Epitaxial lift‐off (ELO) InGaP/GaAs/InGaAs inverted metamorphic triple‐junction solar cells are encapsulated with a micro/nanostructured polydimethylsiloxane (PDMS) film. The microprism array (MPA) is realized on the PDMS film to redirect the light incident on the metal grid line to the active area. Subwavelength structures (SWSs) are also introduced onto the PDMS film to suppress the Fresnel optical reflection loss. Triangular and hemicylindrical shapes are considered for the MPA. The optical responses of the two MPAs are calculated by using ray‐tracing methods. The triangular MPA performs better than the hemicylindrical MPA in terms of light‐redirection efficiency. It is confirmed that 82.0% of the light incident on the metal grid can be harvested by the effect of the triangular MPA and the Fresnel optical reflection loss is reduced effectively by the SWSs. These effects contribute to photocurrent enhancement. The short‐circuit current density and power conversion efficiency of the flexible ELO triple‐junction solar cells integrated with the micro/nanostructured PDMS film improve by 7.0% and 7.1%, respectively, compared with those of the solar cells without the PDMS film. By using the flexible PDMS film for light management, the flexibility of the ELO solar cells is preserved.

The surface morphology of a buffer template is an important factor in the heteroepitaxial integration of optoelectronic devices with a significant lattice mismatch. In this work, InP-based long-wave infrared (~8 µm) emitting quantum cascade lasers with active region designs lattice-matched to InP were grown on GaAs and Si substrates employing InAlGaAs step-graded metamorphic buffer layers, as a means to assess the impact of surface roughness on device performance. A room-temperature pulsed-operation lasing with a relatively good device performance was obtained on a Si template, even with a large RMS roughness of 17.1 nm over 100 µm2. Such results demonstrate that intersubband-operating devices are highly tolerant to large RMS surface roughness, even in the presence of a high residual dislocation density.

AbstractThis research introduces a pioneering approach to solar water splitting technology, utilizing an innovative, highly efficient immersed system. The system incorporates a flexible array of electrochemical and photoelectrochemical cells, powered by high‐performance III‐V triple‐junction cells. Remarkably, this method significantly boosts the solar‐to‐hydrogen (STH) conversion efficiency, reaching a record 20.7% under 1 sun illumination, employing earth‐abundant catalysts operating at ambient temperature. These findings highlight extensive scope for further optimization, including minimizing optical transmission losses, mitigating shading effects, and reducing the overpotential of the electrochemical cells, thereby augmenting the STH efficiency to an estimated 28%. Through a comprehensive techno‐economic analysis, a levelized cost of hydrogen (LCOH) of 8.3 USD kg−1 is estimated, forecasting the potential for a reduction to a competitive 1.8 USD kg−1 with improved efficiency, increased capacity factors, and decreased production costs. A sensitivity analysis emphasizes the significant influence of factors such as III‐V cell cost, electrolyzer membrane cost and capacity factor on the LCOH. Overall, this study signifies crucial progress toward a highly efficient and economically viable solar water splitting solution, promising a sustainable route for hydrogen production.

This study presents the growth and characterization of an 8.1 μm-emitting, InGaAs/AlInAs/InP-based quantum cascade laser (QCL) formed on an InP-on-Si composite template by metalorganic chemical vapor deposition (MOCVD). First, for the composite-template formation, a GaAs buffer layer was grown by solid-source molecular-beam epitaxy on a commercial (001) GaP/Si substrate, thus forming a GaAs/GaP/Si template. Next, an InP metamorphic buffer layer (MBL) structure was grown atop the GaAs/GaP/Si template by MOCVD, followed by the MOCVD growth of the full QCL structure. The top-surface morphology of the GaAs/GaP/Si template before and after the InP MBL growth was assessed via atomic force microscopy, over a 100 μm2 area, and no antiphase domains were found. The average threading dislocation density (TDD) for the GaAs/GaP/Si template was found to be ∼1 × 109 cm−2, with a slightly lower defect density of ∼7.9 × 108 cm−2 after the InP MBL growth. The lasing performance of the QCL structure grown on Si was compared to that of its counterpart grown on InP native substrate and found to be quite similar. That is, the threshold-current density of the QCL on Si, for deep-etched ridge-guide devices with uncoated facets, is somewhat lower than that for its counterpart on native InP substrate, 1.50 vs 1.92 kA/cm2, while the maximum output power per facet is 1.64 vs 1.47 W. These results further demonstrate the resilience of QCLs to relatively high residual TDD values.