InAlAs photovoltaic cell design for high device efficiency

Abstract

This study presents a new design for a single-junction InAlAs solar cell, which reduces parasitic absorption losses from the low band-gap contact layer while maintaining a functional window layer by integrating a selective etch stop. The etch stop is then removed prior to depositing an anti-reflective coating. The final cell had a 17.9% efficiency under 1-sun AM1.5 with an anti-reflective coating. Minority carrier diffusion lengths were extracted from external quantum efficiency data using physics-based device simulation software yielding 170 nm in the n-type emitter and 4.6 μm in the p-type base, which is more than four times the diffusion length previously reported for a p-type InAlAs base. This report represents significant progress towards a high-performance InAlAs top cell for a triple-junction design lattice-matched to InP.

Electron transport in the solar-relevant InAlAs

“…In particular, the composition lattice matched to InP has been useful as a barrier layer for quantum well high-electron mobility transistors, even for InAs-rich GaInAs strained layers [1][2][3]. But, this material has also been prominent in solar cells, both as the active absorber layer [4][5][6][7][8][9] and as barrier layers in heterojunction cells [10][11][12]. More recently, it has become useful in hot carrier solar cells [13], particularly for cells with materials lattice matched to InAs [14,15].…”

Contactless electroreflectance study of the surface potential barrier in n-type and p-type InAlAs van Hoof structures lattice matched to InP

“…In 1−x Al x As with x = 48% (InAlAs from now on) can be grown lattice-matched to InP, making it a relevant component for many important applications such as telecom lasers [1], InP-based high electron mobility transistors and/or other high frequency devices [2,3]. This alloy is also a natural candidate for claddings, barriers, and waveguides in InPbased quantum cascade lasers [4,5], and has recently been used as an absorber in InP-based multijunction solar cells [6,7]. In addition, InAlAs could be used as a capping layer to protect InP-based heterostructures from oxidation, instead of exploiting other layers such as InGaAs lattice matched to InP (which has a very narrow bandgap) or InP itself, which-for example-is impossible to grow in an MBE system without specialized P sources.…”