandem perovskite solar cells

“…[25][26] At this interface, there are usually various defects simultaneously encompassing positively charged defects (e.g., undercoordinated Pb 2+ and halide vacancies) and negatively charged defects (such as cation vacancies and PbI 3 -). 27 To effectively heal these harmful defects, a variety of interface materials have been developed, mainly involving low-dimensional perovskites, [28][29][30] Lewis bases [31][32][33] , organic cations, 34 and organic salts 8, 25,[35][36][37] . Compared with other interface materials, organic salts exhibit great potential in minimizing nonradiative recombination and suppressing ion migration due to their ability to simultaneously passivate positively and negatively charged defects.…”