Optimization of p-i-n GaAs/AlGaAs Heterojunction Nanowire Solar Cell for improved Optical and Electrical Properties

Abstract

In this study, we designed and optimized the performance of pin junction GaAs/AlGaAs heterojunction nanowire solar cell arrays. It is done by performing coupled optoelectronic simulations to find the optimal doping for the GaAs core and AlGaAs shell, and to see the influence of GaAs and AlGaAs shell thickness and junction positions on the solar cell performance. Further, the impact of different surface effects that exists at the semiconductor interface such as surface traps, surface recombination velocities, and associated lifetime degradation are also investigated. It has been observed that a high core and shell doping is essential to achieve the appropriate band configuration and carrier extraction. Further, it is observed that having a larger doping density is more important than having a larger lifetime. The importance of the thickness and the passivation properties of the radial and axial AlGaAs layer is also examined and it has been observed that having a thick AlGaAs shell at the cost of the i-GaAs region can be detrimental to the performance due to increased local carrier generation and recombination. Finally, the effect of having different Aluminium compositions (on the shell) on the photogeneration inside the nanowire is examined and it was observed that having a large Aluminium composition can confine most of the photogeneration to the inner GaAs regions, thus potentially allowing for thicker Aluminium shells which can more efficiently prevent surface recombination.