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Band gap engineering has been opening a way to enhance the performance of two-dimensional (2D) material devices. Here we report a synthesis of ternary MS 2(1−x) Se 2x (M = Mo, W) alloys with a band gap tunability of ∼170 meV using a solid state reaction method. X-ray photoelectron spectroscopy and Raman scattering characterizations reveal that the change of Se contents can be utilized to tune the composition of the ternary MS 2(1−x) Se 2x (M = Mo, W) alloys. UV–vis–NIR absorption results conform the realization of tunable band gap in MS 2(1−x) Se 2x (M = Mo, W) alloys tailored by different Se contents. The electrical transport investigation of the ternary alloys exhibits an n-type semiconductor behavior demonstrated by back-gated field effect transistors. [ABSTRACT FROM AUTHOR]

Red and brown inorganic pigments Mg 1-x Mn x Fe 2 O 4 (x = 0.0, 0.2, 0.3, 0.4, 0.5) with high far-infrared emissivity and high near-infrared reflectivity were synthesized by the xerogel-microwave method. The pure spinel structure of compounds was confirmed by various methods (X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), and Raman spectroscopy). From the XRD analysis, we can find that a shift in the decreased XRD angle is observed with the addition of the Mn2+ ions because of the radius differences between host ions (Mg2+) and dopant ions (Mn2+) as well as the John-Teller distortion. Furthermore, the results of XRD and Raman spectroscopy demonstrated that Mn dopants can inhibit the grain growth. Meanwhile, the reflective properties were measured by UV–vis–NIR spectrophotometer and the NIR solar reflectance values in the 1400–2500 nm range are over 66% with a maximum 82.9% (x = 0.2). In the experiment where Mn2+ replaced Mg2+ in MgFe 2 O 4 , the band gap decreased from 2.14 eV to 1.86 eV, which results in the decrease of the NIR solar reflectance in 800–1400 nm range. At last, the infrared emissivity of the samples was measured at room temperature, and the average emissivity is over 0.8 with maximum 0.85 (x = 0.5), which is due to the lattice distortion and the intensification of asymmetrical vibration of the Mn–O, Mg–O and Fe–O bonds. • Red and brown inorganic pigments Mg 1-x Mn x Fe 2 O 4 were synthesized by the xerogel-microwave method. • The pigments Mg 1-x Mn x Fe 2 O 4 possess the high far-infrared emissivity and high near-infrared reflectivity. • The pigments Mg 1-x Mn x Fe 2 O 4 could be candidates for "cool pigments". [ABSTRACT FROM AUTHOR]

Up-conversion is a promising technique for harvesting sub-band-gap photons in photovoltaic devices. The implementation and characterization of rare-earth doped up-converters on a-Si:H solar cells are investigated. Three up-conversion phosphors, β-NaYF 4 :Yb 3+ 20%/Er 3+ 1%, β-NaYF 4 :Yb 3+ 25%/Ho 3+ 1% and β-NaYF 4 :Yb 3+ 60%/Tm 3+ 0.5%, are developed and employed as low energy convert materials for a-Si:H solar cells. Two different ways of adhering the up-converter to the a-Si:H solar cell have been implemented: by dissolving the powder in the polydimethylsiloxane (PDMS) and by compressing it into solid slice with a tablet pressing machine. The performance of a-Si:H solar cells integrating the up-converters is investigated under both 980 nm infrared laser diode and simulated solar light source (AM1.5G) illumination. The Current-Voltage measurements reveal that the β-NaYF 4 :Yb 3+ 20%/Er 3+ 1% up-conversion phosphor performs both up-conversion and scattering functions in improving the overall performance of a-Si:H solar cell. [ABSTRACT FROM AUTHOR]