Impact of Marginal Exciton-Charge-Transfer State Offset on Charge Generation and Recombination in Polymer:Fullerene Solar Cells
Impact of Marginal Exciton-Charge-Transfer State Offset on Charge Generation and Recombination in Polymer:Fullerene Solar Cells
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DOI：
10.1021/acsenergylett.9b01368
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发表时间：
2019-09-01
影响因子：
22
通讯作者：
Nelson, Jenny
中科院分区：
文献类型：
--
作者：
Vezie, Michelle S.;Azzouzi, Mohammed;Nelson, Jenny
有机异质结太阳电池的初始光激发态与电荷转移(CT)态之间的能量偏移对电荷产生和开路电压(V-oc)都有影响。在这里，我们使用时间分辨光谱和电压损失测量来分析激子-CT态偏移对低带隙聚合物(INDT-S)与不同电子亲和力的富勒烯衍生物(PCBM和KL)共混物中电荷转移、分离和复合过程的影响。对于低激子-CT态偏置混合物(IndT-S：PCBM)，光电流产生和非辐射电压损失都较低。InDT-S：PCBM共混物表现出不同的激发态动力学，这取决于施主或受主是否是光激发的。令人惊讶的是，在施主激发下，IndT-S：PCBM的电荷复合动力学明显快于IndT-S：KL。我们使用动力学模型和考虑最低激子态和CT态之间的杂交来协调这些观察结果。模拟结果表明，这种杂化可以在保持合理的电荷产生效率的同时，显著降低伏安损耗。
The energetic offset between the initial photo excited state and charge-transfer (CT) state in organic heterojunction solar cells influences both charge generation and open-circuit voltage (V-oc). Here, we use time-resolved spectroscopy and voltage loss measurements to analyze the effect of the exciton-CT state offset on charge transfer, separation, and recombination processes in blends of a low-band-gap polymer (INDT-S) with fullerene derivatives of different electron affinity (PCBM and KL). For the lower exciton-CT state offset blend (INDT-S:PCBM), both photocurrent generation and non-radiative voltage losses are lower. The INDT-S:PCBM blend shows different excited-state dynamics depending on whether the donor or acceptor is photoexcited. Surprisingly, the charge recombination dynamics in INDT-S:PCBM are distinctly faster than those in INDT-S:KL upon excitation of the donor. We reconcile these observations using a kinetic model and by considering hybridization between the lowest excitonic and CT states. The modeling results show that this hybridization can significantly reduce V-oc losses while still allowing reasonable charge generation efficiency.