[Paper Review] Efficient and Scalable GaInAs Thermophotovoltaic Devices

Eric J. Tervo, Ryan M. France+16 more|arXiv (Cornell University)|Jul 1, 2022

Thermal Radiation and Cooling Technologies4 citations

TL;DR

This paper presents large-area, scalable single-junction GaInAs thermophotovoltaic (TPV) devices with a record 38.8% efficiency and 3.78 W/cm² power density at 1850°C emitter temperature. The high performance stems from optimized spectral management, high material quality, low series resistance, and a scalable design validated on 2-inch wafers with 12 high-performing devices.

ABSTRACT

Thermophotovoltaics are promising solid-state energy converters for a variety of applications such as grid-scale energy storage, concentrating solar-thermal power, and waste heat recovery. Here, we report the design, fabrication, and testing of large area (0.8 cm$^2$), scalable, single junction 0.74-eV GaInAs thermophotovoltaic devices reaching an efficiency of 38.8$\pm$2.0% and an electrical power density of 3.78 W/cm$^2$ at an emitter temperature of 1850°C. Reaching such a high emitter temperature and power density without sacrificing efficiency is a direct result of combining good spectral management with a highly optimized cell architecture, excellent material quality, and very low series resistance. Importantly, fabrication of 12 high-performing devices on a two-inch wafer is shown to be repeatable, and the cell design can be readily transferred to commercial epitaxy on even larger wafers. Further improvements in efficiency can be obtained by using a multijunction architecture, and early results for a two-junction 0.84-eV GaInPAs / 0.74-eV GaInAs device illustrate this promise.

Motivation & Objective

• To develop high-efficiency, scalable thermophotovoltaic (TPV) devices for practical energy conversion applications.
• To address the challenge of achieving high efficiency at high power density under extreme emitter temperatures (1850°C).
• To enable large-area, repeatable fabrication of GaInAs TPV cells suitable for commercialization.
• To demonstrate the feasibility of scaling single-junction GaInAs TPV devices while maintaining high performance.
• To explore the potential of multijunction architectures for further efficiency gains beyond single-junction limits.

Proposed method

• Design and fabrication of large-area (0.8 cm²) single-junction GaInAs TPV devices lattice-matched to InP substrates.
• Implementation of advanced spectral management to minimize thermal photon losses and maximize photon-to-electron conversion.
• Optimization of device architecture to reduce series resistance and enhance carrier collection efficiency.
• Use of high-quality epitaxial GaInAs material with low defect density to improve voltage and current output.
• Employment of scalable processing techniques on 2-inch wafers to ensure reproducibility and compatibility with industrial production.
• Preliminary testing of a two-junction GaInPAs/GaInAs device to evaluate multijunction potential for higher efficiency.

Experimental results

Research questions

• RQ1 Can single-junction GaInAs TPV devices achieve >38% efficiency at 1850°C emitter temperature while maintaining high power density?
• RQ2 How can spectral management and device architecture be optimized to minimize losses in high-temperature TPV systems?
• RQ3 Is it feasible to fabricate multiple high-performance GaInAs TPV devices on a single 2-inch wafer with consistent performance?
• RQ4 What performance gains can be achieved by transitioning from single-junction to multijunction GaInPAs/GaInAs TPV architectures?
• RQ5 To what extent can the design and fabrication process be scaled for commercial epitaxial production?

Key findings

• The GaInAs TPV device achieved a peak efficiency of 38.8 ± 2.0% at an emitter temperature of 1850°C.
• The device delivered a high electrical power density of 3.78 W/cm² under the same operating conditions.
• Twelve high-performing TPV devices were successfully fabricated on a single 2-inch wafer with consistent performance, demonstrating process repeatability.
• The high efficiency and power density were enabled by a combination of optimized spectral control, low series resistance, and high material quality.
• Early results for a two-junction GaInPAs/GaInAs device show promise for further efficiency improvements beyond the single-junction limit.
• The device architecture and fabrication process are scalable and transferable to larger wafers, supporting commercial viability.