Organic semiconductors can potentially revolutionize solar cell technology by offering very thin, lightweight, and flexible modules for outdoor and indoor power generation. Light absorption in organic semiconductors generates a bound electron-hole pair (exciton), which needs to travel to the interface between electron donor and acceptor materials to dissociate into charge carriers. Because the exciton diffusion length in organic semiconductors is typically much shorter than the light absorption depth (∼100 nm), planar donor-acceptor heterojunctions are inefficient, and most effort has been dedicated to optimization of bulk heterojunctions with nanoscale phase separation. In this Perspective, we review recent findings and new approaches to increase the exciton diffusion length and discuss how these improvements can benefit environmentally friendly production of solar modules using organic nanoparticles or graded heterojunctions obtained by sequential deposition of electron donor and acceptor.

有机半导体可以为户外和室内发电提供超薄，轻巧和灵活的模块，从而有可能彻底改变太阳能电池技术。有机半导体中的光吸收会产生束缚的电子-空穴对（激子），该对电子-空穴对需要传播到电子供体和受体材料之间的界面以解离为电荷载流子。由于有机半导体中的激子扩散长度通常比光吸收深度（〜100 nm）短得多，因此平面施主-受体异质结效率低下，并且大多数工作已致力于通过纳米级相分离优化体相异质结。从这个角度来看，