Investigation of Cr³⁺ doped CuGaO₂ as an inorganic hole transport material (HTM) for perovskite solar cells

Perovskite Solar Cells (PSCs) are becoming feasible for developing effective energy harvesting devices. The biggest obstacles to their commercialization are the high price and lack of environmental sustainability of the organic hole transporting materials (HTMs). CuGaO₂ provides high coordination, stability, and low-temperature processing for effective and reliable PSCs. Here, a variety of solid solutions of CuGaO₂ and CuCrO₂ were created by a hydrothermal process to obtain the ideal composition that results in reliable size control and high hole conductivity employed for surface passivation at the perovskite contact. The composition ranges of CuGaO₂ doped with Cr³⁺ were CuGa_1-xCr_xO₂ (0 ≤ x ≤ 1, CuGaO₂). XRD patterns were obtained for the particles of various compositions, these (006), (012), (104) and (024) having 2θ values 33.23°, 36.48°, 43.43°, and 50.43° peaks were identified without the appearance of any impurity peaks. SEM micrographs of Cr³⁺ doped Copper Gallium Oxide depict a quasi-spherical structure and a quasi-hexagonal plate-like shape. The optical properties of nanoparticles were studied using UV–visible spectroscopy that showed the bandgap of CuGaO₂ was decreased from 3.32 eV to 3.05 eV. The chemical properties of nanoparticles were studied by using FTIR indicating the presence of metal oxide groups of bending and stretching vibrations. From J-V curves of the prepared perovskite solar cell devices, the device with 30 % of Cr doped CuGaO₂ achieves a PCE of 16.9 %, much higher than the reference samples without Cr doping.