论文标题
长期和无序的电荷转移状态可在有效的非富烯有机太阳能电池中实现吸热电荷分离
Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells
论文作者
论文摘要
尽管接近零的供体能量偏移量接近零供体能量，以驱动电荷分离并克服电子和孔之间的相互吸引力，但基于非富勒烯受体的有机太阳能电池（OSC）仍能显示出高电荷产生的产量。在这里，我们使用时间分辨的光谱法表明，这些系统中的自由电荷是通过热激活的界面电荷转移 - 转移激素激活的分离产生的，该分离发生在室温下在数百个Picseconds上发生，而三个尺寸的订单比可比的富勒烯系统慢了三个。在以后的时间遇到游离电子孔时，将重新生成CTE和发射激子，从而在激子，CTE和自由电荷之间建立平衡。这种吸热的电荷分离过程使这些系统能够接近准热动力平衡条件，而无需能量偏移以驱动电荷分离并实现极大抑制的非辐射重组。
Organic solar cells (OSCs) based on non-fullerene acceptors can show high charge generation yields despite near-zero donor-acceptor energy offsets to drive charge separation and overcome the mutual Coulomb attraction between electron and hole. Here we use time-resolved optical spectroscopy to show that free charges in these systems are generated by thermally activated dissociation of interfacial charge-transfer excitons (CTEs) that occurs over hundreds of picoseconds at room temperature, three orders of magnitude slower than comparable fullerene-based systems. Upon free electron-hole encounters at later times, CTEs and emissive excitons are regenerated, thus setting up an equilibrium between excitons, CTEs and free charges. This endothermic charge separation process enables these systems to operate close to quasi-thermodynamic equilibrium conditions with no requirement for energy offsets to drive charge separation and achieve greatly suppressed non-radiative recombination.
