Impacts of Heterogeneous TiO2 and Al2O3 Composite Mesoporous Scaffold on Formamidinium Lead Trihalide Perovskite Solar Cells

Advances on the Application of Wide Band-Gap Insulating Materials in Perovskite Solar Cells

In recent years, the development of perovskite solar cells (PSCs) is advancing rapidly with their recorded photoelectric conversion efficiency reaching 25.8%. However, for the commercialization of PSCs, it is also necessary to solve their stability issue. In order to improve the device performance, various additives and interface modification strategies have been proposed. While, in many cases, they can guarantee a significant increase in efficiency, but not ensure improved stability. Therefore, materials that improve the device efficiency and stability simultaneously are urgently needed. Some wide band-gap insulating materials with stable physical and chemical properties are promising alternative materials. In this review, the application of wide band-gap insulating materials in PSCs, including their preparation methods, working roles, and mechanisms are described, which will promote the commercial application of PSCs.

A review of graphene derivative enhancers for perovskite solar cells

Due to the finite nature, health and environmental hazards currently associated with the use of fossil energy resources, there is a global drive to hasten the development and deployment of renewable energy technologies. One such area encompasses perovskite solar cells (PSCs) that have shown photoconversion efficiencies (PCE) comparable to silicon-based photovoltaics, but their commercialisation has been set back by short-term stability and toxicity issues, among others. A tremendous potential to overcome these drawbacks is presented by the emerging applications of graphene derivative-based materials in PSCs as substitutes or components, composites with other functional materials, and enhancers of charge transport, blocking action, exciton dissociation, substrate coverage, sensitisation and stabilisation. This review aims to illustrate how these highly capable carbon-based materials can advance PSCs by critically outlining and discussing their current applications and strategically identifying prospective research avenues. The reviewed works show that graphene derivatives have great potential in boosting the performance and stability of PSCs through morphological modifications and compositional engineering. This can drive the sustainability and commercial viability aspects of PSCs.

Metal oxide charge transporting layers for stable high-performance perovskite solar cells

This review summarizes the recent progress in metal oxide charge transporting layers to achieve stable high-performance perovskite solar cells.

A Three-Dimensional Branched TiO2 Photoanode with an Ultrathin Al2O3 Passivation Layer and a NiOOH Cocatalyst toward Photoelectrochemical Water Oxidation

Photoelectrochemical (PEC) water splitting provides an alternative strategy for clean and renewable hydrogen production; however, the practical application is severely limited by the low solar conversion. Herein, a novel and simple strategy has been developed to construct a 3D branched TiO₂ photoanode with an ultrathin Al₂O₃ passivation layer and NiOOH cocatalyst. The structure and properties of the as-obtained photoanodes are explored by X-ray diffraction, Mott-Schottky, electrochemical impedance spectroscopy, and open circuit voltage measurements. The as-obtained B-TiO₂/Al₂O₃/NiOOH ternary heterojunction with a high-quality contact interface exhibits improved light absorption ability, an enhanced photocurrent density of 1.42 mA/cm² at 1.23 V_RHE, high conversion efficiency (0.44% at 0.80 V_RHE), and excellent stability compared to pristine TiO₂ and alone-Al₂O₃ or NiOOH decorated TiO₂ photoanodes. Therefore, this work could offer a new approach to designing and fabricating high-quality contact interfaces between photoelectrodes and various cocatalysts.

Perovskite Crystallization Dynamics during Spin-Casting: An In Situ Wide-Angle X-ray Scattering Study

In situ wide-angle X-ray scattering (WAXS) has been measured during the spin coating process used to make the precursor films required for the formation of thin films of perovskite. A customized hollow axis spin coater was developed to permit the scattered X-rays to be collected in transmission geometry during the deposition process. Spin coating is the technique most commonly used in laboratories to make thin perovskite films. The dynamics of spin-casting MAPbI_3-x Cl _x and FAPbI_3-x Cl _x films have been investigated and compared to investigate the differences between the dynamics of MAPbI_3-x Cl _x and FAPbI_3-x Cl _x film formation. In particular, we focus on the crystallization dynamics of the precursor film formation. When casting MAPbI_3-x Cl _x , we observed relatively fast 1D crystallization of the intermediate product MA₂PbI₃Cl. There was an absence of the desired perovskite phase formed directly; it only appeared after an annealing step that converted the MA₂PbI₃Cl to MAPbI₃. In contrast, slower crystallization via a 3D precursor was observed for FAPbI_3-x Cl _x film formation compared to MAPbI_3-x Cl _x . Another important finding was that some FAPbI_3-x Cl _x perovskite was generated directly during spin-casting before annealing. These findings indicate that there are significant differences between the crystallization pathways for these two perovskite materials. These are likely to explain the differences in the lifetimes of the resulting perovskite solar cell devices produced using FA and MA cations.

Controlled Crystal Grain Growth in Mixed Cation-Halide Perovskite by Evaporated Solvent Vapor Recycling Method for High Efficiency Solar Cells

We developed a new and simple solvent vapor-assisted thermal annealing (VA) procedure which can reduce grain boundaries in a perovskite film for fabricating highly efficient perovskite solar cells (PSCs). By recycling of solvent molecules evaporated from an as-prepared perovskite film as a VA vapor source, named the pot-roast VA (PR-VA) method, finely controlled and reproducible device fabrication was achieved for formamidinium (FA) and methylammonium (MA) mixed cation-halide perovskite (FAPbI₃)_0.85(MAPbBr₃)_0.15. The mixed perovskite was crystallized on a low-temperature prepared brookite TiO₂ mesoporous scaffold. When exposed to very dilute solvent vapor, small grains in the perovskite film gradually unified into large grains, resulting in grain boundaries which were highly reduced and improvement of photovoltaic performance in PSC. PR-VA-treated large grain perovskite absorbers exhibited stable photocurrent-voltage performance with high fill factor and suppressed hysteresis, achieving the best conversion efficiency of 18.5% for a 5 × 5 mm² device and 15.2% for a 1.0 × 1.0 cm² device.

Hexagonal β-NaYF4:Yb(3+), Er(3+) Nanoprism-Incorporated Upconverting Layer in Perovskite Solar Cells for Near-Infrared Sunlight Harvesting

Hexagonal β-NaYF4:Yb(3+), Er(3+) nanoprisms, successfully prepared using a hydrothermal method, were incorporated into CH3NH3PbI3 perovskite solar cells (PSCs) as an upconverting mesoporous layer. Due to their near-infrared (NIR) sunlight harvesting, the PSCs based on the upconverting mesoporous layer exhibited a power conversion efficiency of 16.0%, an increase of 13.7% compared with conventional TiO2 nanoparticle-based PSCs (14.1%). This result suggests that the hexagonal β-NaYF4:Yb(3+), Er(3+) nanoprisms expand the absorption range of the PSC via upconversion photoluminescence, leading to an enhancement of the photocurrent.

Simultaneous enhancement in stability and efficiency of low-temperature processed perovskite solar cells

Low temperature (140 °C) processed MA_0.6FA_0.4PbI₃/AZO devices exhibit 20% higher PCE and two-fold higher device stability compared to MA_0.6FA_0.4PbI₃/ZnO devices.

A SnOx–brookite TiO2 bilayer electron collector for hysteresis-less high efficiency plastic perovskite solar cells fabricated at low process temperature

Thin plastic film-based CH₃NH₃PbI_3−xCl_x perovskite solar cells were fabricated at low process temperature using a bilayer comprising an amorphous SnO_x and mesoporous brookite TiO₂ as electron collectors.