Ternary organic solar cells (TOSC) are currently under intensive investigation, recently reaching a record efficiency of 17.1%. The origin of the device open‐circuit voltage (VOC), already a multifaceted issue in binary OSC, is even more complex in TOSCs. Herein, two ternary systems are investigated with one donor (D) and two acceptor materials (A1, A2) including fullerene and nonfullerene acceptors. By varying the ratio between the two acceptors, VOC is found to be gradually tuned between those of the two binary systems, D:A1 and D:A2. To investigate the origin of this change, ultraviolet photoemission spectroscopy (UPS) depth profiling is employed, which is used to estimate the photovoltaic gap in the ternary systems. The results reveal an excellent agreement between the estimated photovoltaic gap and the VOC for all mixing ratios, suggesting that the energetic alignment between the blend components varies depending on the ratio D:A1:A2. Furthermore, the results indicate that the sum of radiative and nonradiative losses in these ternary systems is independent of the blend composition. Finally, the superiority of UPS over X‐ray photoemission spectroscopy (XPS) depth profiling is demonstrated in resolving compositional profiles for material combinations with very similar chemical, but dissimilar electronic structures, as common in TOSCs.

中文翻译：

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三元有机太阳能电池的能级对准

三元有机太阳能电池（TOSC）目前正在深入研究中，最近达到了创纪录的17.1％的效率。设备开路电压（VOC）的起源在二进制OSC中已经是多方面的问题，而在TOSC中则更为复杂。在本文中，研究了两个三元系统，其中一个供体（D）和两个受体材料（A1，A2）包括富勒烯和非富勒烯受体。通过改变两个受体之间的比例，发现VOC逐渐在两个二元体系D：A1和D：A2的VOC之间调整。为了研究这种变化的起因，采用了紫外光发射光谱（UPS）深度剖析，该深度剖析用于估算三元系统中的光伏间隙。结果表明，在所有混合比例下，估算的光伏间隙与VOC之间都具有极好的一致性，这表明共混物组分之间的能量取向取决于比率D：A1：A2。此外，结果表明这些三元体系中的辐射损耗和非辐射损耗之和与共混物的组成无关。最后，UPS在X射线光电子能谱（XPS）深度分析中的优越性在解析具有非常相似的化学但不相似的电子结构的材料组合的成分分布中得到了证明，这在TOSC中很常见。