The highly [001]-oriented Sb2Se3 film exhibits an outstanding charge carrier transport efficiency and minimized recombination losses. It delivers a record high saturation hydrogen reduction photocurrent density of −25.4 mA cm−2.

High-quality hole-transport layers (HTLs) with excellent optical and electrical properties play a significant role in achieving high-efficient and stable inverted planar perovskite solar cells (PSCs). In this work, the optoelectronic properties of Cu-doped NiO x (Cu:NiO x ) films and the photovoltaic performance of PSCs with Cu:NiO x HTLs were systematically studied. The Cu-doped NiO x with different doping concentrations was achieved by a high-temperature solid-state reaction, and Cu:NiO x films were prepared by pulsed laser deposition (PLD). Cu+ ion dopants not only occupy the Ni vacancy sites to improve the crystallization quality and increase the hole mobility, but also substitute lattice Ni2+ sites and act as acceptors to enhance the hole concentration. As compared to the undoped NiO x films, the Cu:NiO x films exhibit a higher electrical conductivity with a faster charge transportation and extraction for PSCs. By employing the prepared Cu:NiO x films as HTLs for the PSCs, a high photocurrent density of 23.17 mA/cm2 and a high power conversion efficiency of 20.41% are obtained, which are superior to those with physical vapor deposited NiO x HTLs. Meanwhile, the PSC devices show a negligible hysteresis behavior and a long-term air-stability, even without any encapsulation. The results demonstrate that pulsed laser deposited Cu-doped NiO x film is a promising HTL for realizing high-performance and air-stable PSCs.

Ni vacancy (V Ni ) as an intrinsic defect plays an important role in the optical and electronic properties of NiO x films for inverted planar perovskite solar cell (PSC) applications. This work presents a facile method to fabricate highly dense and continuous NiO x films with excellent optical transmittance and electronic conductivity by pulsed laser deposition. By simply adjusting the preparation parameters, including oxygen partial pressure, postannealing temperature, and duration time, the well-regulated V Ni defects contribute to the modified conductivity and optical transmittance of the NiO x films. The conductivity and optical transmittance of NiO x films are all dramatically enhanced with the increasing oxygen partial pressure. Specifically, the valence band level of NiO x is adjusted by the V Ni defect densities to better match or align with that of the perovskite layer for faster hole extraction with lower energy losses. Density functional theory calculation displays that the Fermi energy level is shifted to a lower energy level due to the enhanced hole carrier concentration generated from the increased V Ni . Benefiting from the excellent optical transmittance, electronic conductivity, and well-matched energy alignment, the inverted PSC with NiO x hole transport layer (HTL) exhibits the highest power conversion efficiency of 16.85% with high open-circuit voltage (1.14 V), short-circuit current density (20.49 mA/cm 2 ), fill factor (0.72), and negligible current−voltage hysteresis effect. This work reveals that modulating the intrinsic defects of NiO x HTLs is an efficient way to achieve high performance of NiO x -based inverted PSCs.

Exploring Sb2Se3 as a photoelectrochemical (PEC) photocathode for water reduction has recently attracted much attention, mainly due to its excellent photophysical properties and perfect band structure matching with water reduction potential. Whereas significant achievements have been made in improving its photocurrent density, the PEC performance remains poor mostly due to the low onset potential or low fill factor. Here, we fabricated S doped Sb2Se3 nanowire arrays with a gradient S concentration (grad-S:Sb2Se3). Gradient S doping creating a cascade valence band structure in Sb2Se3 simultaneously enhances its onset potential and fill factor. Light-trapping effects in nanowire geometry improve the light harvesting efficiency. A further deposition of a thin TiO2 layer is utilized to passivate the detrimental surface defects and form a buried junction with grad-S:Sb2Se3. By employing the prepared grad-S:Sb2Se3 nanowire arrays as the photocathode for water reduction, we achieved a high onset potential of 0.42 V vs RHE, a fill factor of 34%, and a record high half-cell solar-to-hydrogen conversion efficiency of 2% from Sb2Se3-based photocathodes.

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A kinetically controlled growth approach is developed to facilely synthesize preferentially [001]-oriented Sb2Se3 thin-films on diverse substrates.

Photoelectrochemical (PEC) water splitting directly converts solar energy into clean and sustainable hydrogen energy, representing a promising and effective technique for solving the world's energy crisis. A hole transfer layer (HTL) plays a vital role for extracting holes from a semiconductor layer to a back electrode in PEC cells for water splitting. In this work, a TiOx/Sb2Se3/NiOx photocathode was fabricated by using p-NiOx as HTL. We show that the electrical properties of NiOx films can be well adjusted by the pulsed laser deposition technique. By systematically adjusting the electrical properties of the NiOx HTL and passivating the surface defects through coating with the TiOx layer, we achieved a high photocurrent density of up to −18.08 mA cm−2 at 0 V vs a reversible hydrogen electrode (RHE), an onset potential of 0.43 V vs RHE, and a half-cell solar to hydrogen conversion efficiency of 1.01% for the TiOx/Sb2Se3/NiOx photocathode. This work demonstrated NiOx as a potential hole transport material for a cost-effective Sb2Se3 PEC cell.