Maximizing Photoluminescence Quantum Efficiency of Stacked Halide Layer for Highly Efficient Perovskite Solar Cells

To further approach the theoretical limit of perovskite solar cells (PSCs), it is cucial to analyze and interpret the external photoluminescence quantum efficiency (PLQE) of a light-absorbing halide layer stacked with charge transporting layers (CTLs) rather than solely as a halide layer. Here, we propose the next phase research direction for reaching radiative limit of PCE by maximzing PLQE of the stacked halide layer. We demonstrated that controlling the bottom charge transporting layer (CTL)/perovskite interface is a main factor to maximize PLQE in full device stack. On combining interface and bulk engineering, the FTO/bottom CTL/halide structure and full device stack exhibited an enhanced external photoluminescence quantum efficiency (PLQE) of 40.67% and 15.57%, respectively. As a result, the device combined with the interface and bulk engineering showed a certified quasi-steady-state (QSS) efficiency of 25.06%. The certified open-circuit voltage (Voc) of 1.18 V is 94.93% of the radiative limit Voc of 1.243 V, the highest value among certified QSS Voc of PSCs. This research approach provides a promising direction for reaching the theoretical limit of PSCs by maximizing PLQE.