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Current perovskite solar cells (PSCs) often use high-purity single-crystal metal oxides prepared by complex growth processes as electron transport layers (ETLs). In particular, TiO2, as an ETL, can deteriorate the stability of PSCs under illumination. Here, we report a passivation strategy using Er-doped TiO2 synthesized with a one-step hydrothermal method as an ETL. Notably, the oxygen-induced defects in TiO2 have decreased to an acceptable level for PSCs due to the introduction of Er3+ ions. More interestingly, we find that a phase junction can be formed in the mixed crystalline rutile/anatase phase of TiO2, and this TiO2 phase junction can achieve efficient charge separation and accelerate internal electron transfer of the ETL. Taking advantage of these facts, we obtain TiO2-based PSCs through a two-step sequential deposition method in ambient air, whose best efficiency increases by 45.8%. Moreover, the Er-doped device exhibits remarkable ultraviolet resistance ability, whose efficiency is maintained over 90% even after 500 hour ultraviolet irradiation. We believe that this demonstrated strategy provides an effective way for preparing efficient and ultraviolet resistant PSCs in air. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) exhibit remarkable potential for electrochemical reduction of CO 2 to value-added products. However, the commonly pursued methods for preparing SACs are hard to scale up, and sometimes, lack general applicability because of expensive raw materials and complex synthetic procedures. In addition, the fine tuning of coordination environment of SACs remains challenging due to their structural vulnerability. Herein, a simple and universal strategy is developed to fabricate Ni SACs with different nitrogen coordination numbers through one-step pyrolysis of melamine, Ni(NO 3 )∙6H 2 O, and polyvinylpyrrolidone at different temperatures. Experimental measurements and theoretical calculations reveal that the low-coordinate Ni SACs exhibit outstanding CO 2 reduction performance and stability, achieving a Faradic efficiency (FE CO ) of 98.5% at -0.76 V with CO current density of 24.6 mA cm -2 , and maintaining FE CO of over 91.0% at all applied potential windows from -0.56 to -1.16 V, benefiting from its coordinatively unsaturated structure to afford high catalytic activity and low barrier for the formation of *COOH intermediate. No significant performance degradation is observed over 50 h of continuous operation. Additionally, several other metallic single-atom catalysts are successfully prepared by this synthetic method, demonstrating the universality of this strategy., (© 2023 Wiley-VCH GmbH.)

To date, most preparation processes of polycrystalline perovskite films still have to be performed in a glovebox filled with inert gas, limiting the application due to their high cost and complexity. In this work, we exploit a facile processing technique for the preparation of perovskite solar cells (PSCs) under ambient conditions by the Yb 3+ doping effect for SnO 2 electron transfer layer. This remarkable and facile interface doping strategy promotes all-air processed planar PSCs, giving enhanced power conversion efficiency (PCE) from 15.69% to 17.31% with a decreasing hysteresis effect. Moreover, the heating and illumination stability of modified devices by virtue of defect suppression located at electron transfer layer (ETL)/perovskite interface has been effectively improved, retaining over 85% of its initial PCE after 7 h heating at 100 °C in ambient condition and 85% of its initial PCE under 7 h continuous light illumination without any encapsulation. Therefore, it is believed that this Yb-doping strategy for SnO 2 ETL can provide a novel way of promoting the efficiency and stability of devices prepared in the air., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)