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

•We report the introduction of Bphen as an EBL into annealing-free BHJ solar cells (PCDTBT:PC61BM).•The impacts of Bphen layer thickness on device performance were investigated.•With the optimal thickness (5 nm) of Bphen layer, the most significant improvement in PCE was obtained from 3.3% to 4.3%.

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.