Model Passivation Films for Photovoltaic Applications

John T. Yates, Jr

Department of Chemistry, College of Arts & Sciences, UVa

Mool C. Gupta

Department of Electrical and Computer Engineering, School of Engineering and Applied Science, UVa

TiO_x thin films are considered for the photovoltaic applications in terms of the surface passivation and the long-term durability of devices. Transmission infrared spectroscopy will be employed to study the mode of surface passivation by TiO_x thin films made by hydrolysis of titanium isopropoxide. A hypothesis that radical species are made by photodecomposition of residual titanium isoproxide groups in the film will be tested by exposure to UV irradiation, followed by infrared spectroscopy. In addition, using UV absorption spectroscopy, the development of the bandgap of the TiO_x film will be followed as the thermal loss of isopropoxide species takes place and more highly organized TiO₂ structures are formed in the film. The reactivity toward oxygen and water vapor of the photoproduced species in the TiOx film will be studied. Parallel studies of the ability of TiO_x films to passivate laboratory-made photovoltaic cells against oxygen and water vapor as well the electrical charge will be carried out. The impact of TiO_x film on charge carrier life-time and solar cell quantum efficiency will be examined.