In Situ PL Tracking of Halide Exchange at 3D/QD Heterojunction Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) show promise for future photovoltaic technology. However, it faces challenges in terms of environmental stability. To address this, researchers have proposed nanomaterials such as perovskite quantum dots (QDs) to passivate the perovskite interfaces and enhance their stability. We explore the halide exchange reaction at the heterojunction between QDs and bulk (3D) perovskites using in situ photoluminescence. By determining the activation energy for the interfacial bromide-to-iodide exchange, we find that it is effective in passivating the 3D surface defects and grain boundaries. When applied in solar cells, QDs have energy level realignment, improving hole extraction and blocking electron transfer, which reduces bimolecular charge carrier recombination, thus increasing efficiency. The interfacial halide composition remains stable under thermal stress, and the QDs' ligand hydrophobicity was found to prevent moisture permeation within the perovskite films. Thus, strategically incorporating QDs enhances photovoltaic performance and has the potential to mitigate moisture and thermal-induced degradation.