On the Energetic Dependence of Charge Separation in Low-Band-Gap Polymer/Fullerene Blends
On the Energetic Dependence of Charge Separation in Low-Band-Gap Polymer/Fullerene Blends
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DOI：
10.1021/ja308177d
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发表时间：
2012-11-07
影响因子：
15
通讯作者：
Durrant, James R.
中科院分区：
文献类型：
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作者：
Dimitrov, Stoichko D.;Bakulin, Artem A.;Durrant, James R.
驱动供体/受体异质结之间的电荷分离所需的高能驱动力是有机光电器件的关键考虑因素。在此，我们报告了一系列的瞬态吸收和光电流的实验作为激发波长和温度的函数的两个低带隙聚合物/富勒烯共混物，研究在施主/受主界面的电荷分离的机制。对于表现出最小的供体/受体LUMO能级偏移的共混物，光电流量子产率福尔斯随着光子激发能量朝向带隙减小而下降，但是结合界面电荷转移态的产率上升。作为初始激子能量的函数的束缚电荷和自由电荷产生之间的这种相互作用提供了过量能量在驱动电荷分离中的作用的关键证据，该电荷分离与用于增强的太阳光收集的低带隙聚合物的发展直接相关。
The energetic driving force required to drive charge separation across donor/acceptor heterojunctions is a key consideration for organic optoelectronic devices. Herein we report a series of transient absorption and photocurrent experiments as a function of excitation wavelength and temperature for two low-band-gap polymer/fullerene blends to study the mechanism of charge separation at the donor/acceptor interface. For the blend that exhibits the smallest donor/acceptor LUMO energy level offset, the photocurrent quantum yield falls as the photon excitation energy is reduced toward the band gap, but the yield of bound, interfacial charge transfer states rises. This interplay between bound and free charge generation as a function of initial exciton energy provides key evidence for the role of excess energy in driving charge separation of direct relevance to the development of low-band-gap polymers for enhanced solar light harvesting.