Future Technology Research Center , Corporate R&D, LG Chem/LG Science Park , 30, Magokjungang 10-ro , Gangseo-gu , Seoul 07796 , Republic of Korea.
Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea.
ACS Appl Mater Interfaces. 2019 Feb 20;11(7):7208-7215. doi: 10.1021/acsami.8b20884. Epub 2019 Feb 12.
In the field of organic solar cells, it has been generally accepted until recently that a difference in band energies of at least 0.3 eV between the highest occupied molecular orbital (HOMO) level of the donor and the HOMO of the acceptor is required to provide adequate driving force for efficient photoinduced hole transfer due to the large binding energy of excitons in organic materials. In this work, we investigate polymeric donor:non-fullerene acceptor junctions in binary and ternary blend polymer solar cells, which exhibit efficient photoinduced hole transfer despite negligible HOMO offset and demonstrate that hole transfer in this system is dependent on morphology. The morphology of the organic blend was gradually tuned by controlling the amount of ITIC and PCBM. High external quantum efficiency was achieved at long wavelengths, despite ITIC-to-PCBM ratio of 1:9, which indicates efficient photoinduced hole transfer from ITIC to the donor despite an undesirable HOMO energy offset. Transient absorption spectra further confirm that hole transfer from ITIC to the donor becomes more efficient upon optimizing the morphology of the ternary blend compared to that of donor:ITIC binary blend.
在有机太阳能电池领域，直到最近人们普遍认为，为了提供有效的光致空穴转移驱动力，供体的最高占据分子轨道（HOMO）能级与受体的 HOMO 能级之间的能带能量差至少需要 0.3eV，这是由于有机材料中激子的结合能很大。在这项工作中，我们研究了二元和三元共混聚合物太阳能电池中的聚合物给体：非富勒烯受体结，尽管 HOMO 偏移可以忽略不计，但它们表现出有效的光致空穴转移，并且证明该体系中的空穴转移取决于形态。通过控制 ITIC 和 PCBM 的量逐渐调整有机共混物的形态。尽管 ITIC 与 PCBM 的比例为 1:9，但在长波长处仍实现了高外部量子效率，这表明尽管 HOMO 能量偏移不理想，但从 ITIC 到给体的光致空穴转移是有效的。瞬态吸收光谱进一步证实，与二元给体：ITIC 共混物相比，优化三元共混物的形态可使 ITIC 向给体的空穴转移更有效。
