Behavior of carrier transports and responsivity to solar irradiation for poly(3-hexylthiophene)/silicon devices with and without the insertion of silicon nanowires and the addition of black phosphorus

The effects of the insertion of the silicon nanowire (SiNW) array and the incorporation of black phosphorus (BP) powders into poly(3-hexylthiophene) (P3HT) on the behavior of carrier transports and the responsivity to solar irradiation for P3HT/n-type Si (n-Si) devices are studied. It is found that thermionic emission and space charge limited current influence the forward current-voltage characteristics of P3HT/n-type Si devices. However, for P3HT/SiNWs/n-Si or P3HT:BP/SiNWs/n-Si devices, carrier transport in the forward-voltage region is dominated by ohmic conduction. In contrast with the P3HT/n-Si device, the P3HT:BP/SiNWs/n-Si device exhibits the lower reflectance, poorer rectification behavior and higher responsivity to solar irradiation, indicating that the increased photocurrent density can be interpreted by the high external light injection efficiency and the high carrier mobility in the P3HT:BP layer.