Department of Chemistry, Energy Institute and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong.
Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, SE-58183, Sweden.
Adv Mater. 2018 Nov;30(45):e1804215. doi: 10.1002/adma.201804215. Epub 2018 Oct 1.
State-of-the-art organic solar cells (OSCs) typically suffer from large voltage loss (V ) compared to their inorganic and perovskite counterparts. There are some successful attempts to reduce the V by decreasing the energy offsets between the donor and acceptor materials, and the OSC community has demonstrated efficient systems with either small highest occupied molecular orbital (HOMO) offset or negligible lowest unoccupied molecular orbital (LUMO) offset between donors and acceptors. However, efficient OSCs based on a donor/acceptor system with both small HOMO and LUMO offsets have not been demonstrated simultaneously. In this work, an efficient nonfullerene OSC is reported based on a donor polymer named PffBT2T-TT and a small-molecular acceptor (O-IDTBR), which have identical bandgaps and close energy levels. The Fourier-transform photocurrent spectroscopy external quantum efficiency (FTPS-EQE) spectrum of the blend overlaps with those of neat PffBT2T-TT and O-IDTBR, indicating the small driving forces for both hole and electron transfer. Meanwhile, the OSCs exhibit a high electroluminescence quantum efficiency (EQE ) of ≈1 × 10 , which leads to a significantly minimized nonradiative V of 0.24 V. Despite the small driving forces and a low V , a maximum EQE of 67% and a high power conversion efficiency of 10.4% can still be achieved.
目前，与无机和钙钛矿太阳能电池相比，有机太阳能电池（OSC）通常存在较大的电压损失（V ）。人们已经尝试通过降低给体和受体材料之间的能量势垒来降低 V ，并且 OSC 领域已经展示了具有较小最高占据分子轨道（HOMO）势垒或给体和受体之间可忽略不计的最低未占据分子轨道（LUMO）势垒的高效系统。然而，基于给体/受体系统同时具有较小 HOMO 和 LUMO 势垒的高效 OSC 尚未得到证明。在这项工作中，报道了一种基于给体聚合物 PffBT2T-TT 和小分子受体（O-IDTBR）的高效非富勒烯 OSC，它们具有相同的能带隙和接近的能级。共混物的傅里叶变换光电流光谱外量子效率（FTPS-EQE）光谱与纯 PffBT2T-TT 和 O-IDTBR 的光谱重叠，表明空穴和电子转移的驱动力都很小。同时，OSC 表现出 ≈1×10 的高电致发光量子效率（EQE ），这导致非辐射 V 显著减小至 0.24V。尽管驱动力较小且 V 较低，但仍可以实现 67%的最大 EQE 和 10.4%的高光功率转换效率。
