Light Management for Fullerene-Based Semitransparent Polymer Solar Cells with a Distributed Bragg Reflector

Semitransparent organic photovoltaic devices (ST-OPVs) are a type of organic solar cells that can collect solar energy while maintaining transparency in the visible band. Their transparency allows ST-OPVs to be integrated into the exteriors of buildings, serving as solar windows. However, these devices often face the challenge of balancing high transparency with optimal efficiency. To mitigate this issue, we propose ST-OPVs constructed with a distributed Bragg reflector structure to improve the harvest of near-infrared energy, resulting in an increase in power conversion efficiency and near-infrared external quantum efficiency while maintaining considerable visible transmission. Although nonfullerene-based OPVs show much higher efficiency than conventional fullerene-based ones, they usually absorb visible light more intensively. Hu, Z. J. Mater. Chem. A 2021, 9, 6797–6804; Zhu, L. Nat. Mater. 2022, 21, 656–663; Li, C. Nat. Energy 2021, 6, 605–613 Here, we utilized a near-infrared (NIR) polymer donor PDTP-DFBT along with fullerene derivatives as an active layer in the ST-OPVs. Our devices demonstrated a notable light utilization efficiency (LUE) of 2.62% and an average visible transmission (AVT) of 51.6% for the PDTP-DFBT:PC60BM ST-OPVs. Similarly, the PDTP-DFBT:PC70BM ST-OPVs achieved an LUE of 2.35% while maintaining an AVT of 39%. Additionally, our ST-OPVs exhibit perfect color fidelity. Our research provides a viable solution for the utilization of solar energy in visibly transparent scenarios.