Regulating coordination by multi-configurational alkaloid-based passivation molecules for high-performance perovskite photovoltaics

Abstract

Abundant defects in polycrystalline perovskite will destroy the photovoltaic performance and accelerate the degradation of perovskite solar cells (PSCs). The development of effective management for multiple defects is obviously important to promote the practical application of perovskite photovoltaics. Herein, we firstly introduced the strategy of employing natural alkaloid passivation agents (adenine and cytosine) to achieve the directed management of lead- and iodide-based defects. Owing to the various configurations of alkaloid molecules, the electron cloud density distributions for different functional groups display adjustable characteristic, which closely related to the passivation effect. As a result, the CO with high electron density can form stronger Pb-O coordination with uncoordinated Pb2+ rather than the Pb-N bond (imidazole ring with Pb2+), leading to fewer lead-based defects being generated. The stronger electron-withdrawing ability of the CO further promotes the hydrogen bond of –NH2 and I-/Br- to reduce I-/Br- vacancies. Finally, the devices with cytosine perform the champion PCE of 22.07 % and dramatically enhance open-circuit voltage (Voc = 1.19 V), as well as much better environmental stability. This work provides a new insight on rationally design the non-toxic, cheap and accessible passivation molecules structure for achieving the efficient and stable PSCs.