Opto-Electrical Study of Spectrally Enhanced Thin Film Solar Devices

S. Hajimirza, J.R. Howell
The University of Texas at Austin, US

Keywords: solar device, opto-electrical simulation, optimization


We report optical and electrical study of a light trapping for efficiency enhancement in thin film amorphous silicon. Solar absorption can be improved inside thin films via surface texturing, plasmonic excitations and thin anti-reflecting coating. These effects can be studied via numerical solutions of Maxwells equations and can be used for optimizing of light trapping. To determine the real world solar-to-electrical energy conversion rate of a PV cell, the more comprehensive study is however needed that takes in to account carrier recombination and contact shadowing. These interactions are modeled by the drift-diffusion equations. In this work, we study the opto-electrical design of a silicon-based thin film cell for maximal efficiency rate. The cell structure is composed of periodic plasmonic surface gratings and ITO coating. The parameters of the optimization include the gratings width, height and pitch, as well as the thickness of coating. In addition, we allow the thickness of the thin film silicon to be flexible . The optimal choice of thickness is a trade-off between higher net photon absorption and lower bulk recombination. Our results show that energy conversion of thin film amorphous silicon can be enhanced significantly with appropriate choice of light trapping and taking into consideration the electrical affects.