We demonstrate InGaN/GaN multiple quantum well solar cells grown by metalorganic chemical vapor deposition on a bulk (0001) substrate with high-performance broadband optical coatings to improve light absorption. A front-side anti-reflective coating and a back-side dichroic mirror were designed to minimize front surface reflections across a broad spectral range and maximize rear surface reflections only in the spectral range absorbed by the InGaN, making the cells suitable for multijunction solar cell integration. Application of optical coatings increased the peak external quantum efficiency by 56% (relative) and conversion efficiency by 37.5% (relative) under 1 sun AM0 equivalent illumination.
As
single-junction Si solar cells approach their practical efficiency
limits, a new pathway is necessary to increase efficiency in order
to realize more cost-effective photovoltaics. Integrating III–V
cells onto Si in a multijunction architecture is a promising approach
that can achieve high efficiency while leveraging the infrastructure
already in place for Si and III–V technology. In this Letter,
we demonstrate a record 15.3%-efficient 1.7 eV GaAsP top cell on GaP/Si,
enabled by recent advances in material quality in conjunction with
an improved device design and a high-performance antireflection coating.
We further present a separate Si bottom cell with a 1.7 eV GaAsP optical
filter to absorb most of the visible light with an efficiency of 6.3%,
showing the feasibility of monolithic III–V/Si tandems with
>20% efficiency. Through spectral efficiency analysis, we compare
our results to previously published GaAsP and Si devices, projecting
tandem GaAsP/Si efficiencies of up to 25.6% based on current state-of-the-art
individual subcells. With the aid of modeling, we further illustrate
a realistic path toward 30% GaAsP/Si tandems for high-efficiency,
monolithically integrated photovoltaics.
The successful development of multijunction photovoltaic devices with four or more subcells has placed additional importance on the design of high-quality broadband antireflection coatings. Antireflective nanostructures have shown promise for reducing reflection loss compared to the best thin-film interference coatings. However, material constraints make nanostructures difficult to integrate without introducing additional absorption or electrical losses. In this work, we compare the performance of various nanostructure configurations with that of an optimized multilayer antireflection coating. Transmission into a four-junction solar cell is computed for each antireflective design, and the corresponding cell efficiency is calculated. We find that the best performance is achieved with a hybrid configuration that combines nanostructures with a multilayer thin-film optical coating. This approach increases transmitted power into the top subcell by 1.3% over an optimal thin-film coating, corresponding to an increase of approximately 0.8% in the modeled cell efficiency.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.