Highly efficient copper-zinc-tin-selenide (Cu2ZnSnSe4 ; CZTSe) thin-film solar cells are prepared via the electrodepostion technique. A metallic alloy precursor (CZT) film with a Cu-poor, Zn-rich composition is directly deposited from a single aqueous bath under a constant current, and the precursor film is converted to CZTSe by annealing under a Se atmosphere at temperatures ranging from 400 °C to 600 °C. The crystallization of CZTSe starts at 400 °C and is completed at 500 °C, while crystal growth continues at higher temperatures. Owing to compromises between enhanced crystallinity and poor physical properties, CZTSe thin films annealed at 550 °C exhibit the best and most-stable device performances, reaching up to 8.0 % active efficiency; among the highest efficiencies for CZTSe thin-film solar cells prepared by electrodeposition. Further analysis of the electronic properties and a comparison with another state-of-the-art device prepared from a hydrazine-based solution, suggests that the conversion efficiency can be further improved by optimizing parameters such as film thickness, antireflection coating, MoSe2 formation, and p-n junction properties.

We report a new ternary Zn 2 SnO 4 (ZSO) electron-transporting electrode of a CH 3 NH 3 PbI 3 perovskite solar cell as an alternative to the conventional TiO 2 electrode. The ZSO-based perovskite solar cells have been prepared following a conventional procedure known as a sequential (or two-step) process with ZSO compact/mesoscopic layers instead of the conventional TiO 2 counterparts, and their solar cell properties have been investigated as a function of the thickness of either the ZSO compact layer or the ZSO mesoscopic layer. The presence of the ZSO compact layer has a negligible influence on the transmittance of the incident light regardless of its thickness, whereas the thickest compact layer blocks the back-electron transfer most efficiently. The open-circuit voltage and fill factor increase with the increasing thickness of the mesoscopic ZSO layer, whereas the short-circuit current density decreases with the increasing thickness except for the thinnest one (∼100 nm). As a result, the device with a 300 nmthick mesoscopic ZSO layer shows the highest conversion efficiency of 7%. In addition, time-resolved and frequency-resolved measurements reveal that the ZSO-based perovskite solar cell exhibits faster electron transport (∼10 times) and superior charge-collection capability compared to the TiO 2 -based counterpart with similar thickness and conversion efficiency.

Among ternary oxides, Zn2 SnO4 (ZSO) is considered for dye-sensitized solar cells (DSSCs) because of its wide bandgap, high optical transmittance, and high electrical conductivity. However, ZSO-based DSSCs have a poor performance record owing largely to the absence of systematic efforts to enhance their performance. Herein, general strategies are proposed to improve the performance of ZSO-based DSSCs involving interfacial engineering/modification of the photoanode. A conformal ZSO thin film (blocking layer) deposited at the fluorine-doped tin oxide-electrolyte interface by pulsed laser deposition suppressed the back-electron transfer effectively while maintaining a high optical transmittance, which resulted in a 22 % improvement in the short-circuit photocurrent density. Surface modification of ZSO nanoparticles (NPs) resulted in an ultrathin ZnO shell layer, a 9 % improvement in the open-circuit voltage, and a 4 % improvement in the fill factor because of the reduced electron recombination at the ZSO NPs-electrolyte interface. The ZSO-based DSSCs exhibited a faster charge injection and electron transport than their TiO2 -based counterparts, and their superior properties were not inhibited by the ZnO shell layer, which indicates their feasibility for highly efficient DSSCs. Each interfacial engineering strategy could be applied to the ZSO-based DSSC independently to lead to an improved conversion efficiency of 6 %, a very high conversion efficiency for a non-TiO2 based DSSC.