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• Cu 2 Zn 1-x Cd x Sn(S,Se) 4 (CZCTSSe) films were fabricated by a water-based solution method. • Doping Cd in Cu 2 ZnSn(S,Se) 4 (CZTSSe) films could promote its grain growth, improve conductivity and photoconductivity. • Doping of Cd is an effective way to improve short-circuit current and efficiency of CZTSSe solar cell device. Kesterite Cu 2 Zn 1- x Cd x Sn(S,Se) 4 (CZCTSSe) alloy thin films were fabricated by the water-based solution approach. The influence of Cd doping on the morphology, phase structure, element valence states, optical, electrical, and device performance were comprehensively examined. Cd was clearly alloyed into the Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorber layer to form the CZCTSSe compound. By controlling the relative Cd content, band gap values (E g) of the CZCTSSe thin films were engineered between 1.10 eV and 1.21 eV. In addition, doping with Cd led to the enhancement of grain growth as well as improvement of the conductivity and photoelectric property of the absorber layer. In particular, the CZCTSSe (x = 0.4) absorber layer exhibited a pure phase, larger grain size, compact and uniform topography, suitable band gap, Cu-poor and (Cd+Zn)-rich composition, higher conductivity and better photoelectric response. Power conversion efficiency (PCE) is improved from 4.37% of the CZCTSSe (x = 0.0) device to 5.16% of CZCTSSe (x = 0.4) device, and the increases of short-circuit current (J sc) achieved to 8.94 mA/cm2. The encouraging results suggest that doping of Cd is an effective way to improve CZTSSe film properties and promote device efficiency. [ABSTRACT FROM AUTHOR]

Ca 3 Co 4 O 9-δ (Ca349) cathode is prepared by sol-gel method and its performance on new Sm 0.075 Nd 0.075 Ce 0.85 O 2-δ (SNDC) electrolyte was evaluated as cathode for intermediate temperature solid oxide fuel cells (IT-SOFC). The crystal structure and chemical compatibility with SNDC electrolyte are studied by X-ray diffraction (XRD). The micromorphology and electrochemical performance of Ca349 with SNDC electrolyte are characterized. The formation of Ca349 phase and good chemical compatibility between Ca349 and SNDC electrolyte are confirmed by XRD. The Ca349 cathode sintered at 850 °C for 5 h shows the best cathode performance, the area specific resistances (ASR) of Ca349 cathode are found to be 0.236 Ω cm 2 at 800 °C, and the ASR can be further decreased by incorporating SNDC electrolyte. The composite (Ca349-50 wt% SNDC) gives the lowest ASR values (0.093 Ω cm 2 at 800 °C). Its ASR is improved by at least 60% compare to single-phase Ca349 cathode. At 800 °C, the maximal power density of anode-supported SOFCs with Ca349 cathode reaches 410.09 mW cm −2 . The total resistance of the cell was only 0.168 Ω cm 2 . These encouraging data show that Ca349 onto SNDC with good electrochemical performance could be promising as a cathode material of IT-SOFC. [ABSTRACT FROM AUTHOR]

Homogeneous large-grain structure of Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorber has been proven to be one of the conditions for high photoelectric conversion efficiency (PCE) devices. In this work, we explored that the different choices of selenization temperature had influences on the morphology, crystallinity, and electric properties of CZTSSe absorbers. With the selenization temperature of 540°C, the single-layer large-grain structure of CZTSSe absorber could be prepared, and grain boundary defects could be reduced. 540°C is also the transition temperature of the substrate (Soda-lime glass, SLG) of devices. The SLG softens at the transition temperature and the structure is unstable, resulting in Na entering CZTSSe better at 540°C than at a lower selenization temperature. The suitable Na diffusion can promote the growth of grains and help the corresponding device possesses the highest PCE (9.38%), which is also increased by ∼85% than ones prepared under the lower selenization temperature (PCE stayed at 5%). Therefore, the appropriate selenization conditions for the high-efficiency devices also need to consider the properties of the substrates. These conclusions also propose the new point on obtaining the optimal selenization condition for the high-performance CZTSSe devices. • The transition temperature (540°C) of the glass can be the optimal selenization temperature of the CZTSSe absorber. • The optimal Na content of the soda-lime glass can enter CZTSSe absorber under the glass transition temperature. • Under glass transition temperature (540°C), the photoelectric conversion efficiency of CZTSSe device is improved from 5% to 9.38%. [ABSTRACT FROM AUTHOR]

Cation substitutions have the significant impact on suppressing the detrimental defects and associated clusters of CZTSSe thin film solar cells. In our work, trace Ca is used to replace Zn to control the cationic disorder in CZTSSe absorber, improving the performance of CZTSSe solar cells. By tuning the amount of Ca doping, the alloyed Cu 2 Ca x Zn 1- x Sn(S,Se) 4 phase can be formed, and the effects of tiny Ca doping on the properties of CZTSSe absorber are studied in detail. After 2% Ca is doped into the precursor solution, the highest efficiency of CZTSSe solar cells can be optimized to 8.73% from 7.06%, and the improvement of V OC is observed from 382 to 417 mV, which both benefit from the reduced formation of the detrimental defects. Our findings also provide the new insights for further improvement of CZTSSe solar cells based on earth abundant elements. • Substitution of Zn with trace Ca can suppress detrimental defects in absorber for 35 mV increase of devices. • Enhanced crystallinity, grain size, and electrical properties of absorber can be observed after Ca incorporation. • The best efficiency of Cu 2 Ca x Zn 1- x Sn(S,Se) 4 device can be obtained to be 8.73% at x = 0.02. [ABSTRACT FROM AUTHOR]

Layered oxides have been investigated as electrode materials for Na-ion battery owing to its abundant species and easy preparation. Most of the layered oxides are sensitive to water and can't be applied to aqueous Na-ion battery. Layered anode Na 2 [Mn 3 Vac 0.5 ]O 7 with vacancies distributed uniformly in the transition-metal layer is moisture-stable, and the working potential is suitable for aqueous system. However, no effort has been devoted on the development aqueous Na-ion battery based on layered Na 2 [Mn 3 Vac 0.5 ]O 7. Moreover, the cycling and rate performance are poor. In this paper, we first proposed to change the local crystal structure by doping the vacancy with Ti4+ ions. Na 2 [Mn 3 Vac 0.1 Ti 0.4 ]O 7 was screened out with enhanced rate capability and cycling stability. As demonstrated by in-situ X-ray diffraction patterns and electrochemical impedance spectroscopy, the enhanced performance is ascribed to the improved kinetics after Ti doping at the vacancy, which facilitates fast transportation of electron and Na+ ion. Soft X-ray absorption results suggest that Mn4+/Mn3+ redox is involved in the charge transfer during the cycling process. Base on this, aqueous Na-ion cell was successfully fabricated using layered Na 2 [Mn 3 Vac 0.1 Ti 0.4 ]O 7 as anode for the first time, which exhibited excellent rate and cycle performance. [Display omitted] • Layered Na 2 [Mn 3 Vac 0.5- x Ti x ]O 7 is synthesized successfully and studied as anode materials for Na-ion batteries. • The negative electrode exhibits enhanced rate capability and cycling performance. • Kinetics is greatly improved after Ti doping, which facilitates fast transportation of electron and Na+ ions. • Aqueous Na-ion batteries was successfully fabricated with layered oxide, Na 2 [Mn 3 Vac 0.1 Ti 0.4 ]O 7 , as negative electrode material for the first time. • Synthetic atmosphere and carbon content have a great influence on the performance of P-1 type Na 2 [Mn 3 Vac 0.5 ]O 7. [ABSTRACT FROM AUTHOR]

Two-step selenization process has been proved to control Cu 2 ZnSn(S,Se) 4 (CZTSSe) crystallization growth, helping to fabricate a homogeneous large-grain structure of CZTSSe absorber. The two-step selenization process is usually composed of the low-temperature nucleation (LT) and high-temperature grain growth reaction (HT) processes. Here, an exploration of optimizing the annealing conditions at each step in the two-step process is reported to obtain the excellent structure of ionic liquid solution based Cu 2 ZnSn(S,Se) 4 absorber, boosting performance of the solar cell. Based on the basic requirement of an absorber candidate for solar cells (the compact films), three effective kinds of two-step process are confirmed (LT400–10&HT540–10, LT400–10&HT550–10, and LT400–10&HT560–10). We further explore the other properties of sample prepared by one-step and these three kinds of two-step process, respectively, and the optimal two-step process can be identified as LT400–10&HT550–10, which also confirms a homogeneous large-grain structure of CZTSSe absorber. Finally, CZTSSe solar cell with the highest efficiency of 9.24% can be achieved, which can be improved 67% than one by one-step annealing process (5.54%). • The detail optimization of annealing conditions at each step in the two-step selenization process is explored. • Homogeneous large-grain structure of Cu 2 ZnSn(S,Se) 4 absorber can be fabricated at the optimal two-step selenization condition. • The best efficiency of corresponding device can be obtained to be 9.24%, increased by 67% compared with one-step process. [ABSTRACT FROM AUTHOR]