Bottom-up holistic carrier management strategy induced synergistically by multiple chemical bonds to minimize energy losses for efficient and stable perovskite solar cells

The defects from electron transport layer, perovskite layer and their interface would result in carrier nonradiative recombination losses. Poor buried interfacial contact is detrimental to charge extraction and device stability. Here, we report a bottom-up holistic carrier management strategy induced synergistically by multiple chemical bonds to minimize bulk and interfacial energy losses for high-performance perovskite photovoltaics. 4-trifluoromethyl-benzamidine hydrochloride (TBHCl) containing –CF₃, amidine cation and Cl⁻ is in advance incorporated into SnO₂ colloid solution to realize bottom-up modification. The synergistic effect of multiple functional groups and multiple-bond-induced chemical interaction are revealed theoretically and experimentally. F and Cl⁻ can passivate oxygen vacancy and/or undercoordinated Sn⁴⁺ defects by coordinating with Sn⁴⁺. The F can suppress cation migration and modulate crystallization via hydrogen bond with FA⁺, and can passivate lead defects by coordinating with Pb²⁺. The –NH₂–CNH₂⁺ and Cl⁻ can passivate cation and anion vacancy defects through ionic bonds with perovskites, respectively. Through TBHCl modification, the suppression of agglomeration of SnO₂ nanoparticles, bulk and interfacial defect passivation, and release of tensile strains of perovskite films are demonstrated, which resulted in a PCE enhancement from 21.28% to 23.40% and improved stability. With post-treatment, the efficiency is further improved to 23.63%.