Pulsed Laser Ejection of Single-Crystalline III-V Solar Cells From GaAs Substrates

TL;DR

This paper demonstrates a laser-based method to detach high-quality III-V solar cells from GaAs substrates, enabling efficient reuse and high performance comparable to traditional methods.

Contribution

It introduces a pulsed laser ejection technique for separating crystalline multilayer solar cells from GaAs substrates, offering a potentially scalable and substrate-reusable process.

Findings

Achieved 17.4% efficiency in laser-ejected solar cells.

Demonstrated comparable performance to conventional substrate dissolution methods.

Showed potential for wafer-scale separation per laser pulse.

Abstract

Like many optoelectronics, the highest quality III-V solar cells start out as thin single-crystalline multilayers on GaAs substrates. Separating these device layers from their growth substrate enables higher performing devices and wafer reuse, both of which are critical for III-V solar cell viability in a terrestrial market. Here, we remove rigidly-bonded, lattice-matched, 16 mm$^2$ x 3.5 um thick GaAs devices off a GaAs substrate using a 10 ns, unfocused Nd:YAG laser pulse. The pulse is selectively absorbed in a lower-bandgap, lattice-matched, crystalline layer below the device, driving a quasi-two dimensional ablation event that ejects the crystalline multilayer from the substrate. After minutes of selective wet-chemical etching and front contact deposition, our champion 0.1 cm$^2$ device showed a (17.4 +/- 0.5) % power conversion efficiency and an open-circuit voltage of 1.07 V, using AM1.5 direct (1000 W m$^{-2}$) with no anti-reflection coating. We show that the performance is comparable to similar solar cells produced via conventional substrate dissolution processes. We discuss unique process characteristics and opportunities, such as the potential to separate wafer-sized thin film solar cells per laser pulse.