Gasparini Nicola, Camargo Franco V A, Frühwald Stefan, Nagahara Tetsuhiko, Classen Andrej, Roland Steffen, Wadsworth Andrew, Gregoriou Vasilis G, Chochos Christos L, Neher Dieter, Salvador Michael, Baran Derya, McCulloch Iain, Görling Andreas, Lüer Larry, Cerullo Giulio, Brabec Christoph J
Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, UK.
Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich Alexander-University Erlangen-Nuremberg, Erlangen, Germany.
Nat Commun. 2021 Mar 19;12(1):1772. doi: 10.1038/s41467-021-22032-3.
A critical bottleneck for improving the performance of organic solar cells (OSC) is minimising non-radiative losses in the interfacial charge-transfer (CT) state via the formation of hybrid energetic states. This requires small energetic offsets often detrimental for high external quantum efficiency (EQE). Here, we obtain OSC with both non-radiative voltage losses (0.24 V) and photocurrent losses (EQE > 80%) simultaneously minimised. The interfacial CT states separate into free carriers with ≈40-ps time constant. We combine device and spectroscopic data to model the thermodynamics of charge separation and extraction, revealing that the relatively high performance of the devices arises from an optimal adjustment of the CT state energy, which determines how the available overall driving force is efficiently used to maximize both exciton splitting and charge separation. The model proposed is universal for donor:acceptor (D:A) with low driving forces and predicts which D:A will benefit from a morphology optimization for highly efficient OSC.
提高有机太阳能电池（OSC）性能的一个关键瓶颈是通过形成混合能量状态来最小化界面电荷转移（CT）状态下的非辐射损失。这需要较小的能量偏移，而这通常对高外部量子效率（EQE）不利。在此，我们获得了非辐射电压损失（0.24 V）和光电流损失（EQE > 80%）同时最小化的有机太阳能电池。界面CT状态以约40皮秒的时间常数分离为自由载流子。我们结合器件和光谱数据对电荷分离和提取的热力学进行建模，揭示器件的相对高性能源于CT状态能量的最佳调整，这决定了可用的总驱动力如何有效地用于最大化激子分裂和电荷分离。所提出的模型对于低驱动力的供体：受体（D:A）是通用的，并预测哪些D:A将受益于高效有机太阳能电池的形态优化。
