Dual-site parallel binding ligands for enhanced perovskite solar cell efficiency

Abstract

Perovskite solar cells (PSCs) are promising in the field of photovoltaics but are hindered by surface defects and stability. However, the energetic losses occurring at the interfaces between the perovskite and the charge transport layers often lead to reduced power conversion efficiency (PCE). Surface treatment is an effective strategy but the passivating ligands usually bind with a single active site. The resulted dense packing of resistive passivators perpendicular to the surface is detrimental to charge transport. Here, we present a passivator that can bind to two neighboring lead (Ⅱ) ion (Pb²⁺) defect sites simultaneously with an aligned parallel mode to the perovskite surface, effectively suppressing the surface trap density and preventing the aggregation. The target device fulfills a PCE of 25.1% and maintains over 85% of the initial efficiency after 800 h of exposure to a relative humidity (RH) of 65% ± 5%.