Small molecule organic solar cells (SMOSCs) have received considerable attention in recent years. However, one of the key factors limiting the performance of SMOSCs is their large energy loss (E_loss), which is typically between 0.6 and 1.0 eV, and therefore significantly higher than those of perovskite solar cells and inorganic solar cells (E_loss < 0.5 eV). Herein, we successfully report a new acceptor–donor–acceptor (A–D–A) type dimeric squaraine electron donor (D-IDTT-SQ) with a low optical band gap of 1.49 eV and deep HOMO energy level of −5.20 eV. Consequently, a high open-circuit voltage (V_oc) of 0.93 V with an impressive power conversion efficiency (PCE) of 7.05% is achieved for solution-processed bulk heterojunction SMOSCs, showing an E_loss of only 0.56 eV. This is the first report wherein SMOSCs result in such a low E_loss, while simultaneously exhibiting a considerably high V_oc over 0.9 V and an excellent PCE above 7.0%.

中文翻译：

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适用于高效有机太阳能电池的低带隙小分子，其能量损失低于0.6 eV，开路电压超过0.9 V

近年来，小分子有机太阳能电池（SMOSC）受到了相当大的关注。但是，限制SMOSC性能的关键因素之一是其大的能量损耗（E _loss），通常在0.6至1.0 eV之间，因此大大高于钙钛矿太阳能电池和无机太阳能电池的能量损耗（E _loss <0.5 eV）。在这里，我们成功地报道了一种新的受体-供体-受体（A–D–A）型二聚方酸电子供体（D-IDTT-SQ），其光学带隙低，为1.49 eV，深HOMO能级为-5.20 eV。因此，高的开路电压（V _oc对于固溶异质结SMOSC，实现0.93 V的）功率转换效率（PCE）为7.05％，令人印象深刻，其E_损耗仅为0.56 eV。这是第一个报告，其中SMOSC导致如此低的E_损耗，同时在0.9 V以上的电压下呈现出相当高的V _oc，而在7.0％以上的电压下则具有出色的PCE。