Optimization of Cuprous Oxide (Cu2O) Heterojunction Solar Cells Using Silvaco TCAD

Abstract

Cuprous oxide (Cu2O) based solar cells are modern thin film solar cells usually created as heterojunctions such as n-ZnO/p-Cu2O as in our study, and have attracted more attention of researchers for low-cost photovoltaic applications, because they are abundant, non-toxic and relatively stable. The objective of the present work was to improve the performances of heterojunction solar cell AZO/n-ZnO/p-Cu2O by changing several parameters using Silvaco Atlas software, which is a simulation software that calculates the electrical output parameters of the studied solar cell. The idea was about changing thickness, doping concentration of layers and inserting a highly doped layer as a passivation layer in order to improve the solar cell performance. One of the benefits of this work is the exploitation of the results obtained through the optimization by simulation without material loss and time, i.e. as an application to our work. The thesis was organized in three chapters. The first one was dedicated to the principles of solar cells which presented in details. In the second one, describes solar cells on the basis of cuprous oxide absorber layer (Cu2O), and their structure, optical and electrical properties, their methods of manufacturing, definition of ZnO as a solar cell material, effect of some parameters on ZnO/Cu2O heterojunction solar cell characteristics, finally, literature review of the Cu2O based heterojunction solar cells. While in the third chapter, the most important elements were presented in this work, starting with general concepts about Silvaco TCAD software with the simulation steps of the studied device, description of simulated structure of heterojunction solar cell based on Cuprous oxide (Cu2O) with the model adopted in our study, finally, all the results were presented in the form of curves and tables with their discussions, where the optimum parameters obtained in this work are: First, at thickness of the ZnO layer of 0.041μm, conversion efficiency was determined of 4.253%, showing that their effects are most likely negligible, because it as a window layer. At Cu2O thickness of 6.6μm, we obtained a conversion efficiency of 4.646%, showing significant effect, because it is an absorbent layer. At doping concentration of the ZnO layer of 3×1020𝒄𝒎−𝟑, conversion efficiency was determined of 4.823%, and at doping concentration of Cu2O layer of 6×1015𝒄𝒎−𝟑, we obtained a conversion efficiency of 5.015%. Thus, these changes have clear effects on the conversion efficiency of solar cell. While, the presence of the heavily doped layer does not strongly effect on output parameters, where: At its doping concentration and thickness at 4×1020𝒄𝒎−𝟑, and 0.6μm, we found η = 5.017% and 5.017%, respectively. In conclusion, we are confident that the Cuprous oxide (Cu2O) heterojunction solar cells have the ability to achieve high efficiency because they have high theoretical efficiency. The data collected in this effort raises many questions for future research. The data reveals many interesting electronic and optical properties of Cuprous oxide. Efforts could be made to better understand thus, improve better. Where we can offer further enhancements. For example, we can change band gap (Eg) and investigate its effect, because Cu2O has a non-fixed band gap value. Also, we can insert others types of passivation such as chemical passivation and passivation of a metal contact with a tunneling layer; to reduce the recombination surface