Deposition of zinc oxide films by DC sputtering and its application as electron transport layer in inverted organic solar cell

DC sputtering method is employed to deposit Zinc Oxide films (ZnO) on glass substrates in Oxygen ambiance. The deposited film showed preferable orientation 101 with poor crystalline nature. The thickness of the film was found to be 525nm and sheet resistance was measured as 8kΩ/square. The UV-Visible spectroscopy investigations on the sample suggested that the sample is highly transparent over the visible region with a maximum transmission of 97% at 600nm. The absorption coefficient and refractive index values for different wavelengths are calculated. The band gap of the film is found to be 3.56eV from the (αhν)2--Energy plot. The obtained optical data of the sample is used to conduct Electron Transport Layer effect simulation studies in Inverted organic solar cell using GPVDM. The Inverted organic solar cell device is designed with P3HT:PCBM as active layer, PDOT:PSS/Ag as anode and ZnO/ITO as cathode. The studies revealed the optimum value of active layer thickness to be 175nm. Also, the best efficiency of 4.08% is derived by the device when the ZnO layer thickness was 50nm. Also, the device gave an efficiency of 4.09% for ZnO/FTO electrode structure.