The Impact of Donor-Acceptor Phase Separation on the Charge Carrier Dynamics in pBTTT:PCBM Photovoltaic Blends
The Impact of Donor-Acceptor Phase Separation on the Charge Carrier Dynamics in pBTTT:PCBM Photovoltaic Blends
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DOI：
10.1002/marc.201500112
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发表时间：
2015-06-01
影响因子：
4.6
通讯作者：
Laquai, Frederic
中科院分区：
文献类型：
--
作者：
Gehrig, Dominik W.;Howard, Ian A.;Laquai, Frederic
介绍了由供体-受体混合比控制的供体-受体相分离对 pBTTT-C14:PC70BM 本体异质结光伏共混物中电荷生成和复合动态的影响。瞬态吸收 (TA) 光谱覆盖可见光和近红外光谱区域从皮秒到微秒的动态范围，表明在 1:1 混合激子解离速度超快；然而，电荷无法完全摆脱它们相互的库仑吸引力，因此主要在亚纳秒时间尺度上重新组合。相比之下，1:4的聚合物:富勒烯混合比有利于形成空间分离的、即自由的电荷，并显着降低成对电荷复合的比例，进而导致更高效的光伏器件。这说明在超快时间尺度上分离电荷需要空间扩展的供体或受体域（
The effect of donor-acceptor phase separation, controlled by the donor-acceptor mixing ratio, on the charge generation and recombination dynamics in pBTTT-C14:PC70BM bulk heterojunction photovoltaic blends is presented. Transient absorption (TA) spectroscopy spanning the dynamic range from pico- to microseconds in the visible and near-infrared spectral regions reveals that in a 1:1 blend exciton dissociation is ultrafast; however, charges cannot entirely escape their mutual Coulomb attraction and thus predominantly recombine geminately on a sub-ns timescale. In contrast, a polymer:fullerene mixing ratio of 1:4 facilitates the formation of spatially separated, that is free, charges and reduces substantially the fraction of geminate charge recombination, in turn leading to much more efficient photovoltaic devices. This illustrates that spatially extended donor or acceptor domains are required for the separation of charges on an ultrafast timescale (