Perovskite-based solar cells with nickel-oxidized nickel oxide hole transfer layer

We demonstrated the methylammonium lead iodide (CH₃NH₃PbI₃) perovskite-based solar cells (SCs) with nickel (Ni)-oxidized nickel oxide (NiO_x) hole transport layer. The CH3NH3PbI3 perovskite-based SCs with Ni-oxidized NiO_x have better short-circuit current density ( JSC), open circuit voltage (VOC), and conversion efficiency (η%) than poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). In addition, the transmittance and work function increased with increasing oxidation temperature of Ni-oxidized NiO_x layer. The larger transmittance and work function of Ni-oxidized NiO_x could result in less light absorption and hole transport energy loss, respectively. Furthermore, Ni-oxidized NiO_x at 450 °C shows the smoothest surface morphology, which could result in the spin-coated CH₃NH₃PbI₃ perovskite film to have better crystal quality. Therefore, the SCs with 450 °C Ni-oxidized NiO_x hole transport show the largest η% of 7.75% that is ∼1.78 times larger than that of SCs with PEDOT:PSS hole transport layer.