Abstract:
Chemical bath deposition method was used to grow Nickel doped ZnO (Ni-ZnO) thin films on a seed layer grown using the conventional spray pyrolysis method. Structural, optical and electrical properties were studied at different doping levels of Ni (0, 2, 4, 6 and 8 %) to the molar concentration of ZnO. All samples exhibited a highly defined (002) peak indicating a strong hexagonal crystal structure orientation. Samples with low levels of the dopant indicated lower mean roughness values. The grain size decreased from 167 nm for pure ZnO to lowest of 79 nm at 2% Ni concentration. Optical and electrical properties showed an optimum value at 2% Ni concentration. The 2% Ni-ZnO film was then used to fabricate a perovskite solar cell of the order FTO/NiZnO/MgOEA/Dye/Perovskite/Carbon/FTO. XRD analysis was
performed to confirm the Ni-ZnO/MgO structure of the ETL. The dye treated FTO/Ni-
ZnO/MgO layers were evaluated for their optical properties. The untreated ethanolamine (EA) layer showed higher transmittance followed by rosebengal (RB) and brilliant Black BN (BBBN) treated layers respectively. The transmittance was observed to be on the range 40% to 60% within the visible spectral range. The obtained band gap values for the dye treated samples were found to be in the range 3.05-3.06 (eV). Electrical properties of FTO/Ni-ZnO/MgO-EA/Dye were studied. High conductivity measurements where obtained from the BBBN treated sample at 1.26*103 (1/Ωcm) followed by EA at 1.03*103 (1/Ωcm) and RB at 9.9*102(1/Ωcm). From the I-V properties of the solar cells it was observed that RB treated layer produced higher efficiency of 0.0056% compared to the untreated EA (0.0043%) and BBBN (0.001%) respectively. The RB dye increased the solar cell Voc from 0.090V (EA) to 0.12V while the BBBN drastically reduced the Voc to 0.02 V. However, the BBBN-treated cell maintained higher Isc current of 0.193 mA in the proximity of untreated EA which produced 0.203 mA compared to RB which reduced Isc to 0.134 mA. Among the three samples, RB-treated sample produced higher fill factor (FF) ratio of 0.53 which corresponds to higher photoelectric power conversion rate of 0.00560 mW/cm2 followed by untreated EA with FF (0.37) corresponding to 0.00430 mW/cm2 and lastly BBBN with FF of 0.40 corresponding to 0.00119 mW/cm2. In overall the RB treated solar cell showed better results compared to the other samples.
