Broad‐Spectral Response Lead Halide Perovskite Solar Cells Through Integration of Multifunctional Organic Bulk‐Heterojunction and Quantum‐Cutting Downconversion Materials

ABSTRACT Expanding near‐infrared (NIR) spectral response and utilizing ultraviolet (UV) photons are effective strategies for enhancing the power conversion efficiency (PCE) of lead halide perovskite solar cells (PSCs). However, the range of NIR spectral response extension and the utilization of UV light for devices are not enough, and the loss of photovoltaic performance caused by UV light‐induced degradation is still unavoidable. Herein, we develop a novel strategy by integrating a PTB7‐Th:COi8DFIC bulk heterojunction (BHJ) with perovskite layers to broaden the NIR spectral absorption range to 1050 nm. Meanwhile, the BHJ layer with a suitable energy level can effectively passivate defects, improve charge transport, and resist the erosion of moisture. The mechanism of UV light‐induced degradation in PSCs demonstrates that the evolution of microstructure results in a drastic decrease in photovoltaic parameters. For increasing UV utilization, a Y 2 O 3 :Bi 3+ , Yb 3+ film is introduced into the device to convert high‐energy photons in the UV region into lower‐energy photons in the visible and NIR regions by the quantum‐cutting effect. After synchronously broadening the NIR spectral absorption and improving the UV spectral response of the PSCs, the efficiency is considerably improved to 23.47%, and the short‐circuit current density is enhanced from 21.33 to 24.62 mA cm −2 . Upgraded devices exhibit excellent UV, humidity, and long‐term stability. This study explores a comprehensive strategy for obtaining high‐performance and stable broad‐spectral response PSCs.