Energy band engineering of InGaN/GaN multi-quantum-well solar cells via AlGaN electron- and hole-blocking layers

Abstract

In this paper, we perform a comprehensive study on energy band engineering of InGaN multi-quantum-well (MQW) solar cells using AlGaN electron- and hole-blocking layers. InGaN MQW solar cells with AlGaN layers were grown by metalorganic chemical vapor deposition, and high crystal quality was confirmed by high resolution X-ray diffraction measurements. Time-resolved photoluminescence results showed that the carrier lifetime on the solar cells with AlGaN layers increased by more than 40% compared to that on the reference samples, indicating greatly improved carrier collections. The illuminated current-density (J–V) measurements further confirmed that the short-circuit current density (Jsc) of the solar cells also benefited from the AlGaN layer design and increased 46%. At room temperature, the InGaN solar cells with AlGaN layers showed much higher power conversion efficiency (PCE), by up to two-fold, compared to reference devices. At high temperatures, these solar cells with AlGaN layers also delivered superior photovoltaic (PV) performance such as PCE, Jsc, and fill factor than the reference devices. These results indicate that band engineering with AlGaN layers in the InGaN MQW solar cell structures can effectively enhance the carrier collection process and is a promising design for high efficiency InGaN solar cells for both room temperature and high temperature PV applications.

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

“…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 …”

“…Previous studies on InGaN/GaN MQW solar cells presented temperature‐resolved external quantum efficiency (EQE), temperature‐resolved current density–voltage (I–V) curves under simulated 1‐sun irradiation, and temperature‐resolved photoluminescence, 14 but there have been no reports on their high‐intensity behavior, most notably at high temperature.…”

“…Here, we report experimental measurements on high‐bandgap InGaN/GaN MQW solar cells (an EQE spectral range of 300–460 nm) 14 at solar concentration levels up to 1000 suns and temperatures up to 723 K, each of which is varied independently. Our results demonstrate that efficiency deterioration at elevated temperatures can be avoided and even reversed by using concentrated sunlight.…”