•Preparation of high-quality perovskite films via ultra-fast spray deposition in air.•The rapid solvent evaporation and nucleation rate is crucial to the formation of film.•The as-fabricated perovskite solar cells exhibited a PCE of 13.54%.Spray deposition has been demonstrated to be a promising method to prepare perovskite thin film with many advantages, such as easy and processable under fully ambient condition, which is suitable for large-scale production. In this work, we reveal two typical spray deposition process of rapid and slow solvent evaporation. It is emphasized that the rapid solvent evaporation process is essential to avoid dendritic crystal and obtain dense perovskite thin film without pin-holes, which can be realized with a suitable substrate temperature. With optimized spray conditions including flow rate of precursor solution and carrier gas pressure, a dense and uniform perovskite layer with full surface coverage was immediately formed in ~5 s without any post-annealing process. The as-fabricated planar heterojunction solar cell achieved a power conversion efficiency (PCE) of 13.54% with 300±30 nm in thickness of perovskite layer. To the best of our knowledge, this result is the highest value for the CH3NH3PbI3 perovskite solar cells fabricated in air condition with high humidity up to 50%.

In this work, quantum dot light-emitting diodes (QD-LEDs) based on a low-temperature solution-processed MoOx hole injection layer were fabricated. As a result of the excellent wettability of the MoOx precursor, a smooth sMoOx HIL film with a roughness of less than 1 nm was obtained. In comparison with a device based on PEDOT:PSS, the best sMoOx-based QD-LED displayed comparable device performance in terms of a maximum luminance of 10 225 cd m−2, a peak current efficiency of 4.04 cd A−1, a maximum external quantum efficiency of 1.61% and, more importantly, an approximately threefold increase in operational lifetime. Furthermore, we investigated the relationship between the thermal treatment of the sMoOx film and the device performance. UPS measurements revealed that the work function of the sMoOx film underwent an upshift from 5.51 to 4.90 eV when the annealing temperature was increased from 50 to 250 °C, which indicated that low-temperature treatment of the sMoOx HIL is beneficial for hole injection and EL performance. This demonstration of a bright, efficient and stable sMoOx-based QD-LED provides another feasible application of solution-processable transition metal oxide materials as the HIL within QD-LEDs and promotes the development of low-cost, all-solution-processed optoelectronic devices.

In this work, all-solution processed, multi-layer yellow quantum dot light emitting diodes (QLEDs), consisting of a hole transport layer of poly(9-vinylcarbazole), emissive layer of CuInS2/ZnS (ZCIS) QDs, and electron transport layer of ZnO nanoparticles, are fabricated. To improve the carrier-balance in QLEDs, a ligand-exchange strategy is employed to replace n-dodecanethiol that caps the surface of CuInS2/ZnS quantum dots with 2-ethylhexanethiol. After this processing, improvement of current efficiency and external quantum efficiency of QLEDs is achieved. The optimized diodes exhibit a maximum luminance of 2354 cd m−2 and an external quantum efficiency of 0.63%, together with a lower turn-on voltage (decreases from 3.1 V to 2.7 V) using these ligand-exchanged QDs as emitting materials. Furthermore, CuInS2-based QLEDs in our study exhibit color retainability with increasing voltage and prolonged use, and show great promise for practical application.

A facile spray deposition method was developed to prepare a high-quality perovskite layer under ambient conditions. However, the performance is expected to be further improved with substrate and the hole transport layer (HTL) optimization and device structure, for instance. MWCNTs with incorporated spiro-OMeTAD exhibited Jsc of 22.13 mA cm−2 and PCE of 10.42%. To infer the origin of the increasing Jsc and PCE, the optical absorption performance, charge transfer and recombination performance were investigated. τ, Rct, Rrec as a function of voltage and EIS measurements revealed the lower transfer resistance and recombination rate in PSCs with MWCNTs compared with the PSCs without MWCNTs. The increased resistance in dark conditions and the dark J–V curves explain the slight changes in the Voc. The SEM images showed that there were no MWCNTs aggregated on the surface of the spiro/MWCNTs composite layer and part of MWCNTs was uncovered by spiro-OMeTAD at the interface of HTM and Au electrode. The decreased ID/IG ratio from 0.90 to 0.68 demonstrated the increased interaction between MWCNTs and spiro-OMeTAD.

Organometal halide perovskites have emerged as promising light absorbers for third-generation photovoltaics. Herein we developed a facile spray deposition process to prepare high-quality perovskite films without any post-annealing under ambient conditions with a high humidity of up to 50%. The as-prepared perovskite films exhibit large grain sizes up to micrometers and full surface coverage. These desirable features significantly enhance the light harvesting efficiency and reduce charge recombination. Furthermore, the morphology and film thickness can be easily controlled by varying the precursor concentration or scanning times during spray deposition. The as-fabricated planar heterojunction solar cells with an optimized perovskite film thickness exhibited a power conversion efficiency of ∼7.89%, which is expected to be further improved with the increase of substrate temperature, the utilization of more compatible substrates, and the optimization of the hole-transport layer and device structure. This simple low-temperature manufacturing process provides a novel strategy for the scalable and fast fabrication of high-quality absorber layers for efficient perovskite based solar cells. The film formation mechanism regarding the nucleation and growth of perovskite films with desirable morphology is also discussed.

Pure phase kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) have been successfully synthesized via a heating-up method utilizing metal salts as cation sources and thioacetamide (TAA) as a coordinating sulphur precursor in combination with oleylamine (OAm) as a coordinating ligand and solvent. The slower release of H2S from the metal–TAA complexes, as compared with the commonly used sulphur powder, is crucial for control of the grain size and size distribution of the NCs. As dominating coordinating ligands, OAm led to Sn-rich nuclei and kesterite CZTS NCs. The formation of pure phase kesterite CZTS NCs depends significantly on the temperature and Zn2+/Sn4+ molar ratio of the reaction system. The formation mechanism of the pure phase kesterite CZTS NCs has been clarified taking into account the chemical potentials of the elements involved.

Hierarchical nanostructures grown directly on transparent conducting oxides hold the promise of overcoming the limitations of current semiconductor-sensitized solar cells based on random networks of nanoparticles. Here, we develop a facile substrate placement angle-dependent hydrothermal process to grow dandelion-like TiO2 nanostructures directly on transparent conductive oxides. TiO2 nanocrystals grown in solution during the synthesis process are found to promote the dandelion-like structure. By using these TiO2 nanostructures as photoanodes, Sb2S3 as the sensitizer, and P3HT as the hole-transporting material, we demonstrate fabrication of all-solid-state semiconductor-sensitized solar cells, which yield solar power conversion efficiency up to 4.71%. Electrochemical impedance spectroscopy indicates that moderate rod fusion at the base beneficially reduces electron recombination in the device. This work provides an innovative method for growing branched, one-dimensional TiO2 nanostructures that can be used for energy harvesting and storage.

One-dimensional TiO2 nanostructures that have large specific surface area have broadened their applications in solar cells and water splitting, but their synthesis still remains a challenge. In this report, vertically ordered rutile TiO2 nanowires with an ultra-high coverage density of 2.4 × 1011 cm−2 and ultra-small width of barely ∼16 nm were synthesized on transparent conducting oxide by a facile solvothermal reaction using methanol and aqueous hydrochloride as solvent. The nanowires were fabricated with Sb2S3 into solid-state solar cells, which yielded a power conversion efficiency of 2.03%. Such a photoanode showed reduced electron recombination, due to moderate wire fusion at the bottom.

Tetragonal CuInS2 (CIS) has been successfully deposited onto mesoporous TiO2 films by in-sequence growth of InxS and CuyS via a successive ionic layer absorption and reaction (SILAR) process and postdeposition annealing in sulfur ambiance. X-ray diffraction and Raman measurements showed that the obtained tetragonal CIS consisted of a chalcopyrite phase and Cu–Au ordering, which related with the antisite defect states. For a fixed Cu–S deposition cycle, an interface layer of β-In2S3 formed at the TiO2/CIS interface with suitable excess deposition of In–S. In the meantime, the content of the Cu–Au ordering phase decreased to a reasonable level. These facts resulted in the retardance of electron recombination in the cells, which is proposed to be dominated by electron transfer from the conduction band of TiO2 to the unoccupied defect states in CIS via exponentially distributed surface states. As a result, a relatively high efficiency of ∼0.92% (Voc = 0.35 V, Jsc = 8.49 mA cm–2, and FF = 0.31) has been obtained. Last, but not least, with an overloading of the sensitizers, a decrease in the interface area between the sensitized TiO2 and electrolytes resulted in deceleration of hole extraction from CIS to the electrolytes, leading to a decrease in the fill factor of the solar cells. It is indicated that the unoccupied states in CIS with energy levels below EF0 of the TiO2 films play an important role in the interface electron recombination at low potentials and has a great influence on the fill factor of the solar cells.Keywords: CuInS2; electron recombination; fabrication; sensitized solar cells; successive ionic layer absorption and reaction (SILAR);

In the present work, the catalyst Pt was evaporated onto the sol–gel WO3, WO3–SiO2 films. These films were annealed at different temperatures and their structures were characterized by infrared, visible near infrared spectroscopy and X-ray diffraction. The coloring kinetics of the films was evaluated. The results revealed that the 0.75WO3–0.25SiO2 composite films had faster coloring rates than the WO3 films. This improved behavior is attributed to the faster diffusion of atomic H resulting from the existence of more absorbed water, more pores, more phase boundaries, and more grain boundaries in the composite films.

In this paper, two electrolytes with water and dimethylformamide as solvents are prepared for the quantum-dot-sensitized solar cells. The impedance spectroscopy method is used to study the influence of the solvents of electrolyte on the performance of quantum-dot-sensitized solar cells. The results show that the cell with dimethylformamide as the solvent exhibits higher charge-transfer resistance between the electrons in TiO2 film and the polysulfide in the electrolyte, leading to longer life time and diffusion length of the electrons. Meanwhile, the dimethylformamide can negatively shift the conduction band edge of TiO2. However, the solubility of the polysulfide in dimethylformamide is too low to meet the requirements of quantum-dot-sensitized solar cells, which results in the lower efficiency of the solar cells based on dimethylformamide compared with that of water.