Most practical applications of photocatalysts will involve coatings on an inert support; here we have examined how copper doping of spin coated porous TiO2 films affects their physical ...characteristics and photocatalytic activity. The photocatalytic degradation of stearic acid was used as a measure of photocatalytic activity for catalysts spin coated from a sol-gel onto glass with 0, 0.1, 0.5, 1, 2.5 and 5 wt% copper introduced into the catalyst lattice before gelation. The effects of spin coating speed on film thickness, structure and band gap were studied and the nature of the copper incorporated into the films examined with XPS and XANES measurements. Increased spin coating speeds reduces the thickness of the deposited films from ∼ 50 μm to ∼ 20 μm until a spin speed of ∼ 3000 rpm at which point non-Newtonian behaviour of the gels prevents further reductions in film thickness. A larger effect on film thickness is the presence of the added copper nitrate which results in thinner films. After calcining, XANES shows the bulk of the copper to be in a Cu(II) state but at the surface of the thinnest, most active films XPS shows only Cu(I). Photocatalytic activity is much more strongly affected by the presence of the copper than the thickness of the films with 0.1 wt% Cu catalysts as much as 10 times more active than the undoped catalysts. Increasing the copper content, however, reduces activity until at ∼ 5 wt% activity is lower than for the pure TiO2 films.
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•Polymer templating creates mesoporous TiO2 films as effective photocatalysts.•Contaminant does not penetrate below the surface of the porous catalyst.•Added porosity does not give contaminant more access to catalyst surface.•Low wt% Cu dramatically increases the photocatalytic activity due to Cu(I) ions.•Film thickness not a significant contributor to the photocatalytic activity.
High‐performance organic solar cells (OSCs) at the current stage are majorly accomplished from the processing of halogenated solvents, such as chloroform, which will be constrained for upscale ...fabrication due to the adverse health and environmental impacts. Therefore, exploring the high‐performance OSCs from non‐halogenated solvent processing becomes highly necessary, yet largely lagged behind. Herein, it is demonstrated high‐performance OSCs can be obtained from the hot spin processing of different non‐halogenated solvents, and achieve the highest reported efficiency of OSCs from non‐halogenated solvent processing so far. It is revealed that the phase evolution of ternary blends during solution‐to‐solid transition has a correlation to the substrate temperature. With the elevated substrate temperature of hot spin coating, the optimal blend films can be secured in different kinds of non‐halogenated solvents. As result, high‐performance OSCs are obtained with excellent power conversion efficiencies of 18.25% in o‐xylene, 18.20% in p‐xylene, and 18.12% in toluene, respectively. To the author's best knowledge, these results represent the best‐performed OSCs made from non‐halogenated solvents so far.
High‐performance organic solar cells (OSCs) are feasibly obtained from the hot spin coating of different kinds of non‐halogenated solvents. It is revealed that the blend phase evolution during solution‐to‐solid transition has a correlation to the substrate temperature. As result, high‐performance OSCs are obtained with power conversion efficiencies of 18.25% in o‐xylene, 18.20% in p‐xylene, and 18.12% in toluene, respectively.
The optoelectronic properties, morphology, and consequently the performance of metal halide perovskite solar cells are directly related to the crystalline phases and intermediates formed during film ...preparation. The gas quenching method is compatible with large‐area deposition, but an understanding of how this method influences these properties and performance is scarce in the literature. Here, in situ grazing incidence wide angle X‐ray scattering is employed during spin coating deposition to gain insights on the formation of MAPbI3 and CsxFA1−xPb(I0.83Br0.17)3 perovskites, comparing the use of dimethyl sulfoxide (DMSO) and 2‐methyl‐n‐pyrrolidone (NMP) as coordinative solvents. Intermediates formed using DMSO depend on the perovskite composition (e.g., Cs content), while for NMP the same intermediate PbI2(NMP) is formed independently on the composition. For MAPbI3 and CsxFA1−xPb(I0.83Br0.17)3 with a small amount of Cs (10% and 20%), the best efficiencies are achieved using NMP, while the use of DMSO is preferred for higher (30% and 40%) amount of Cs. The inhibition of the 2H/4H hexagonal phase when using NMP is crucial for the final performance. These findings provide a deep understanding about the formation mechanism in multication perovskites and assist the community to choose the best solvent for the desired perovskite composition aiming to perovskite‐on‐silicon tandem solar cells.
In situ grazing incidence wide angle X‐ray scattering during spin coating preparation of hybrid‐organic lead halide perovskite using gas quenching reveals that the intermediates formed using dimethyl sulfoxide depends on the composition. Otherwise, for 2‐methyl‐n‐pyrrolidone, a unique intermediate is formed. Such a formation mechanism has an impact on the device performance.
The vast majority of ternary organic solar cells are obtained by simply fabricating bulk heterojunction (BHJ) active layers. Due to the inappropriate distribution of donors and acceptors in the ...vertical direction, a new method by fabricating pseudoplanar heterojunction (PPHJ) ternary organic solar cells is proposed to better modulate the morphology of active layer. The pseudoplanar heterojunction ternary organic solar cells (P‐ternary) are fabricated by a sequential solution treatment technique, in which the donor and acceptor mixture blends are sequentially spin‐coated. As a consequence, a higher power conversion efficiency (PCE) of 14.2% is achieved with a Voc of 0.79 V, Jsc of 25.6 mA cm−2, and fill factor (FF) of 69.8% compared with the ternary BHJ system of 13.8%. At the same time, the alloyed acceptor is likely formed between two the acceptors through a series of in‐depth explorations. This work suggests that nonfullerene alloyed acceptor may have great potential to realize effective P‐ternary organic solar cells.
The vast majority of ternary organic solar cells are obtained by simply fabricating bulk heterojunction active layers. Herein, a new method by fabricating pseudoplanar heterojunction ternary organic solar cells is proposed. At the same time, the alloyed acceptor is likely formed between two nonfullerene acceptors, which may be more suitable for facilitating pseudoplanar heterojunctions.
Vertically oriented highly crystalline 2D layered (BA)2(MA)n−1PbnI3n+1 (BA = CH3(CH2)3NH3, MA = CH3NH3, n = 3, 4) perovskite thin‐films are fabricated with the aid of ammonium thiocyanate (NH4SCN) ...additive through one‐step spin‐coating process. The humidity‐stability of the film is certified by the almost unchanged X‐ray diffraction patterns after exposed to humid atmosphere (Hr = 55 ± 5%) for 40 d. The photovoltaic devices with the structure of indium tin oxide(ITO)/poly(3,4‐ethylenedioxythiophene):poly(styrene‐sulfonate)/(BA)2(MA)n−1PbnI3n+1(n = 3,4)/6,6‐phenyl‐C61‐butyric acid methyl ester/Bathocuproine/Ag are fabricated. The devices based on (BA)2(MA)2Pb3I10 perovskite (n = 3) with the precursor composition of BAI:methylammonium iodide:PbI2:NH4SCN = 2:2:3:1 (by molar ratio) show an averaged power conversion efficiency (PCE) of 6.82%. In the case of (BA)2(MA)3Pb4I13 (n = 4), a higher PCE of 8.79% is achieved. Both of the unsealed devices perform unique stability with almost unchanged PCE during the period of storage in purified N2 glove box. This work provides a simple and effective method to enhance the efficiency of the 2D perovskite solar cell.
A new route to realize the vertical‐orientation growth of 2D layered (BA)2(MA)n−1PbnI3n+ (n = 3, 4)‐based perovskite with the aid of a NH4SCN additive through a one‐step spin‐coating method is presented. The corresponding planar‐structured solar cells present the averaged power conversion efficiency (PCE) of 6.82% (n = 3) and the best PCE of 8.79% (n = 4) with unique stability.
The compound Cu2Ni0.75Co0.25SnS4 (CNCTS) was synthesized using the spin-coating technique. Analysis via X-ray diffraction and Raman spectroscopy revealed the formation of a cubic structure at 350 °C, ...with a lattice parameter of 5.40 Å and a crystallite size of 51 A°, with no secondary phase detected. Scanning electron microscopy and energy dispersive spectroscopy examination showed that the annealed CNCTS sample at 350 °C for 1 h displayed surface morphologies that were nearly uniform, dense, and rough, with a composition close to stoichiometric. UV–Visible–Near infrared analysis indicated that the bandgap energy of the annealed CNCTS at 350 °C is 1.39 eV, rendering it highly suitable for low-cost photovoltaic applications.
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•β-PVDF@Zn anodes were developed by spin-coating, followed by heat treatment.•Flexible β-PVDF coating mitigated the uneven stripping/plating issues on Zn anode.•β-PVDF@Zn demonstrated ...significantly reduced polarization in a symmetric cell test.•Ultralong service life was realized with β-PVDF@Zn anode and V2O5/C cathode.
Aqueous zinc ion batteries (AZIBs) have gained significant attention as a viable alternative for power storage systems due to their desirable properties, including low cost, low environmental impact, and a high specific capacity of 820 mAh g−1. Nevertheless, their commercial applicability is deterred by issues such as the formation of protrusions and parasitic reactions that can severely damage the cell. In this study, the Zn anode was coated with a thin protective layer of highly polar β-phase poly(vinylidene difluoride) (β-PVDF) via a simple spin-coating process. The resilient and robust β-PVDF layer regulated the Zn stripping/plating process and also inhibited corrosion. The resulting β-PVDF-coated Zn anode (β-PVDF@Zn) exhibited superior performance compared to that of bare Zn metal and α-PVDF@Zn, with a low overpotential of 40 mV for 2000 h of operation in a symmetric cell test. Furthermore, β-PVDF prolonged the life span of a full cell to 4000 cycles with remarkable cyclic stability. This study provides a facile yet promising strategy to achieve a dendrite-free metal Zn anode.
2D hybrid halide perovskites with the formula (A′)2(A)n‐1PbnI3n+1 have remarkable stability and promising efficiency in photovoltaic and optoelectronic devices, yet fundamental understanding of film ...formation, key to optimizing these devices, is lacking. Here, in situ grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) is used to monitor film formation during spin‐coating. This elucidates the general film formation mechanism of 2D halide perovskites during one‐step spin‐coating. There are three stages of film formation: sol–gel, oriented 3D, and 2D. Three precursor phases form during the sol–gel stage and transform to perovskite, first giving a highly oriented 3D‐like phase at the air/liquid interface followed by subsequent nucleations forming slightly less oriented 2D perovskite. Furthermore, heating before crystallization leads to fewer nucleations and faster removal of the precursors, improving orientation. This outlines the primary causes of phase distribution and perpendicular orientation in 2D perovskite films and paves the way for rationally designed film fabrication techniques.
The mechanism of 2D halide perovskite film formation is resolved using in situ grazing‐incidence wide‐angle scattering (GIWAXS). The film begins as a sol–gel precursor before first forming a 3D MAPbI3‐like phase at the air/liquid interface. This acts as a template for the highly textured 2D phase with the layers perpendicular to the substrate, which grows closer to the substrate.
Thermal stability is a critical criterion for assessing the long‐term stability of perovskite solar cells (PSCs). Here, it is shown that un‐encapsulated co‐evaporated MAPbI3 (TE_MAPbI3) PSCs ...demonstrate remarkable thermal stability even in an n‐i‐p structure that employs Spiro‐OMeTAD as hole transport material (HTM). TE_MAPbI3 PSCs maintain over ≈95% and ≈80% of their initial power conversion efficiency (PCE) after 1000 and 3600 h respectively under continuous thermal aging at 85 °C. TE_MAPbI3 PSCs demonstrate remarkable structural robustness, absence of pinholes, or significant variation in grain sizes, and intact interfaces with the HTM, upon prolonged thermal aging. Here, the main factors driving TE_MAPbI3 stability are assessed. It is demonstrated that the excellent TE_MAPbI3 thermal stability is related to the perovskite growth process leading to a compact and almost strain‐stress‐free film. On the other hand, un‐encapsulated PSCs with the same architecture, but incorporating solution‐processed MAPbI3 or Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 as active layers, show a complete PCE degradation after 500 h under the same thermal aging condition. These results highlight that the control of the perovskite growth process can substantially enhance the PSCs thermal stability, besides the chemical composition. The TE_MAPbI3 impressive long‐term thermal stability features the potential for field‐operating conditions.
Long‐term thermal stability is critical for perovskite solar cells (PSCs) operation. Un‐encapsulated co‐evaporated MAPbI3 PSCs, contrary to similar spin‐coated PSCs, exhibit remarkable structural robustness and retain 80% of their initial efficiency after 3600 h aging at 85 °C. This excellent intrinsic stability is driven by the strain‐stress‐free MAPbI3 grown by co‐evaporation, where post‐annealing is not required to fully form the perovskite.
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•Achieve a record PCE of 22.46% for dopant-free AlOx/SiO2/LiF based n-type Si homojunction solar cell.•Observe a new pinhole-like carriers transport mechanism in spin-coating SiO2 ...layer.•This mechanism is the key factor for the achievement of the excellent surface passivation and electrical performance.•The AlOx/SiO2/LiF based device demonstrates promising application in high-efficiency Si and Si/Perovskite solar cells.
The wide bandgap oxide is considered a promising passivating contact for Si solar cells due to its low parasitic absorption and low-temperature process. However, the power conversion efficiencies (PCEs) of these devices remain unsatisfactory, in addition to the high annealing temperatures and complicated annealing processes. Employing the low-temperature and simple spin-coating SiO2, we in this work achieved the champion PCE of 22.46 % for the full-area dopant-free AlOx/SiO2/LiF based n-type Si passivating contact homojunction solar cell, demonstrating the significant advantages of the efficiency and process compared with other dopant-free wide bandgap oxide based solar cells. The key to success lies in the simultaneous achievement of the ultralow contact resistivity (ρc) and excellent surface passivation of the AlOx/SiO2/LiF passivating contact. Crucially, we find a novel pinhole-like carriers transport mechanism in the spin-coating 20 nm-thickness SiO2 layer, resulting in the ultralow ρc (0.244 mΩ·cm2) of the AlOx/SiO2/LiF passivating contact. The pinhole-like carriers transport in spin-coating SiO2 significantly broadens the thickness range of the interfacial passivation layer, enabling the superior performance of crystalline Si passivating contact solar cells and demonstrating promising application in high-efficiency Si and Si/Perovskite tandem solar cells by the low-temperature and simple process.
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