Self-organized crystallinity paves the way to novel all-polymer solar cell
The crucial property of a BHJ is a self-organized interspersed network of donor and acceptor materials that transport the charge produced by the absorption of sunlight to the respective electrodes. In semiconducting molecules and polymers the charge splitting works via a bound electron-hole pair, a so-called exciton. The exciton has a finite lifetime corresponding to a diffusion length of only 10 nm, before it recombines, and thus the exciton has to reach a donor-acceptor interface within this range; otherwise it will not contribute to the photo current.