Device modeling of an optimized monolithic all lattice-matched 3-junction solar cell with efficiency > 50%
Currently, there is a critical need for a photovoltaic design that will convert sunlight into electricity with practical efficiencies higher than 50%. Multijunction Solar Cells (MJSCs) are one of the most promising options to achieve ultra-high efficiencies. III–V compound semiconductors are generally used to fabricate MJSCs; however, limitations imposed by the lattice constants of available substrates strongly restrict which materials can be used for high-quality epitaxial growth. Herein we present an alternative design for an all lattice-matched monolithic 3-junction solar cell formed by (1.93 eV) InAlAs / (1.39 eV) InGaAsP / (0.94 eV) InGaAs, with 5.807 Å lattice constant. 1-dimensional device modeling for each individual subcell, as well as for the tandem device were performed under AM 1.5 direct illumination and concentrated sunlight. The role of concentration in each figure of merit was analyzed and Auger recombination was found to play an important role for high-injection levels. For a current match of 1.58 A/cm^2 we found that > 51% in efficiency can be achieved under 100-suns (with V_(oc)= 3.34 V). A detailed analysis of the effect of concentration on the device performance is presented.