Effect of Transition Metal Doping in the ZnO Nanorod on the Efficiency of the Electron Transport Layer in Semitransparent CsPbBr₃ Perovskite Solar Cells

We have grown vertically ZnO nanorods (NRs) doped withCu and Nito modulate their electronic properties. The wurtzite structure ofthe ZnO NRs was confirmed from the top-view field emission scanningelectron microscopy (FESEM) and atomic force microscopy (AFM) imagesas well as X-ray diffraction (XRD) spectra, and the phase purity wasconfirmed by Raman spectroscopy. The NRs exhibit high texture orientationin the (002) and (100) directions of the Ni- and Cu-doped ZnO NRs,respectively. This structural modification significantly modulatestheir electronic properties. Scanning tunneling spectroscopy (STS)and corresponding density of states (DOS) measurements were employedto determine the electronic band gap and band-edge shift of the dopedZnO NRs. Ambient-processed semitransparent CsPbBr3 perovskitesolar cells (PSCs) were fabricated with the device structure (FTO/ZnOseed layer/ZnO NRs:CsPbBr3/Spiro-MeOTAD/ITO) using theseNRs as the electron transport layer (ETL). The Ni-doped ZnO NR sampleswere found to be very good in electrical conductivity with a low electronicband gap, which yielded a device power conversion efficiency (PCE)of 4.94% under ambient conditions. Thus, Ni-doped ZnO NRs could beused as an efficient low-cost and ambient-processed one-dimensionalETL in the fabrication of optoelectronic devices.