Nickel oxide morphology synthesized with a hydrothermal method for inverted perovskite solar cells

In this paper, a hydrothermal method was used to synthesize nickel oxide nanostructure (nano-NiO) for its application to the inverted perovskite solar cells. These pore nanostructures were employed to increase both the contact and the channel between the hole transport and the perovskite layers of a ITO/nano-NiO/CH3NH3PbI3/PCBM/Ag device. The purpose of this research is twofold. Firstly, three different nano-NiO morphologies were synthesized at the synthesis temperatures of 140℃, 160℃, and 180℃. Then, Raman spectrometer was used to check the phonon vibration and magnon scattering characteristics after an annealing temperature of 500℃. Secondly, the nano-NiO powders were dispersed in isopropanol for the subsequent spin coating on the inverted solar cells. The nano-NiO morphologies were multi-layer flakes, microspheres and particles at the synthesis temperatures of 140℃, 160℃, and 180℃, respectively. When the microsphere nano-NiO was used as the hole transport layer, the perovskite layer had a larger coverage of 83.9%. The grain size of the perovskite layer was analyzed by X-ray diffraction (XRD), and the strong crystal orientations of (110) and (220) peaks were found. Despite this, the power conversion efficiency could affect the promotion, which is 1.37 times higher than the PEDOT:PSS element conversion efficiency of the planar structure.