Xunan Shen,Chengchun Tang,Chao Zhang,Guanda Li,Yue Zhao,Wei Li,Guifeng Chen,Tie Yang
In current work, Cu2ZnSn(S,Se)4thin films have been prepared by the sol-gel method based on dimethyl sulfoxide solution followed by a modified three-step selenization process. The key process of this method is to divide the Se evaporation and annealing into two different stages: employ a thermal cracking Se source in the Se evaporation stage and an above-atmospheric pressure in the annealing process. The morphological, structural, elemental distributional, and photovoltaic properties of Cu2ZnSn(S,Se)4thin films prepared with the three-step selenization process were systematically investigated. It was found that through this modified selenization process, the formations of secondary phases (ZnSe, CuSnSe3) and a fine-grain bottom layer, which usually exists in the traditional one-step selenization process, were effectively suppressed. These improvements could further reduce the carrier recombination and improve the solar cell performance. The best solar cell is obtained with a short-circuit current density of 28.16 mA/cm2, open-circuit voltage of 404.91 mV, fill factor of 62.91%, and a power conversion efficiency of 7.17% under air mass 1.5 (100 mW/cm2) illumination.Keywords:CZTSSe solar cell;sol-gel method;selenization;thermal cracking Se;above-atmospheric pressure;secondary phases
Tin selenide (SnSe) with an orthorhombic system has recently become a hot spot in the thermoelectric field owing to its low thermal conductivity and high melting point. In this work, P-type SnSe nanoparticles with a mean diameter ca.20–25 nm have been synthesized first by a facile liquid-phase method. Interestingly, the synthesized SnSe nanoparticles have transformed from an intrinsic P-type to an N-type semiconductor after being annealed due to the generation of SnSe 2 secondary phase. The SnSe samples have been characterized by XRD, SEM, XPS, TEM, laser flash, and BET, and the results show that the nanostructure and the presence of SnSe 2 secondary phase enhance phonon scattering effect leading to freshly formed N-type SnSe that has an ultra-low lattice thermal conductivity and a low total thermal conductivity (0.368 Wm −1 K −1 , 0.393 Wm −1 K −1 ) at 723 K. Obviously, this work provides a new way to obtain an N-type SnSe nanomaterial with ultra-low lattice thermal conductivity. Graphical abstract The nano-scale P-type SnSe semiconductor material has been synthesized by a liquid phase method, then has been transformed into an N-type semiconductor after being annealed. The obtained N-type SnSe nanopaticles had an ultra-low lattice thermal conductivity with good stability and repeatability, 0.368 Wm −1 K −1 at 723 K.
Nanoparticles prepared by the coprecipitation method were used as raw materials to fabricate Y3Fe5O12(YIG) ceramics by air pressureless sintering. The synthesized YIG precursor was calcinated at 900–1100 °C for 4 h in air. The influences of the calcination temperature on the phase and morphology of the nanopowders were investigated in detail. The powders calcined at 1000–1100 °C retained the pure YIG phase. YIG ceramics were fabricated by sintering at 1200–1400 °C for 10 h, and its densification behavior was studied. YIG ceramics prepared by air sintering at 1250 °C from powders calcinated at 1000 °C have the highest in-line transmittance in the range of 1000-3000 nm. When the sintering temperature exceeds 1300 °C, the secondary phase appears in the YIG ceramics, which may be due to the loss of oxygen during the high-temperature sintering process, resulting in the conversion of Fe3+into Fe2+.
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