Conjugated Polymer-Driven Compact Crystal Packing and Efficient Charge Transport in Perovskite Quantum Dot Solar Cells

Abstract

The stability and performance of perovskite quantum dot (PQD) solar cells are often compromised due to surface defects, phase transitions under ambient conditions, and inefficient charge transport caused by random packing and long-chain insulating ligands. This study introduces a conjugated polymer ligand strategy to simultaneously address these challenges by enhancing both charge transport and nanocrystal packing orientation. Unlike conventional insulating ligands, these conjugated polymers exhibit strong interaction with PQD surfaces while facilitating preferred PQD packing through pi-pi stacking interactions, a mechanism previously unexplored in PQD assemblies. Functionalized with ethylene glycol side chains, these polymers effectively reduce defect density, improve crystallinity, and enhance inter-dot coupling, leading to superior charge transport pathways. As a result, devices incorporating these polymers achieve a significantly improved maximum power conversion efficiency of over 15%, compared to 12.7% for pristine devices, with notable enhancements in short-circuit current density and fill factor. Furthermore, these devices demonstrate exceptional stability, retaining over 85% of their initial efficiency after 850 h. These findings establish conjugated polymer ligands as a dual-functional strategy for passivation and controlled PQD assembly, unlocking new pathways for high-performance and stable PQD solar cells suitable for real-world optoelectronic applications.