ENHANCEMENT OF ABSORPTION CHARACTERISTICS OF MULTINANOLAYER PHOTOVOLTAIC CELLS BY USING CHIRPED DISTRIBUTED BRAGG REFLECTORS

Abstract

An electromagnetic wavelength-scale analysis of optical characteristics of multinanolayer photovoltaic (PV) cells based on a Si p-i-n type absorber is performed. A broadband non- periodic (chirped) distributed Bragg reflector (DBR) located on the top of the PV structure is supported by a metallic layer (Cu) and SiO₂ substrate. The numerical analysis is performed by the method of single expression (MSE). MSE is a non-traditional method of boundary problem solution in classical electrodynamics, and a convenient tool for wavelength-scale analysis of any multilayer and modulated photonic structure. Absorbing, reflecting and transmitting char- acteristics of multinanolayer PV cells with chirped DBR mirrors are obtained via performed computer modelling by the MSE. The influence of the number, thicknesses and alternation of the layers of the chirped DBRs on the absorbing characteristics of multinanolayer PV cells is analysed to determine favourable configurations for enhancement of their absorption effi- ciency. The localization of the electric component of the optical field and the power flow dis- tribution within the considered PV structures are obtained to confirm an enhancement of ab- sorption efficiency in favourable configurations of multinanolayer PV cells. The results of the performed electromagnetic wavelength-scale analysis will have a scientific and practical im- portance for optimizing the operation of thin-film multinanolayer PV cells with broadband resonant reflectors on the subject of enhancement of their efficiency.