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We fabricated CZTSSe thin films using optimized SLG-Mo/Zn/Cu/Sn (MZCT) as a stacked structure and described the phenomenon of Zn elemental volatilization using the MZCT stacked structure.

A high-quality Sb₂S₃ thin-absorber with controllable thickness was reproducibly formed by atomic layer deposition (ALD) technique. Compared with conventional chemical bath deposition (CBD), the Sb₂S₃ absorber deposited by ALD did not contain oxide or oxygen impurities and showed a very uniform thickness of Sb₂S₃ absorbers formed on a rough surface of dense blocking TiO₂/F-doped SnOv (bl-TiO₂/FTO) substrate. The planar ALD-Sb₂S₃ solar cells comprised of Au/Poly-3-hexylthiophene/ALD-Sb₂S₃/bl-TiO₂/FTO showed significantly improved power conversion efficiency of 5.77% at 1 sun condition and narrow efficiency deviation, whereas the planar CBD-Sb₂S₃ solar cells exhibited 2.17% power conversion efficiency. The high efficiency and good reproducibility of ALD-Sb₂S₃ solar cell devices is attributed to reduced backward recombination because of the inhibition of oxide defects within ALD-Sb₂S₃ absorber and the conformal deposition of very uniform Sb₂S₃ absorbers on the blocking TiO₂ surface by ALD process.

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Using an appropriate SeS2/Se weight ratio, band gap grading was realized. By increasing the value of VOC through band gap grading in the depletion region, a record VOC deficit of 0.576 V and an efficiency of 12.3% were obtained.

Polyethylene glycol (PEG) has been coupled to many cationic polymers such as polyethylenimine (PEI) to improve the stability and transfection efficiency. We prepared PEG-grafted PEI with different lengths and amounts of PEG and used these graft copolymers as nonviral gene vectors. We measured the complex size and zeta-potential of polymer-DNA complexes in the presence of salt to estimate the stability of polymer-DNA complexes. We also investigated the cytotoxicity and transfection efficiency in C3 cells. In the case of graft copolymers, the stability of polymer-DNA complexes and transfection efficiency were affected by the graft length and amount of PEG side chain. PEG side chains stabilize the polymer-DNA complexes in the presence of salt, but the longer PEG side chains also interrupt the gene delivery in the cells due to the more efficient steric hindrance by longer PEG side chains, and therefore the transfection efficiency is decreased. Short PEG side chains with molecular weight of 350 kDa stabilized the polymer-DNA complexes without decreased transfection efficiency.

For kesterite copper zinc tin sulfide/selenide (CZTSSe) solar cells to enter the market, in addition to efficiency improvements, the technological capability to produce flexible and large-area modules with homogeneous properties is necessary. Here, we report a greater than 10% efficiency for a cell area of approximately 0.5 cm 2 and a greater than 8% efficiency for a cell area larger than 2 cm 2 of certified flexible CZTSSe solar cells. By designing a thin and multi-layered precursor structure, the formation of defects and defect clusters, particularly tin-related donor defects, is controlled, and the open circuit voltage value is enhanced. Using statistical analysis, we verify that the cell-to-cell and within-cell uniformity characteristics are improved. This study reports the highest efficiency so far for flexible CZTSSe solar cells with small and large areas. These results also present methods for improving the efficiency and enlarging the cell area.

Cu2ZnSnS4 (CZTS)‐based materials have a useful band gap and a high absorption coefficient; however, their power conversion efficiency is low compared with that of CdTe and Cu(In,Ga)Se2‐based solar cells. Two of the factors that strongly affect CZTS solar cell characteristics are the MoS2 layer and the presence of defects. In this study, Mo back‐contact layers were annealed to control MoS2 layer formation and the Na content in the Mo layer before the absorber precursor layer was deposited. The increase in oxygen content in the Mo layer suppressed MoS2 layer formation. In addition, the increase in Na diffusion during the initial stage of the absorber precursor deposition decreased the defect density in the absorber layer and in the absorber–buffer interface. These results were verified through measurements of the external quantum efficiency, the temperature dependence of the open‐circuit voltage (VOC), and admittance spectra. The current densities (JSC) and VOC, as well as the power conversion efficiencies, improved as the annealing temperature of the Mo layer increased, which suggests that CZTS solar cell characteristics can be improved by suppressing MoS2 layer formation and increasing Na content in the Mo layer before deposition of the absorber precursor layer. Copyright © 2014 John Wiley & Sons, Ltd.