Dual-anchored configuration involving Pb(NO3)2 for effective and stable FAPbI3 quantum dot solar cells

Abstract

The dynamic nature of formamidine lead iodide quantum dots (FAPbI₃ QDs) limits their practical application by causing the appearance of ionic vacancy defects on the surface of QDs, which would then allow for significant trap-assisted non-radiative recombination of charge carriers. Herein, we explore a feasible surface modification strategy for passivating vacancy defects. Different lead salts are employed in the post-treatment procedure of quantum dot films. Based on both experimental and theoretical findings, Pb(NO₃)₂ passivation comprises Pb²⁺ and FA⁺. On the quantum dot surface, the O atoms from NO⁻₃ form strong chemical bonds with FA⁺, and the O–C⋯O–N structure, defined by a dual-anchored configuration, contributes to the establishment of a stable crystal structure by exhibiting optimal bond lengths (3.486 Å and 3.775 Å, respectively) and a higher binding energy (10.51 eV). Finally, FAPbI₃ quantum dot solar cells simultaneously achieve both exceptional environmental stability and a champion photoelectric conversion efficiency of 12.11%. This work provides valuable insights into surface chemical engineering of quantum dots, paving the way for high-performing photovoltaic devices.