Evaluation of Photoconversion Efficiency in InGaN/GaN MQW Solar Cells at High Temperatures

The photoelectric conversion efficiency of InGaN/GaNmultiple quantumwell (MQW) solar cells has been investigated at high temperaturesand the study revealed that their average value decreased from about2.58% at room temperature to about 2.39% at a temperature of 500 & DEG;C.Atomic force microscopy (AFM) analysis indicated that the high-temperaturetreatment made the surface roughness of the material larger, and thecrystal quality deteriorated. X-ray diffraction analysis showed thatthe full width at half-maximum (FWHM) value of the rocking curve andthe degree of relaxation in the InGaN sample increased, indicatingthat the crystal quality in the active region had deteriorated. Photoluminescence(PL) spectroscopic measurements confirmed that the peak intensitydecreased, and a red shift in the peak was observed in the PL spectrum.Moreover, scanning transmission electron microscopy (STEM) revealedan uneven distribution of indium components in the quantum well regionafter high-temperature treatment and that lattice distortion had takenplace. Additionally, first-principles calculations were carried out,which also confirmed that the atomic movement led to a reduction inthe band gap and to the red shift in the peak wavelength. The resultsof this study provided clear evidence that fluctuations of the indiumcomponents took place in the quantum well region under a high-temperaturetreatment at 500 & DEG;C, accompanied by lattice distortion. Thisled to an increase in the number of nonradiative recombination centers,which consequently led to the degradation of the photoelectric conversionefficiency in the fabricated InGaN/GaN MQW solar cells.

Automated summary

The photoelectric conversion efficiency of InGaN/GaN multiple quantum well (MQW) solar cells decreased from 2.58% to 2.39% when the temperature was increased to 500°C. Analysis using atomic force microscopy (AFM) showed increased surface roughness and deterioration of crystal quality due to high-temperature treatment. X-ray diffraction analysis indicated an increase in the full width at half-maximum (FWHM) value and relaxation in the InGaN sample, suggesting degraded crystal quality in the active region. Photoluminescence (PL) spectroscopic measurements confirmed a decrease in peak intensity and a red shift in the peak wavelength in the PL spectrum. Scanning transmission electron microscopy (STEM) revealed uneven distribution of indium components and lattice distortion in the quantum well region after high-temperature treatment. First-principles calculations also confirmed the reduction in band gap and red shift in the peak wavelength due to atomic movement. The fluctuations in indium components and lattice distortion at 500°C led to an increase in nonradiative recombination centers, resulting in the degradation of photoelectric conversion efficiency in InGaN/GaN MQW solar cells.