Materials with low crystal symmetry often exhibit anisotropic properties, allowing the tuning of their physical and chemical properties via crystallographic orientation and exposed facet control. ...Herein, for the first time, we have demonstrated that pristine BiVO4 with a preferred 001 growth orientation and exposed (001) facets exhibits excellent intrinsic charge transport properties and surface reactivity. Using preferentially 001-oriented BiVO4 (p-BVO) as a photoanode for photoelectrochemical water splitting, an impressive photocurrent density at 1.23 V vs. the reversible hydrogen electrode (RHE) is achieved, which is approximately 16 times higher than that exhibited by a photoanode based on randomly oriented BiVO4. Importantly, when the surface of p-BVO is further roughened and decorated with an oxygen evolution electrocatalyst, photocurrent densities of ∼3.5 and ∼6.1 mA cm−2 are achieved at 0.6 and 1.23 VRHE, respectively; the latter value corresponds to ∼82% of the theoretically achievable photocurrent density for BiVO4 under 1 sun illumination. Our results demonstrate the effectiveness of crystal orientation and exposed facet control in optimizing materials for solar water-splitting applications.
One of the most effective methods to achieve high‐performance perovskite solar cells (PSCs) is to employ additives as crystallization agents or to passivate defects. Tri‐iodide ion has been known as ...an efficient additive to improve the crystallinity, grain size, and morphology of perovskite films. However, the generation and control of this tri‐iodide ion are challenging. Herein, an efficient method to produce tri‐iodide ion in a precursor solution using a photoassisted process for application in PSCs is developed. Results suggest that the tri‐iodide ion can be synthesized rapidly when formamidinium iodide (FAI) dissolved isopropyl alcohol (IPA) solution is exposed to LED light. Specifically, the photoassisted FAI–IPA solution facilitates the formation of fine perovskite films with high crystallinity, large grain size, and low trap density, thereby improving the device performance up to 22%. This study demonstrates that the photoassisted process in FAI dissolved IPA solution can be an alternative strategy to fabricate highly efficient PSCs with significantly reduced processing times.
This work proposes an efficient method to produce tri‐iodide ions, which has been known as an efficient additive that improves the crystallinity, grain size, and morphology of perovskite films in a precursor solution using a photoassited process within short time, resulting in a device performance up to 22%.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Perovskite solar cells are promising candidates for realizing an efficient, flexible, and lightweight energy supply system for wearable electronic devices. For flexible perovskite solar cells, ...achieving high power conversion efficiency (PCE) while using a low-temperature technology for the fabrication of a compact charge collection layer is a critical issue. Herein, we report on a flexible perovskite solar cell exhibiting 12.2% PCE as a result of the employment of an annealing-free, 20 nm thick, amorphous, compact TiO sub(x) layer deposited by atomic layer deposition. The excellent performance of the cell was attributed to fast electron transport, verified by time-resolved photoluminescence and impedance studies. The PCE remained the same down to 0.4 sun illumination, as well as to a 45 degree tilt to incident light. Mechanical bending of the devices worsened device performance by only 7% when a bending radius of 1 mm was used. The devices maintained 95% of the initial PCE after 1000 bending cycles for a bending radius of 10 mm. Degradation of the device performance by the bending was the result of crack formation from the transparent conducting oxide layer, demonstrating the potential of the low-temperature-processed TiO sub(x) layer to achieve more efficient and bendable perovskite solar cells, which becomes closer to a practical wearable power source.
•Electron injection and transport properties of mesoporous layer containing TiO2 nanoparticles are investigated.•The photovoltaic properties are poor with small TiO2 particles and thick mesoporous ...layers.•This poor performance is due to the increase of the area of the TiO2/TiO2 interface.•The TiO2/TiO2 interfacial resistance largely influences the photovoltaic parameters.
Mesoporous TiO2 (mp-TiO2) layers are commonly used as electron transport layers in perovskite solar cells, which help to extract electrons from the perovskite light-absorbing layer and transport them to the electrodes. We investigated the effects of the layer thickness of mp-TiO2 and particle size of TiO2 on photovoltaic properties, in terms of the surface area of the mp-layer and the interfacial areas of the TiO2 nanoparticles in the mp-layer. Various mp-TiO2 layers with thicknesses of 150, 250, and 400 nm and particle sizes of 25 nm and 41 nm were prepared to compare the photovoltaic properties of such layer-containing perovskite solar cells. Time-resolved photoluminescence decay and impedance studies showed that interfacial resistance as well as perovskite-to-TiO2 charge injection are important factors affecting photovoltaic performance. The deterioration of the photovoltaic parameters with increasing TiO2/TiO2 interfacial area also confirms that the interfacial series resistance that arises from these connections should be reduced to enhance the performance of mesoscopic perovskite solar cells.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A general doping strategy, using a wide range of acids with different pKa values as additive, is demonstrated to enhance the conductivity of spiro‐OMeTAD, the dominant hole transport material in ...perovskite solar cells (PSCs). Hysteresis‐less planar PSCs with ≈19% efficiency and better open‐circuit voltage and fill factor is achieved with acid doped spiro‐OMeTAD.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Maximizing the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells that can exceed the Shockley-Queisser single-cell limit requires a high-performing, stable perovskite top ...cell with a wide bandgap. We developed a stable perovskite solar cell with a bandgap of ~1.7 electron volts that retained more than 80% of its initial PCE of 20.7% after 1000 hours of continuous illumination. Anion engineering of phenethylammonium-based two-dimensional (2D) additives was critical for controlling the structural and electrical properties of the 2D passivation layers based on a lead iodide framework. The high PCE of 26.7% of a monolithic two-terminal wide-bandgap perovskite/silicon tandem solar cell was made possible by the ideal combination of spectral responses of the top and bottom cells.
Perovskite microcells have a great potential to be applied to diverse types of optoelectronic devices including light-emitting diodes, photodetectors, and solar cells. Although several perovskite ...fabrication methods have been researched, perovskite microcells without a significant efficiency drop during the patterning and fabrication process could not be developed yet. We herein report the fabrication of high-efficiency perovskite microcells using swelling-induced crack propagation and the application of the microcells to colored solar windows. The key procedure is a swelling-induced lift-off process that leads to patterned perovskite films with high-quality interfaces. Thus, a power conversion efficiency (PCE) of 20.1 % could be achieved with the perovskite microcell, which is nearly same as the PCE of our unpatterned perovskite photovoltaic device (PV). The semi-transparent PV based on microcells exhibited a light utilization efficiency of 4.67 and a color rendering index of 97.5 %. The metal-insulator-metal structure deposited on the semi-transparent PV enabled to fabricate solar windows with vivid colors and high color purity.
Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite ...absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3-xBrx (MAPbI3-xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3-xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I-Br anion exchange reaction, yielding poorer device performance. This MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.
Perovskite solar cells (PSCs) are the most promising candidates as next‐generation solar energy conversion systems. To design a highly efficient PSC, understanding electronic properties of mesoporous ...metal oxides is essential. Herein, we explore the effect of Nb doping of TiO2 on electronic structure and photovoltaic properties of PSCs. Light Nb doping (0.5 and 1.0 at %) increased the optical band gap slightly, but heavy doping (5.0 at %) distinctively decreased it. The relative Fermi level position of the conduction band is similar for the lightly Nb‐doped TiO2 (NTO) and the undoped TiO2 whereas that of the heavy doped NTO decreased by as much as ∼0.3 eV. The lightly doped NTO‐based PSCs exhibit 10 % higher efficiency than PSCs based on undoped TiO2 (from 12.2 % to 13.4 %) and 52 % higher than the PSCs utilizing heavy doped NTO (from 8.8 % to 13.4 %), which is attributed to fast electron injection/transport and preserved electron lifetime, verified by transient photocurrent decay and impedance studies.
Nb‐doped TiO2 nanoparticles for perovskite solar cell: TiO2 nanoparticles doped with n‐type Nb5+ have a diameter of 30 nm and a pure anatase phase; they are used for fabricating perovskite solar cells. Light doping increases the photovoltaic energy conversion efficiency by 10 % due to improved electron injection/transport properties of the nanoparticle‐based electron transport layer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Here, we examine grain boundaries (GBs) with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films ...using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier at GBs. Even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.
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