Centre for Plastic Electronics and Department of Chemistry, Imperial College London, South Kensington Campus, Exhibition Road, SW7 2AZ, U.K.
Sci Rep. 2013;3:1531. doi: 10.1038/srep01531.
The dissociation of photogenerated excitons and the subsequent spatial separation of the charges are of crucial importance to the design of efficient donor-acceptor heterojunction solar cells. While huge progress has been made in understanding charge generation at all-organic junctions, the process in hybrid organic:inorganic systems has barely been addressed. Here, we explore the influence of energetic driving force and local crystallinity on the efficiency of charge pair generation at hybrid organic:inorganic semiconductor heterojunctions. We use x-ray diffraction, photoluminescence quenching, transient absorption spectroscopy, photovoltaic device and electroluminescence measurements to demonstrate that the dissociation of photogenerated polaron pairs at hybrid heterojunctions is assisted by the presence of crystalline electron acceptor domains. We propose that such domains encourage delocalization of the geminate pair state. The present findings suggest that the requirement for a large driving energy for charge separation is relaxed when a more crystalline electron acceptor is used.
光生激子的离解和随后的电荷空间分离对于高效施主-受主异质结太阳能电池的设计至关重要。虽然在理解全有机结处的电荷产生方面已经取得了巨大进展，但在混合有机-无机系统中的过程几乎没有得到解决。在这里，我们探讨了在混合有机-无机半导体异质结中，能量驱动力和局部结晶度对电荷对生成效率的影响。我们使用 X 射线衍射、光致发光猝灭、瞬态吸收光谱、光伏器件和电致发光测量来证明，在混合异质结中，光生极化子对的离解是由结晶电子受体域的存在辅助的。我们提出，这样的域鼓励生对态的离域化。目前的研究结果表明，当使用更结晶的电子受体时，电荷分离所需的大驱动力的要求会放宽。
