Light Trapping Optimization in GaAs Thin Film Solar Cell Using Al Nanoparticles

Abstract

This thesis investigates the application of nanoparticles in thin film solar cell (TFSC) for enhancement of light trapping within the solar cell. The absorption of light within TFSC was monitored while nanoparticles of varying size and shape were applied within the absorptive layer of the solar cell. While most research involving solar cell has been primarily ben conducted with Si, some group III-V semiconductors such as GaAs remains a promising candidate specially as a direct band gap material. Thus. GaAs was used as the absorptive semiconductor material and Al nanoparticles were embedded within the cell. Two different textures were applied to the nanoparticle surfaces and the impact on light absorption was observed. An investigation was also made into the effect of applying multiple layers of nanoparticles within the absorptive layer rather than the conventional single layer. Through these efforts, we have demonstrated that application of Al nanoparticles in GaAs TFSC is effective for enhancing light absorption. Compared to the spectral absorption rate (SAR) of 0.0993 the bare solar cell with no nanoparticle, we demonstrated SAR of 0.3207 with the application of nanoparticles with smooth texture. It was observed that 80 nm radius nanoparticles placed at the top of the absorptive layer was optimal. SAR of 0.3267 and 0.3355 was obtained when a rectangular and triangular textures were given to the surface of the nanoparticles. Furthermore, with the application of multiple layers of nanoparticles, the SAR obtained was 0.5780 was obtained. These results clearly demonstrate that application of multiple layers of nanoparticles and also adding texture to those nanoparticles is effective for enhancing light trapping within the solar cell. These works have been done via the use of Comsol Multiphysics software. Different models were created to test the various types of nanoparticle’s impact on the absorption of light and a comparison between the different models has been presented. The simulations were carried out for light of wavelength varying from 400 nm to 1250 nm. This choice of wavelength range is due to the fact that solar radiation in this range is the most intense and thus most relevant for practical application of solar cells. The SAR for all the models were calculated for the mentioned wavelength range and used to compare between the models.