Effects of a bathophenanthroline exciton blocking layer on thermal annealing-free bulk heterojunction solar cells

The effects of bathophenanthroline (Bphen) as an exciton blocking layer (EBL) on annealing-free bulk heterojunction solar cells were investigate. A nonannealed donor–acceptor conjugated polymer was employed as the donor to ensure the simplicity of device fabrication and good reproducibility of experimental results. By incorporating a 5 nm thick Bphen layer, a 30.3% enhancement in the power conversion efficiency (PCE), from 3.3% to 4.3%, can be achieved. Furthermore, impacts of the EBL thickness on device performance were analyzed. The significant improvement in PCE suggests Bphen as an ideal EBL material for organic photovoltaics free from thermal treatment.