High performance flexible inverted organic solar cells (OSCs) employing the low temperature cathode buffer bilayer combining the aqueous solution-processed ZnO and polyethylenimine ethoxylated (PEIE) are investigated based on Poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C₆₁-butryric acid methyl ester (P3HT:PC₆₁BM) and Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C₇₁-butyric acid methyl ester (PTB-7:PC₇₁BM) material systems. It is found that, compared with pure ZnO or PEIE cathode buffer layer (CBL), the proper combination of low-temperature processed ZnO and PEIE as the CBL enhanced the short circuit current density (J_SC), resulting in better device performance. The increased J_SC results from the enhanced electron collection ability from the active layer to the cathode. By using the ZnO/PEIE CBL, a power conversion efficiency (PCE) as high as 4.04% for the P3HT:PC₆₁BM flexible device and a PCE as high as 8.12% for the PTB-7:PC₇₁BM flexible device are achieved, which are higher than the control devices with the pure ZnO CBL or pure PEIE CBL. The flexible inverted OSC also shows a superior mechanical property and it can keep 92.9% of its initial performance after 1000 bending cycles with a radius of 0.8 cm. These results suggest that the combination of the low temperature aqueous solution processed ZnO and PEIE can be a promising cathode buffer bilayer for flexible inverted OSCs.

Perovskite solar cell efficiency is not only related with material properties, but also affected by the interface engineering that used in perovskite solar cells. The perovskite film/electrode interface properties play important roles in charge carrier extraction, transport, and recombination. To achieve better interface contact for the device operation, proper interlayers or surface treatment should be applied. In this study, we applied a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) interlayer with a solvent/solution washing treatment as the hole transport layer. It showed that by the solvent/solution treatment, the PEDOT:PSS film conductivity was significantly enhanced, and hence, the charge carrier transfer efficiency was efficiently improved, and the device short-circuit current density was enlarged. Finally, the device efficiency significantly increased from 14.8% to 16.2%.

Perovskite solar cells have gained increasing interest in recent times owing to the rapidly enlarged device efficiency and tunable optoelectronic properties in various applications. In perovskite solar cells, interface engineering plays an important role in determining the final device efficiency and stability. In this study, we adopted TiCl₄ treatment to reduce the surface roughness of the metal oxide layer and improve the perovskite film quality to obtain better device performance. After proper TiCl₄ treatment, the efficiencies of TiCl₄–TiO₂- and TiCl₄–ZnO-based devices were significantly enhanced up to 16.5% and 17.0%, respectively, compared with those based on pristine TiO₂ and ZnO (13.2% and 10.2%, respectively).

Wide-bandgap all-inorganic CsPbIBr2 solar cells with MoOx/Ag/TeO2 composite transparent electrode have been firstly used to construct a 4T perovskite/Si-heterojunction tandem cells. The calculation results showed that the long wavelength transmission (600 to 1100 nm) of MoOx/Ag film can be enhanced remarkably by adding a TeO2 optical capping layer. This resulted in an obviously increase of the PCE (JSC) from 10.70% (17.56 mA/cm2) to 14.76% (24.67 mA/cm2) for corresponding bottom Si cell in CsPbIBr2/Si devices, although the PCE of top CsPbIBr2 cell decreased from 17.52% to 16.58%, the overall PCE of tandem device has increased from 28.22% to 31.34%. This JSC-dependent PCE improvement mainly came from the more balanced light absorption, which can be understood by the optical interference induced light field redistributions in CsPbIBr2/Si devices. Specially, comparing with the original Si cell, the JSC and PCE losses in bottom Si cell have been suppressed to about 33% and 32%, which is superior to most the reported pervoskite/Si tandem cells. Therefore, the tandem of Si cell and CsPbIBr2 cell with optimized MoOx(20 nm)/Ag(8 nm)/TeO2(50 nm) transparent electrode could be the promising cost-effective photovoltaic in the future. This work is instructive to the fabrication of pervoskite/Si tandem solar cells.

Developing an OER electrocatalyst that balances high performance with low cost is crucial for widely adopting PEM water electrolyzers. Ru-based catalysts are gaining attention for their cost-effectiveness and high activity, positioning them as promising alternatives to Ir-based catalysts. However, Ru-based catalysts can be prone to oxidation at high potentials, compromising their durability. In this study, we utilize a simple synthesis method to synthesize a SnO₂, Nb₂O₅, and RuO₂ composite catalyst (SnO₂/Nb₂O₅@RuO₂) with multiple interfaces and abundant oxygen vacancies. The large surface area and numerous active sites of the SnO₂/Nb₂O₅@RuO₂ catalyst lead to outstanding acidic oxygen evolution reaction (OER) performance, achieving current densities of 10, 50, and 200 mA cm⁻² at ultralow overpotentials of 287, 359, and 534 mV, respectively, significantly surpassing commercial IrO₂. Moreover, incorporating Nb₂O₅ into the SnO₂/Nb₂O₅@RuO₂ alters the electronic structure at the interfaces and generates a high density of oxygen vacancies, markedly enhancing durability. Consequently, the membrane electrode composed of SnO₂/Nb₂O₅@RuO₂ and commercial Pt/C demonstrated stable operation in the PEM cell for 25 days at an industrial current density of 1 A cm⁻². This research presents a convenient approach for developing a highly efficient and durable Ru-based electrocatalyst, underscoring its potential for proton exchange membrane water electrolysis.