Fe3O4 nanoparticles induced magnetic field effect on efficiency enhancement of P3HT:PCBM bulk heterojunction polymer solar cells

Fe3O4 magnetic nanoparticles (mean size of about 10 nm) capped by surfactant oleic acid (OA) were incorporated into P3HT:PCBM BHJ-PSCs by doping in the P3HT:PCBM photoactive layer for the first time. The PCE of the OA-Fe3O4:P3HT:PCBM BHJ-PSC device is enhanced by ∼18% at the optimum OA-Fe3O4 NPs doping ratio of 1%. The role of the magnetic property of Fe3O4 NPs on the PCE of OA-Fe3O4:P3HT:PCBM devices was studied, confirming the exclusive contribution of the Fe3O4 NPs to the observed enhancement of PCE. The enhancement of the PCE of the OA-Fe3O4:P3HT:PCBM BHJ-PSC device is found to be primarily due to the increase of short-circuit current (Jsc) by ∼14%, which is attributed to the magnetic field effect originated from the superparamagnetism of Fe3O4 NPs, resulting in the increase of the population of triplet excitons. Finally, the effect of Fe3O4 NPs on the enhancement of PCE of OA-Fe3O4:P3HT:PCBM device is further investigated by comparing different means of doping in P3HT:PCBM or PEDOT:PSS layer, confirming that such an effect can be achieved only when Fe3O4 NPs are doped in the P3HT:PCBM photoactive layer.