Enhanced light absorption in GaAs solar cells with internal Bragg reflectors

Abstract

In this work we experimentally investigated the use of epitaxial multilayer dielectric mirrors (Bragg reflectors) as back-surface reflectors in thin-fdm GaAs solar cells on GaAs and silicon substrates.Ab,Ga&/&,,Gq,,,As Bragg reflectors were grown by low-pressure MOCVD on GaAs substrates and shown to exhibit near-ideal optical reflectance and excellent structural perfection. Thin GaAs solar cells grown on Bragg reflectors showed increases in short-circuit current (0.5 to 1 .O mA/cm*) and efficiency (0.7 percentage points) relative to cells without back reflectors. Efficiencies of 24.7% at one sun AM1.5 were measured for GaAs cells only 2 microns thick on Bragg reflectors. In addition to the optical enhancements, Bragg reflectors also appear to improve the defect structure of GaAs-on-Si solar cells. This approach should lead to improved efficiency for GaAs-on-Si solar cells and improved radiation resistance for GaAs cells.

Optical properties of periodic, quasi-periodic, and disordered one-dimensional photonic structures

“…' Solar"cells:'The'role'of'a'photonic'crystal'in'a'photovoltaic'device'is'either'the'localization'or' the'reJinjection'of'the'photons,'that'are'not'absorbed'by'the'active'photovoltaic'material,'back' to'the'device'where'charge'separation'takes'place' [173,174]. 'There'are'several'seminal'works' envisaging'the'employment'of'a'1D'photonic'crystal'to'enhance'the'performance'of'a'solar'cell' [175][176][177][178].' Among' the' most' interesting' achievements' in' the' field,' we' would' like' to' mention' one' of' the' first'demonstrations'of'a'powerJconversion'efficiency'improvement'in'a'dye'sensitized'solar' cell' (DSSC)' with' a' 1D' porous' photonic' crystal' [179],' the' fabrication' of' a' transparent' 1D' photonic' crystal' based' DSSC' [180],' the' integration' of' a' porous' photonic' crystal' in' a' organometal' halide' perovskite' solar' cell' [181],' the' integration' of' 1D' photonic' crystal' in' a' semitransparent'polymer'solar'cell' [182,183] 4.1.…”

Design of an intermediate Bragg reflector within triple-junction solar cells for spectrum splitting applications

“…The first application of a DBR integrated into a solar cell was by Tobin et al in 1991 for GaAs cells [10]. Fifteen periods of an Al0.1Ga0.9As/Al0.85Ga0.15As bilayer were deposited on the substrate prior to the active layers, leading to a 0.5-1.0 mA/cm 2 enhancement in shortcircuit current Jsc and 0.7% absolute gain in efficiency.…”

“…Fifteen periods of an Al0.1Ga0.9As/Al0.85Ga0.15As bilayer were deposited on the substrate prior to the active layers, leading to a 0.5-1.0 mA/cm 2 enhancement in shortcircuit current Jsc and 0.7% absolute gain in efficiency. In addition, a DBR in GaAs-on-Si tandem cells showed the potential benefit of reducing threading dislocation densities [10].…”

Thin silicon solar cells with SiОх /SiNx Bragg mirror rear surface reflector

“…This effect is even more crucial for thin SC. One of the ways to diminish these losses is to increase the optical path for weakly absorbed photons within the SC [3]. Bragg mirrors (BM) as rear surface reflectors could provide the conditions for multi-passing of IR photons within the SC.…”