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Since the report in 2012 of a solid-state perovskite solar cell (PSC) with a power-conversion efficiency (PCE) of 9.7% and a stability of 500 h, intensive efforts have been made to increase the certified PCE, reaching 25.2% in 2019. The PCE of PSCs now exceeds that of conventional thin-film solar-cell technologies, and the rate at which this increase has been achieved is unprecedented in the history of photovoltaics. Moreover, the development of moisture-stable and heat-stable materials has increased the stability of PSCs. Small-area devices (<1 cm 2 ) are typically fabricated using a spin-coating method; however, this approach may not be suitable for the preparation of the large-area (>100 cm 2 ) substrates required for commercialization. Thus, materials and methods need to be developed for coating large-area PSCs. In this Review, we discuss solution-based and vapour-phase coating methods for the fabrication of large-area perovskite films, examine the progress in performance and the parameters affecting the properties of large-area coatings, and provide an overview of the methodologies for achieving high-efficiency perovskite solar modules. The scalable fabrication of perovskite solar cells and solar modules requires the development of new materials and coating methods. In this Review, we discuss solution-based and vapour-phase coating methods for large-area perovskite films and examine the progress in performance and the parameters affecting large-area coatings.

In this review paper, the residual strain of a polycrystalline halide perovskite film is systematically studied based on its structural inhomogeneity, which is closely correlated to the local carrier dynamics caused by a modulated electronic band structure. Long-range collective strain ordering is responsible for the overall structural properties, consequently determining the optoelectronic properties of the perovskite film. Notably, the perovskite phase stability is strongly affected by the internal strain, favoring a lower energy state. The important parameters affecting the residual strain in a real perovskite film, ranging from thermal stress to lattice mismatch and compositional inhomogeneity, are subsequently introduced along with their impacts on the optoelectronic properties and/or the stability of the crystals.Solar cells: The positive effects of strainMethods for using strain to improve the performance of a promising solar cell material have been reviewed by researchers in South Korea. A family of hybrid organic-inorganic semiconductors known as halide perovskites have emerged as a rival to silicon for the production of solar cells. Atomic-level physical forces, for example, the strain induced when a material is compressed, can improve the semiconductor’s optoelectronic properties. Hui-Seon Kim from Inha University in Incheon, and Nam-Gyu Park from Sungkyunkwan University in Suwon have summarized how this strain arises in perovskite thin films and the ways in which it modifies the dynamics of the material’s electrical charge carriers. The researchers used this understanding to suggest methods for strain engineering these materials to improve the performance of solar cell devices.

Perovskite solar cells with an inverted architecture provide a key pathway for commercializing this emerging photovoltaic technology because of the better power conversion efficiency and operational stability compared with the normal device structure. Specifically, power conversion efficiencies of the inverted perovskite solar cells have exceeded 25% owing to the development of improved self-assembled molecules 1 – 5 and passivation strategies 6 – 8 . However, poor wettability and agglomeration of self-assembled molecules 9 – 12 cause interfacial losses, impeding further improvement in the power conversion efficiency and stability. Here we report a molecular hybrid at the buried interface in inverted perovskite solar cells that co-assembled the popular self-assembled molecule [4-(3,6-dimethyl-9 H -carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with the multiple aromatic carboxylic acid 4,4′,4″-nitrilotribenzoic acid (NA) to improve the heterojunction interface. The molecular hybrid of Me-4PACz with NA could substantially improve the interfacial characteristics. The resulting inverted perovskite solar cells demonstrated a record certified steady-state efficiency of 26.54%. Crucially, this strategy aligns seamlessly with large-scale manufacturing, achieving one of the highest certified power conversion efficiencies for inverted mini-modules at 22.74% (aperture area 11.1 cm 2 ). Our device also maintained 96.1% of its initial power conversion efficiency after more than 2,400 h of 1-sun operation in ambient air. High efficiency in perovskite solar cells is achieved by using a molecular hybrid of a self-assembled monolayer with nitrilotribenzoic acid.

Perovskite solar cells with the formula FA 1− x Cs x PbI 3 , where FA is formamidinium, provide an attractive option for integrating high efficiency, durable stability and compatibility with scaled-up fabrication. Despite the incorporation of Cs cations, which could potentially enable a perfect perovskite lattice 1 , 2 , the compositional inhomogeneity caused by A-site cation segregation is likely to be detrimental to the photovoltaic performance of the solar cells 3 , 4 . Here we visualized the out-of-plane compositional inhomogeneity along the vertical direction across perovskite films and identified the underlying reasons for the inhomogeneity and its potential impact for devices. We devised a strategy using 1-(phenylsulfonyl)pyrrole to homogenize the distribution of cation composition in perovskite films. The resultant p–i–n devices yielded a certified steady-state photon-to-electron conversion efficiency of 25.2% and durable stability. We added out-of-plane cations to homogenize the distribution of cations in perovskite films, resulting in a solar cell with improved efficiency and stability.

Highly sensitive all-solution-based detectors based on printable polycrystalline organometallic perovskite thick films enable X-ray imaging at low radiation doses and over large areas. Printable perovskites for X-ray devices Organometallic perovskite materials have received considerable attention in recent years owing to their high sensitivity to light, which has been exploited in a range of photoconductive and photovoltaic devices. X-ray detection is another particularly promising application for these materials because medical X-ray imaging machines that operate under lower doses would reduce radiation exposure. In Taek Han and colleagues demonstrate a flat-panel X-ray detector made by solution processing polycrystalline perovskites on a conventional thin-film transistor pixelated backplane, with sensitivities that are at least an order of magnitude higher than those of current commercial detectors. The approach could make low-dose X-ray imaging widely available and may also be extended to other photoconductive devices. Medical X-ray imaging procedures require digital flat detectors operating at low doses to reduce radiation health risks 1 , 2 . Solution-processed organic–inorganic hybrid perovskites have characteristics that make them good candidates for the photoconductive layer of such sensitive detectors 3 , 4 , 5 , 6 , 7 . However, such detectors have not yet been built on thin-film transistor arrays because it has been difficult to prepare thick perovskite films (more than a few hundred micrometres) over large areas (a detector is typically 50 centimetres by 50 centimetres). We report here an all-solution-based (in contrast to conventional vacuum processing) synthetic route to producing printable polycrystalline perovskites with sharply faceted large grains having morphologies and optoelectronic properties comparable to those of single crystals. High sensitivities of up to 11 microcoulombs per air KERMA of milligray per square centimetre (μC mGy air −1 cm −2 ) are achieved under irradiation with a 100-kilovolt bremsstrahlung source, which are at least one order of magnitude higher than the sensitivities achieved with currently used amorphous selenium or thallium-doped cesium iodide detectors. We demonstrate X-ray imaging in a conventional thin-film transistor substrate by embedding an 830-micrometre-thick perovskite film and an additional two interlayers of polymer/perovskite composites to provide conformal interfaces between perovskite films and electrodes that control dark currents and temporal charge carrier transportation. Such an all-solution-based perovskite detector could enable low-dose X-ray imaging, and could also be used in photoconductive devices for radiation imaging, sensing and energy harvesting.

Charge carriers’ density, their lifetime, mobility, and the existence of trap states are strongly affected by the microscopic morphologies of perovskite films, and have a direct influence on the photovoltaic performance. Here, we report on micro-wrinkled perovskite layers to enhance photocarrier transport performances. By utilizing temperature-dependent miscibility of dimethyl sulfoxide with diethyl ether, the geometry of the microscopic wrinkles of the perovskite films are controlled. Wrinkling is pronounced as temperature of diethyl ether ( T DE ) decreases due to the compressive stress relaxation of the thin rigid film-capped viscoelastic layer. Time-correlated single-photon counting reveals longer carrier lifetime at the hill sites than at the valley sites. The wrinkled morphology formed at T DE  = 5 °C shows higher power conversion efficiency (PCE) and better stability than the flat one formed at T DE  = 30 °C. Interfacial and additive engineering improve further PCE to 23.02%. This study provides important insight into correlation between lattice strain and carrier properties in perovskite photovoltaics. Perovskite morphology dictates carriers’ behaviors and defect states, and thus the ultimate performance of the material. Here, the authors investigate micro-wrinkle formation in film by varying composition and deposition condition, and further implement the optimized structure for solar cells, achieving 23% efficiency.

Solar cells employing a halide perovskite with an organic cation now show power conversion efficiency of up to 22%. However, these cells are facing issues towards commercialization, such as the need to achieve long-term stability and the development of a manufacturing method for the reproducible fabrication of high-performance devices. Here, we propose a strategy to obtain stable and commercially viable perovskite solar cells. A reproducible manufacturing method is suggested, as well as routes to manage grain boundaries and interfacial charge transport. Electroluminescence is regarded as a metric to gauge theoretical efficiency. We highlight how optimizing the design of device architectures is important not only for achieving high efficiency but also for hysteresis-free and stable performance. We argue that reliable device characterization is needed to ensure the advance of this technology towards practical applications. We believe that perovskite-based devices can be competitive with silicon solar modules, and discuss issues related to the safe management of toxic material. Perovskite solar cells have emerged as a potential low-cost alternative to existing technologies. In this Perspective, Park et al . explore a strategy for the commercialisation of perovskite solar cells.

Although sunlight-driven water splitting is a promising route to sustainable hydrogen fuel production, widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochemical apparatus. Here, we describe a highly efficient and low-cost water-splitting cell combining a state-of-the-art solution-processed perovskite tandem solar cell and a bifunctional Earth-abundant catalyst. The catalyst electrode, a NiFe layered double hydroxide, exhibits high activity toward both the oxygen and hydrogen evolution reactions in alkaline electrolyte. The combination of the two yields a water-splitting photocurrent density of around 10 milliamperes per square centimeter, corresponding to a solar-to-hydrogen efficiency of 12.3%. Currently, the perovskite instability limits the cell lifetime.

Perovskite light-emitting diodes (PeLEDs) based on three-dimensional (3D) polycrystalline perovskites suffer from ion migration, which causes overshoot of luminance over time during operation and reduces its operational lifetime. Here, we demonstrate 3D/2D hybrid PeLEDs with extremely reduced luminance overshoot and 21 times longer operational lifetime than 3D PeLEDs. The luminance overshoot ratio of 3D/2D hybrid PeLED is only 7.4% which is greatly lower than that of 3D PeLED (150.4%). The 3D/2D hybrid perovskite is obtained by adding a small amount of neutral benzylamine to methylammonium lead bromide, which induces a proton transfer from methylammonium to benzylamine and enables crystallization of 2D perovskite without destroying the 3D phase. Benzylammonium in the perovskite lattice suppresses formation of deep-trap states and ion migration, thereby enhances both operating stability and luminous efficiency based on its retardation effect in reorientation. Ion migration can induce overshoot of luminance in normal 3D perovskite light-emitting diode devices and results in reduced lifetime. Here Kim et al. show that the ion migration and overshoot can be suppressed in 3D/2D hybrid perovskites, leading to 21 times longer operational lifetime.

Although perovskite solar cells (PSCs) are promising next generation photovoltaics, the production of PSCs might be hampered by complex and inefficient procedures. This Review outlines important advances in materials and methods for the cost-effective manufacturing of PSCs, including precursor synthesis, selection criteria for precursors based on chemistry, additive engineering, and deposition techniques. The goal of these technologies is not only to improve the performance and stability of PSCs, but also to significantly reduce their manufacturing costs. These advances are critical to the commercialization of PSCs, in terms of making them viable and cost-effective.The scalable and cost-effective synthesis of perovskite solar cells is dependent on materials chemistry and the synthesis technique. This Review discusses these considerations, including selecting a suitable perovskite pre-cursor, additive engineering, and the deposition process.