Macro/Microscopic Thermophysics of Optoelectronic Semiconductor Heterostructures

In this work, we systematically characterize the thermophysics of optoelectronic semiconductor hetrostructures, including solar-cell-related structures and light-emitting-diode-related structure. For example, Multi-junction photovoltaic devices are theoretically expected to have a highest limit of efficiency conversion as compared to other designed solar cell heterostructures. Furthermore, as far as the triple-junction InGaP-based photovoltaic solar cells was concerned, changing the indium composition. It was thus well-known that there was an optimum device design for the fixed sun concentration. Indeed, the promise of the multi-junction metamorphic cells providing high conversion efficiency has been realized in the top subcell structures with the indium mole fractions of about 50%. However, according to the increase of the indium composition, the device performance was essentially deteriorated. In this work, we systematically characterized the Debye behaviors of the subcells using photo luminescent spectroscopy. The preparation of triple-junction InGaP-based solar cells composed of top subcell with different InP mole fractions, including 50% and 65%, was carried out by a metal organic vapor phase epitaxy (MOVPE) system. In order to modulate the microstates in response to the change in the nanostructures, the samples investigated were treated by ordering effect and disordering effect device. Considering the statistical redistribution of the microstates in the InGaP-based subcell, the correlation between the photoluminescence (PL) and the continuum theory were investigated as a function of temperature. After examining the luminescent intensity, full-width at half-maximum (FWHM), and thermal activation energy closely, it was found that the In0.5Ga0.5P-based sample revealed better than the In0.65Ga0.35P-based one. According to the Debye continuum model, the Debye temperatures of 430 K and 440 K were obtained for the In0.5Ga0.5P-based sample and the In0.65Ga0.35P-based one by fitting the universal Bloch-Grueneisen curve, respectively. The specific heat contributed by the acoustic phonons were agreement not only with the temperature-dependent line broadenings.

Project ID:PA10308-0436
External Project ID:MOST103-2112-M182-001