Single-atom catalysts anchoring offers a desirable pathway for efficiency maximization and cost-saving for photocatalytic hydrogen evolution. However, the single-atoms loading amount is always within 0.5% in most of the reported due to the agglomeration at higher loading concentrations. In this work, the highly dispersed and large loading amount (>1 wt%) of copper single-atoms were achieved on TiO2, exhibiting the H2 evolution rate of 101.7 mmol g−1 h−1 under simulated solar light irradiation, which is higher than other photocatalysts reported, in addition to the excellent stability as proved after storing 380 days. More importantly, it exhibits an apparent quantum efficiency of 56% at 365 nm, a significant breakthrough in this field. The highly dispersed and large amount of Cu single-atoms incorporation on TiO2 enables the efficient electron transfer via Cu2+-Cu+ process. The present approach paves the way to design advanced materials for remarkable photocatalytic activity and durability.

Printable triple mesoscopic structures for organic–inorganic hybrid perovskite solar cells (PSCs) have recently obtained significant attention, and they possess a superior long-term stability in comparison to those of planar structured PSCs. In comparison with planar structures, however, triple mesoscopic structures typically show lower open-circuit voltages (V oc). Evidence suggests that nonradiative recombination governed by the mismatched energy levels between the perovskite film and the electron-transporting layer (or hole-transporting layer) is the main cause for photovoltage losses. Here we introduced a gradient bilayered zinc tin oxide (ZTO) ETL for fully printed mesoporous PSCs. This approach reduces the energy loss and augments the V oc, which benefits from the suitable matching of cascade level between the perovskite and the ZTO ETL. By tuning of the Zn content, ZTO films with gradient energy levels and different carrier concentrations are acquired. Our optimized device delivers a high V oc of 1.02 V and PCE of 15.86%. These findings provide a simple pathway to design the interface between ETL and perovskite and to tailor the band alignment to suppress interfacial trap-assisted recombination of fully printed mesoporous PSCs for enhancing V oc and charge extraction simultaneously.

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Fully printable, hole-conductor-free, carbon-based perovskite solar cells are attractive and promising for industrial production due to their low cost and high stability. However, the efficiency of this type of device is difficult to improve due to the undesirable interfacial contact during the printing process compared to the spin coating process and the higher recombination ratio than the devices with a hole conductor. Herein, a porous anatase nanocrystal (Nano-TiO2) derived by MIL-125, a type of titanium-based metal–organic frameworks (MOFs), was used as the electron transporting material (ETM). The Nano-TiO2 can be conveniently covered on a substrate by screen-printing and still maintain the cakelike morphology, which is beneficial to large-scale production. Moreover, the cakelike morphology composed of nanocrystals is more favorable for the crystallization of perovskites than commercial TiO2 (P25) and can reduce the recombination of photogenerated electron–hole pairs to improve device performance. The device based on Nano-TiO2 shows a V OC of 0.907 V and a fill factor of 68.14% at the forward scan, which is higher than that of the devices based on P25 (0.853 V and 52.95%). It paves a promising way for carbon-based printable perovskite solar cells.