Multi‐Facet Passivation of Ternary Colloidal Quantum Dot Enabled by Quadruple‐Ligand Ensemble toward Efficient Lead‐Free Optoelectronics

Abstract

Solution‐processed ternary‐compound semiconductor AgBiS2 colloidal quantum dots (CQDs) are promising light‐absorbing materials owing to their nontoxicity and high absorption coefficient (>106 cm−1). However, rational strategies to passivate multi‐facet of ternary‐compound CQDs and manufacture stable CQD inks have not yet been proposed. In this paper, a ligand passivation strategy is proposed using a solution‐phase ligand exchange method. A quadruple‐ligand ensemble is employed to demonstrate multifaceted passivation on AgBiS2 CQDs and a highly stable CQD ink. Density functional theory studies reveal the secondary cation adsorption of silver halide passivation, indicating the synergistic passivation of the ligand ensemble. This yields a low trap density in CQD solids, improving the power conversion efficiency to 8.1% by 53% in CQD solar cells. Furthermore, the proposed device exhibits the fastest response time of 400 ns among all reported AgBiS2 devices, demonstrating its potential for efficient lead‐free optoelectronics.