Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells
Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells
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DOI：
10.1038/s41467-020-18439-z
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发表时间：
2020-09-15
影响因子：
16.6
通讯作者：
Vandewal, Koen
中科院分区：
文献类型：
--
作者：
Dong, Yifan;Nikolis, Vasileios C.;Vandewal, Koen
有机太阳能电池通常利用给电子（D）和受电子（A）材料之间的异质结将激子分裂成电荷。然而，D-A 混合物的使用本质上限制了光电压并引入了形态不稳定。在这里，我们证明化学相同分子的多晶薄膜提供了一种有前途的替代方案，并表明 α-六噻吩 (α-6T) 薄膜的光激发可以有效产生电荷。这使得基于α-6T的同质结有机太阳能电池的外量子效率高达44%，开路电压为1.61 V。形态、光发射和建模研究表明，不同方向的α-6T晶域之间的边界产生界面能量偏移为0.4 eV的静电景观，促进界面处杂化激子/电荷转移态的形成，有效解离成自由电荷。我们的研究结果为有机太阳能电池设计开辟了新途径，通过分子静电工程和介观结构控制来调整材料能量。
Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of alpha-sexithiophene (alpha-6T) films results in efficient charge generation. This leads to alpha-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61 V. Morphological, photoemission, and modelling studies show that boundaries between alpha-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4 eV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control.