Abstract
We report on the prototyping and development of a highly reflective dielectric back reflector for application in thin-film solar cells. The back reflector is fabricated by Snow Globe Coating (SGC), an innovative, simple, and cheap process to deposit a uniform layer of TiO2particles which shows remarkably high reflectance over a broad spectrum (average reflectance of 99% from 500 nm to 1100 nm). We apply the highly reflective back reflector to tandem thin-film silicon solar cells and compare its performance with conventional ZnO:Al/Ag reflector. By using SGC back reflector, an enhancement of 0.5 mA/cm2in external quantum efficiency of the bottom solar cell and an absolute value of 0.2% enhancement in overall power conversion efficiency are achieved. We also show that the increase in power conversion efficiency is due to the reduction of parasitic absorption at the back contact; that is, the use of the dielectric reflector avoids plasmonic losses at the reference ZnO:Al/Ag back reflector. The Snow Globe Coating process is compatible with other types of solar cells such as crystalline silicon, III–V, and organic photovoltaics. Due to its cost effectiveness, stability, and excellent reflectivity above a wavelength of 400 nm, it has high potential to be applied in industry.
Highlights
Thin-film solar cells are very promising candidates for cost effective and high efficient photovoltaics
We report on the fabrication, prototyping, and implementation of a highly reflective dielectric back reflector prepared by the Snow Globe Coating (SGC) technique which is a simple and cheap method to form a uniform layer of TiO2 particles
In order to demonstrate the superiority of SGC back reflector, we test it on tandem thin-film silicon solar cells and compare its performance with conventional ZnO:Al/Ag back reflectors which have proven their excellent performance in thin-film silicon solar cells [11,12,13]
Summary
Thin-film solar cells are very promising candidates for cost effective and high efficient photovoltaics. Improved reflectivity at the back reflector in tandem thin-film silicon solar cells will allow an increase of the charge carrier generation in the optically thin absorber layers and/or a reduction of the overall thickness of the tandem structure. In this way, the devices will benefit from improved power conversion efficiency and/or decreased deposition time and material, which will reduce the overall production costs per installed kWp. reducing the thickness of the tandem thin-film silicon solar cells will result in better stability of the cells [16]
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