Effect of GaAs nanostructures on silicon based thin film solar cells

Abstract

The limitation of optical absorption due to a shorter optical path and a low absorption coefficient are the main issues concerning the poor performance of silicon-based thin film solar cells. GaAs nanowires can greatly enhance their efficiency by increasing light trapping and decreasing carrier recombination rate. In this work, a detailed study is done to get an improvement of performance of silicon based thin film solar cell by embedding GaAs nanowire on this structure. To analyse the optical and electrical performance of the structures, finite difference time domain analysis and finite element method respectively are considered. It is seen that the conversion efficiency as well as optical absorption gets effected by the change in position, orientation, dimension, period and angle of inclination of nanowires and also the doping concentration of active material. In order to obtain maximum conversion efficiency, all mentioned parameters are optimised. Our proposed structure under AM1.5 G standard solar irradiance achieves a conversion efficiency of 17.25 % with short circuit current density 31.02 mA/cm² and open circuit voltage 0.662 V for a typical 7 µm $\times$ 5 µm surface area and 2 µm thick active layer out of which 17 % is GaAs and 83 % is crystalline silicon. Considering the good degree of structural stability, GaAs nanowires are considered to be grown on silicon active material layer and the interwire gaps are filled with benzo cyclobutene (BCB).