Ternary absorber blends have recently been identified as promising concepts to spectrally broaden the absorption of organic bulk-heterojunction solar cells and hence to improve their power conversion efficiencies. In this work, we demonstrate that D-D-A ternary blends comprising two donor polymers and the acceptor PC₆₁BM can also significantly enhance the thermal stability of the solar cell. Upon harsh thermal stress at 120 °C for 2 h, the ternary solar cells show only a minor relative deterioration of 10%. Whereas the polymer/fullerene blend PTB7-Th:PC₆₁BM is rather unstable under these conditions, its degradation was efficiently suppressed by incorporating the near infrared-absorbing polymer PDTP–DFBT. Spectroscopic ellipsometry investigations and an effective medium analysis of the ternary absorber blend revealed that the domain conformation in presence of PDTP–DFBT remains stable whereas the domain conformation changes in its absence. The ternary PTB7-Th:PDTP–DFBT:PC₆₁BM solar cells yield thermally stable power conversion efficiencies of up to 6%.

三元吸收剂共混物最近被认为是有前途的概念，可以在光谱上拓宽有机体-异质结太阳能电池的吸收范围，从而提高其功率转换效率。在这项工作中，我们证明了包含两种供体聚合物和受体PC ₆₁ BM的DDA三元共混物也可以显着提高太阳能电池的热稳定性。在120°C下持续2 h的苛刻热应力后，三元太阳能电池仅表现出10％的相对较小的劣化。聚合物/富勒烯共混物PTB7-Th：PC ₆₁在这些条件下，BM相当不稳定，通过掺入近红外吸收性聚合物PDTP-DFBT有效抑制了BM的降解。椭圆偏振光谱分析和三元吸收剂混合物的有效介质分析表明，在存在PDTP-DFBT的情况下，结构域构象保持稳定，而在不存在PDTP-DFBT的情况下，构象域发生变化。三元PTB7-Th：PDTP–DFBT：PC ₆₁ BM太阳能电池具有高达6％的热稳定功率转换效率。