Modeling, design and experimental results for high efficiency multi-junction solar cells lattice matched to InP

Abstract

The high conversion efficiencies demonstrated by multi-junction solar cells over the past three decades have made them indispensable for use in space and are very attractive for terrestrial concentrator applications. The multi-junction technology consistently displays efficiency values in excess of 30%, with record highs of 37.8% under 1 sun conditions and over 44% under concentration. However, as material quality in current III-V multi-junction technology reaches practical limits, more sophisticated structures will be required to further improve on these efficiency values. In a collaborative effort amongst several institutions we have developed a novel multi-junction solar cell design that has the potential to reach the 50% conversion efficiency value. Our design consists of a three junction cell grown on InP substrates which achieves the optimal bandgaps for solar energy conversion using lattice matched materials. In this work, we present the progress in the different subcells comprising this multi-junction structure. For the top cell, InAlAsSb quaternary material is studied. For the middle, InGaAlAs and InGaAsP materials and devices are considered and for the bottom, a multi-quantum well structure lattice matched to InP for fine bandgap tunability for placement in an InGaAs cell is demonstrated.

Characterization of InAlAs solar cells grown by MOVPE

“…As such, lnAlAs is being investigated for its potential as the top cell in a variety of newly proposed lattice matched triple-junction PV designs, suited for InP substrates or even alternative lattice constants [2][3][4][5]. Furthermore, research on the ternary InAIAs forms the basis for exploration of other alloys, such as lnAlAsSb.…”

Imaging Atomic-Scale Clustering in III–V Semiconductor Alloys

“…However, direct bandgaps spanning the range of 1.45–1.81 eV have been predicted using interpolation methods . Simulations show that multijunction photovoltaic devices, with the potential to reach 50% conversion efficiency, could be developed using the extensive design space of quaternary alloys lattice matched to InP. − In practice, the growth of InAlAsSb is challenging because it is known to suffer from a miscibility gap . Phase segregation has previously been indicated in InAlAsSb by photoluminescence (PL) spectroscopy, including anomalously low PL emission with an S-shaped temperature dependence .…”