The properties of sol-gel processed indium-doped zinc oxide semiconductor film and its application in organic solar cells

Indium-doped ZnO (IZO) films with various indium contents were deposited by sol-gel process for application in organic solar cells (OSCs). X-ray photoelectron spectroscopy (XPS) spectrum verified that indium is incorporated in the ZnO films. All films showed polycrystalline nature with a hexagonal wurtzite structure of ZnO. The resistivity of the films initially decreases yet increases again with higher doping. The lowest resistivity of 5.54 x 10(-1) Omega-cm was obtained at 1 at.% indium-doped film. The optical transmittance of all films is above 80% in visible range and blue shift in absorption edge was observed upon indium doping. The humidity level influences surface morphology, electrical, and optical properties of the doped films due to the strong moisture absorption nature of indium doping precursor. The performance of inverted OSC employing 1 at.% IZO as a buffer layer is higher than that of cell using undoped ZnO, which can be attributed to the higher optical transmittance and lower resistivity of doped film. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim