Preparation and Simulation of AlGaN/CdS/Si Double Heterojunction for Solar Cell Application

Abstract

This study presents a simple pulsed laser deposition technique (PLD) for the preparation of aluminium gallium nitride (AlGaN) thin film on CdS/Si substrate for solar cell application. A CdS layer was deposited on Si using thermal evaporator system and then AlGaN was grown on CdS/Si using the PLD technique using AlN and GaN targets. The effect of varying the number of laser pulses (300 and 600) and GaN/AlN ratio on structural, optical and morphological properties of the AlGaN thin film was investigated. Structural characterizations by x-ray diffraction revealed (0002) plane of AlGaN along with the diffraction peaks of GaN and AlN. The crystallite size of the AlGaN was decreased by increasing the GaN/AlN ratio. Photoluminescence (PL) spectra revealed that the energy band gap of AlGaN was slightly varied between 3.6 eV and 3.7 eV due to change of the GaN/AlN ratio. Surface roughness of the AlGaN was increased on increasing then laser pulses from 300 to 600 at lower GaN/AlN ratio, while it showed opposite trend in the case in which relatively higher ratio was used. Field-emission scanning electron microscopy showed semi-spherical grains of the films whose size was changed by changing the number of laser pulses and also the GaN/AlN ratio. The results of solar cell efficiency indicated a low efficiency (0.27%) of CdS/Si based solar cell which was significantly improved due to the growth of AlGaN on CdS/Si. solar cells based on AlGaN/CdS/Si prepared under various were found to be 2.50%, 2.83%, 2.23% and 2.81%. The solar cell efficiency obtained from the simulation study (2.68%, 2.50%, 3.29% and 3.25%) was in good agreement with the experimental results.