Synergistic passivation with multi-dentate 2,6-pyridinedicarboxylic acid for high-performance perovskite solar cells

Abstract

Organic hybrid metal halide perovskite solar cells (PSCs) are considered a promising photovoltaic technique, because of their strikingly optoelectronic characteristics and simple fabrication process. Nevertheless, numerous electronic defects within the perovskite film as carrier-trapping centers and ionic migration pathways can seriously affect the power conversion efficiency (PCE) and stability of PSCs. Defect passivation is one of the most facile and effective concepts to heal these electronic defects and can efficiently improve the performance of PSCs. Here, multi-dentate 2,6-pyridinedicarboxylic acid (2,6-PDA) was first employed as a passivating agent to synergistically decrease electronic defects in the polycrystalline perovskite film. The carboxyl and pyridyl groups of 2,6-PDA acting as a Lewis base can donate electron pairs to the uncoordinated Pb²⁺ ions, thereby healing the Pb²⁺ defects, while the hydroxyl group can interact with the I⁻ of the perovskite film via O–H⋯I hydrogen bond to inhibit the I⁻ ion migration. The results exhibited that an improved PSC with the highest PCE of 20.57% and significantly more stability could be achieved after 2,6-PDA passivation in comparison with the control PSC (18.14% PCE). The synergistic passivation process developed and described in this work offers meaningful guidance for the future exploration of new multi-functional organic molecules to heal the electronic defects of PSCs for improving their performance and stability.