A conjugated ligand interfacial modifier for enhancing efficiency and operational stability of planar perovskite solar cells

SnO₂ is a promising alternative for TiO₂ electron transporting layer (ETL), owing to the high charge mobility and chemical stability. Defects accumulating at interfaces and grain boundaries are detrimental to the performance of perovskite solar cells (PSCs). Herein, a ligand-biphenyl-3,3′,5,5′-tetracarboxylic acid butyl amine (BPTC-BN) with four carbonyls and conjugated electron is used to passivate defects at SnO₂/perovskite interface. Meanwhile perovskite grown on SnO₂/BPTC-BN shows increased and uniform grain size. Benefitting from decreased defects at interface and bulk perovskite, a planar PSC with a power conversion efficiency (PCE) of 21.23% and an open voltage (V_OC) of 1.164 V is obtained. In contrast, devices based on single SnO₂ layers deliver a PCE of 19.38% and a V_OC of 1.114 V. In addition, this interface passivation strategy also improves device operational stability substantially, retaining 84% of its initial efficiency after 1000 h tracking at maximum power point (MPP). The results prove the prime importance of interface for the photovoltaic performance especially operational stability of PSCs.