Mangold Hannah, Bakulin Artem A, Howard Ian A, Kästner Christian, Egbe Daniel A M, Hoppe Harald, Laquai Frédéric
Max Planck Research Group for Organic Optoelectronics, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Phys Chem Chem Phys. 2014 Oct 14;16(38):20329-37. doi: 10.1039/c4cp01883d. Epub 2014 Jun 25.
Charge generation and recombination processes occurring in ternary photoactive copolymer:copolymer:fullerene blends consisting of different mixing ratios between entirely amorphous and semi-crystalline PPE-PPV copolymers are investigated by transient absorption pump-probe and pump-push photocurrent spectroscopy. The experiments reveal that an excess of semi-crystalline polymer facilitates exciton dissociation into free charge carriers, slows down geminate recombination, and suppresses non-geminate recombination leading to increased short-circuit currents and high fill factors. In contrast, blends utilizing solely the amorphous polymer for their donor phase suffer from a large fraction of sub-nanosecond geminate recombination of interfacially bound charge-transfer states and also from fast non-geminate recombination of free charges, resulting in a significantly reduced photovoltaic performance. However, small fractions of the amorphous polymer blended into the semi-crystalline polymer increase the open-circuit voltage and the fill factor, while keeping the charge generation and recombination parameters largely unaltered in turn leading to an optimized device performance for the ternary PPE-PPV copolymer:copolymer:fullerene blends.
通过瞬态吸收泵浦 - 探测和泵浦 - 推挽光电流光谱，研究了由完全无定形和半结晶PPE - PPV共聚物之间不同混合比例组成的三元光活性共聚物：共聚物：富勒烯共混物中发生的电荷产生和复合过程。实验表明，过量的半结晶聚合物有助于激子解离成自由电荷载流子，减缓成对复合，并抑制非成对复合，从而导致短路电流增加和填充因子提高。相比之下，仅使用无定形聚合物作为供体相的共混物，存在很大一部分界面结合电荷转移态的亚纳秒级成对复合，以及自由电荷的快速非成对复合，导致光伏性能显著降低。然而，混入半结晶聚合物中的少量无定形聚合物会增加开路电压和填充因子，同时使电荷产生和复合参数基本保持不变，进而为三元PPE - PPV共聚物：共聚物：富勒烯共混物带来优化的器件性能。
