High-Temperature Polarization-Free III-Nitride Solar Cells with Self-Cooling Effects

Abstract

High-temperature photovoltaics (PV) for terrestrial and extraterrestrial applications have presented demanding challenges for current solar cell materials, such as Si, III−V AlGaInP, and II−VI. Widebandgap III-nitride materials, in contrast, offer several intrinsic advantages that make them extremely appealing for high-temperature applications. In this study, we fabricated and characterized III-nitride solar cells using polarization-free (i.e., nonpolar) InGaN/GaN multiple quantum wells (MQWs). The InGaN solar cells showed a large working temperature range from room temperature (RT) to 450 °C, with positive temperature coefficients up to 350 °C. The peak external quantum efficiencies of the devices showed a 2.5-fold enhancement from RT (∼32%) to 450 °C (∼81%), which is distinct from all other solar cells ever reported. This can be partially attributed to an increase of over 70% in carrier lifetime in nonpolar InGaN MQWs obtained from time-resolved photoluminescence. Furthermore, a thermal radiation analysis revealed a unique self-cooling effect for III-nitride materials, which also helps enhance device performance at high temperature. These results offer new insights and strategies for the design and fabrication of highefficiency high-temperature PV cells.

InGaN/GaN multi‐quantum‐well solar cells under high solar concentration and elevated temperatures for hybrid solar thermal‐photovoltaic power plants

“…However, for the ultra‐high concentration regime, J sc starts to saturate above 573 K, which can be attributed to the observed deterioration of the EQE at high photon energy (Figure 6a) and merits further investigation. Polarization‐free InGaN/GaN MQW solar cells (grown on a nonpolar GaN substrate) have also been observed to exhibit an EQE that increases over the entire spectral range, which results in a superlinear increase of J sc with temperature 15 …”

“…MQWs can be valuable in the subcells comprising MJ PVs because their bandgap can be tailored to near‐optimal values while maintaining lattice‐matching. Equally significant for this study is that the magnitude of the temperature coefficient of cell efficiency can be lessened considerably 14–18 …”

“…III–N alloys are widely used in electronics and optoelectronics industries due to their unique optical and physical properties that include a high absorption coefficient, a wide range of bandgaps (0.64 eV for InN, 3.4 eV for GaN, 6.2 eV for AlN), thermal stability, and radiation resistance 14–16 . Recently, there have been concerted efforts to develop high‐efficiency InGaN solar cells.…”

“…Making the InGaN/GaN layers a few nanometers thick helps avoid grain formation while improving material quality and PV performance 16 . These cells are promising for high‐temperature hybrid solar thermal‐PV power plants and as a power source for near‐sun space missions 14–18 …”

Effect of Nanostructure on Carrier Transport Mechanism of III-Nitride and Kesterite Solar Cells: A Computational Analysis

“…This motivation is driving immense scientific interest to develop highperformance solar cells using In x Ga 1−x N material. Additionally, this alloy has direct band gap with high carrier mobility, drift velocity, high saturation velocity, stable radiation resistance, thermal stability [5], [6] and optical absorption of 10 5 cm 1 , which add more interest to explore further for next generation photovoltaic (PV) applications S Routray, is with the Department of ECE, SRM Institute of Science and Technology, Kattankulathur, Chennai, 603203, India. (e-mail: s.r.routray@ieee.org).…”