Solution processed organic solar cells (OSCs) composed of all small molecules (ASM) are promising for production on an industrial scale owing to the properties of small molecules, such as well-defined chemical structures, high purity of materials, and outstanding repeatability from batch to batch synthesis. Remarkably, ASM OSCs with power conversion efficiency (PCE) beyond 13% were achieved by structure improvement of the electron donor and choosing Y6 as the electron acceptor. However, the fill factor (FF) is an obstacle that limits the further improvement of the PCE for these ASM OSCs. Herein, we focus on the FF improvement of recently reported ASM OSCs with BTR-Cl:Y6 as the active layer by miscibility-induced active layer morphology optimization. The incorporation of fullerene derivatives, which have good miscibility with both BTR-Cl and Y6, results in reduced bimolecular recombination and thus improved FF. In particular, when ca. 5 wt% of PC₇₁BM was added in the active layer, a FF of 77.11% was achieved without sacrificing the open circuit voltage (V_OC) and the short circuit current density (J_SC), leading to a record PCE of 15.34% (certified at 14.7%) for ASM OSCs. We found that the optimized device showed comparable charge extraction, longer charge carrier lifetime, and slower bimolecular recombination rate compared with those of the control devices (w/o fullerene). Our results demonstrate that the miscibility driven regulation of active layer morphology by incorporation of a fullerene derivative delicately optimizes the active layer microstructures and improves the device performance, which brings vibrancy to OSC research.

中文翻译：

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效率高达15.34％的全小分子有机太阳能电池，富勒烯添加剂可提高填充因子

由小分子（ASM）组成的固溶处理有机太阳能电池（OSC）由于具有小分子的特性（如定义明确的化学结构，高纯度的材料以及出色的批次重复性），有望在工业规模上生产批量合成。值得注意的是，通过改善电子给体的结构并选择Y6作为电子受体，可以实现功率转换效率（PCE）超过13％的ASM OSC 。但是，填充因子（FF）是阻碍这些ASM OSC的PCE进一步改进的障碍。在此，我们重点关注最近报道的带有BTR-Cl的ASM OSC的FF改善：Y6通过混溶诱导的活性层形态优化来作为活性层。与BTR-C1和Y6都具有良好混溶性的富勒烯衍生物的掺入导致双分子重组减少并因此改善了FF。特别是当ca。在有源层中添加5 wt％的PC ₇₁ BM，在不牺牲开路电压（V _OC）和短路电流密度（J _SC）的情况下，获得77.11％的FF。），导致ASM OSC的PCE达到创纪录的15.34％（认证为14.7％）。我们发现，与对照装置（不含富勒烯）相比，优化装置显示出可比的电荷提取，更长的载流子寿命和更慢的双分子重组速率。我们的结果表明，通过掺入富勒烯衍生物，可混溶性驱动活性层形态的调节可精细地优化活性层的微观结构并改善器件性能，这为OSC研究带来了活力。