HfO2, Al2O3, and ZnO based Metal-Insulator-Metal photovoltaic structures for solar cell applications

Official URL: http://risc01.sabanciuniv.edu/record=b1817055 (Table of Contents)

Currently, the solar cell market is dominated by silicon-based solar cell since the bandgap of the silicon is an appropriate match to solar spectrum and silicon is most abundant material on the earth. However, the efficiency of the silicon-based solar cells is limited hence the research and development are concentrated on alternative methods. The Metal-Insulator-Metal(MIM) diode consists of an insulator layer sandwiched between two metals. The current generation mechanism is based on the photovoltaic effect that enables to form Metal-Insulator-Metal solar cells. The technological development allows leading investigations about developing highly efficient MIM diode promising broad applications. MIM diodes have several advantages such as low cost, potentially having high conversion efficiency, integrated circuit (IC) compatibility. Therefore, the feasibility of MIM diodes for solar cell application is explored. In the MIM diode, insulator layers are an integral part of the devices, preponderantly determining the performance parameters. MIM diodes with different material selections based on three insulators (HfO2, Al2O3, and ZnO) and three metals (Au, Cr, and Ni) are evaluated to compare performance parameters, with conversion efficiency being prioritized. Based on the responsivities of the devices, the HfO2-based MIM diode gives the highest efficiency under visible light due to the fact that hot electron and leading electrons tunnel through thin energy barrier more asymmetric than the other MIM diodes enabling more number of hot electrons tunneling through. Hence insulating layer is a critical parameter in terms of tunneling probability of hot electrons and optimizing conversion efficiency. At the end of this study, Metal Insulator Metal structure is combined with a converter module that charges a battery that demonstrates the feasibility of MIM solar cell