Improved crystallinity of GaP-based dilute nitride alloys by proton/electron irradiation and rapid thermal annealing

This study presents the positive effects of proton/electron irradiation on the crystallinity of GaP-based dilute nitride alloys. It is found that proton/electron irradiation followed by rapid thermal annealing enhances the PL peak intensity of GaPN alloys, whereas major photovoltaic III-V materials such as GaAs and InGaP degrade their crystal quality by irradiation damage. Atomic force microscopy and transmission electron microscopy reveal no degradation of structural defects. GaAsPN solar cell test devices are then fabricated. Results show that the conversion efficiency increases by proton/electron irradiation, which is mainly caused by an increase in the short-circuit current.

High-Efficiency Ultrathin Si-Based Solar Cells by Cascading Dilute-Nitride GaNAsP

Thin-film solar cells are currently an important research subject. In this study, a lattice-matched GaNAsP/Si tandem cell was designed. We adopted the drift-diffusion model to analyze the power conversion efficiency (PCE) of the solar cell. To find the maximum solar cell PCE, the recombination terms and the interlayer between subcells was omitted. For an optimal tandem cell PCE, this study analyzed the mole fraction combinations of GaNAsP and the thickness combinations between the GaNAsP and the Si subcells of the tandem cell. Our results showed the superiority of the tandem cell over the Si cell. The 4.5 μm tandem cell had a 12.7% PCE, the same as that of the 10.7 μm Si cell. The 11.5 μm tandem cell had 20.2% PCE, while the 11.5 μm Si cell processed 12.7% PCE. We also analyzed the Si subcell thickness ratio of sub-12 μm tandem cells for maximum PCE. The tandem cell with a thickness between 40% to 70% of a Si cell would have a max PCE. The ratio depended on the tandem cell thickness. We conclude that the lattice-matched GaNAsP/Si tandem cell has potential for ultrathin thin Si-based solar cell applications.

Design and Simulation of GaAsN Based Solar Cell with AlGaAs Blocking Layer for Harvesting Visible To Near-Infrared Light

In the present study, the performance parameters of GaAsN dilute nitride-based semiconductor solar cell with and without AlGaAs blocking layers have been investigated in detail by Solar Cell Capacitance Simulator in one dimensional software program (SCAPS-1D). The thickness of absorber, buffer, and blocking layers are varied to achieve the improvement of open circuit voltage, short circuit current, fill factor, efficiency and also to optimize the device structure. The impact of doping and defect densities on the solar cell performance parameters have been analyzed minutely inside the absorber, buffer, and blocking layers. The solar cell thermal stability parameters are also investigated in the temperature region from 273K to 373K. The efficiency of 43.90% and 40.05% are obtained from the proposed solar cells with and without AlGaAs blocking layer, respectively. The present findings may provide insightful approach for fabricating feasible, cost effective, and efficient dilute nitride solar cell.

Study of patterned GaAsSbN nanowires using sigmoidal model

This study presents the first report on patterned nanowires (NWs) of dilute nitride GaAsSbN on p-Si (111) substrates by self-catalyzed plasma-assisted molecular beam epitaxy. Patterned NW array with GaAsSbN of Sb composition of 3% as a stem provided the best yield of vertical NWs. Large bandgap tuning of ~ 75 meV, as ascertained from 4 K photoluminescence (PL), over a pitch length variation of 200–1200 nm has been demonstrated. Pitch-dependent axial and radial growth rates show a logistic sigmoidal growth trend different from those commonly observed in other patterned non-nitride III–V NWs. The sigmoidal fitting provides further insight into the PL spectral shift arising from differences in Sb and N incorporation from pitch induced variation in secondary fluxes. Results indicate that sigmoidal fitting can be a potent tool for designing patterned NW arrays of optimal pitch length for dilute nitrides and other highly mismatched alloys and heterostructures.