Efficient optical absorption enhancement in organic solar cells by using a 2-dimensional periodic light trapping structure

We have investigated the effects induced by periodic nanosphere arrays on the performance of organic solar cells (OSCs). Two-dimensional periodic arrays of polystyrene nanospheres were formed by using a colloidal lithography method together with plasma etching to trim down the size to various degrees on the substrates of OSCs. It is found that the devices prepared on such substrates can have improved light harvesting, resulting in as high as 35% enhancement in power conversion efficiency over that of the reference devices. The measured external quantum efficiency and finite-difference time-domain simulation reveal that the controlled periodic morphology of the substrate can efficiently increase light scattering in the device and thus enhance the absorption of incident light.