With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generation solar energy harvester. The high efficiency in combination with the low cost of materials and processes are the selling points of this cell over commercial silicon or other organic and inorganic solar cells. The characteristic features of perovskite materials may enable further advancement of the PCE beyond those afforded by the silicon solar cells, toward the Shockley-Queisser limit. This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovskite solar cells. Furthermore, possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.

High-Efficiency Perovskite Solar Cells.

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 ( 100 cm2) 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.

Scalable fabrication and coating methods for perovskite solar cells and solar modules

Organic–inorganic hybrid perovskites have electronic and optoelectronic properties that make them appealing in many device applications1–4. Although many approaches focus on polycrystalline materials5–7, single-crystal hybrid perovskites show improved carrier transport and enhanced stability over their polycrystalline counterparts, due to their orientation-dependent transport behaviour8–10 and lower defect concentrations11,12. However, the fabrication of single-crystal hybrid perovskites, and controlling their morphology and composition, are challenging12. Here we report a solution-based lithography-assisted epitaxial-growth-and-transfer method for fabricating single-crystal hybrid perovskites on arbitrary substrates, with precise control of their thickness (from about 600 nanometres to about 100 micrometres), area (continuous thin films up to about 5.5 centimetres by 5.5 centimetres), and composition gradient in the thickness direction (for example, from methylammonium lead iodide, MAPbI3, to MAPb0.5Sn0.5I3). The transferred single-crystal hybrid perovskites are of comparable quality to those directly grown on epitaxial substrates, and are mechanically flexible depending on the thickness. Lead–tin gradient alloying allows the formation of a graded electronic bandgap, which increases the carrier mobility and impedes carrier recombination. Devices based on these single-crystal hybrid perovskites show not only high stability against various degradation factors but also good performance (for example, solar cells based on lead–tin-gradient structures with an average efficiency of 18.77 per cent). A solution-based lithography-assisted epitaxial-growth-and-transfer method is used to fabricate single-crystal hybrid perovskites on any surface, with precise control of the thickness, area and chemical composition gradient.

A fabrication process for flexible single-crystal perovskite devices

Solution processing of semiconductors is highly promising for the high-throughput production of cost-effective electronics and optoelectronics. Although hybrid perovskites have potential in various device applications, challenges remain in the development of high-quality materials with simultaneously improved processing reproducibility and scalability. Here, we report a liquid medium annealing (LMA) technology that creates a robust chemical environment and constant heating field to modulate crystal growth over the entire film. Our method produces films with high crystallinity, fewer defects, desired stoichiometry, and overall film homogeneity. The resulting perovskite solar cells (PSCs) yield a stabilized power output of 24.04% (certified 23.7%, 0.08 cm2) and maintain 95% of their initial power conversion efficiency (PCE) after 2000 hours of operation. In addition, the 1-cm2 PSCs exhibit a stabilized power output of 23.15% (certified PCE 22.3%) and keep 90% of their initial PCE after 1120 hours of operation, which illustrates their feasibility for scalable fabrication. LMA is less climate dependent and produces devices in-house with negligible performance variance year round. This method thus opens a new and effective avenue to improving the quality of perovskite films and photovoltaic devices in a scalable and reproducible manner.

Liquid medium annealing for fabricating durable perovskite solar cells with improved reproducibility.

Recent advances of electrochemical and optical enzyme-free glucose sensors operating at physiological conditions.

Photovoltaic technologies based on perovskite absorber materials have led this optoelectronic field into a brand-new horizon. However, the present antisolvents used in the one-step spin-coating method always encounter problems with the very narrow process window. Herein, anisole is introduced into the one-step spin-coating method, and the technology is developed to fabricate perovskite thin films with ultrawide processing window with a dimethylformamide (DMF):dimethyl sulfoxide (DMSO) ratio varying from 6:4 to 9:1 in the precursor solution, anisole dripping time ranging from 5 to 25 s, and an antisolvent volume varying from 0.1 to 0.9 mL. Perovskite thin films as large as 100 cm2 are successfully fabricated using this method. Maximum photoelectric conversion efficiencies of 19.76% for small-area (0.14 cm2 ) and 17.39% for large-area (1.08 cm2 ) perovskite solar cell devices are obtained. It is also found that there are intermolecular hydrogen-bonding forces between anisole and DMF/DMSO that play critical roles in the wide process window. These results provide a deeper understanding of the crystallizing procedure of perovskite during the one-step spin-coating process.

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Antisolvent with an Ultrawide Processing Window for the One-Step Fabrication of Efficient and Large-Area Perovskite Solar Cells.

We demonstrate a novel strategy for the preparation of copper sulfide dendrite. Copper dendrite was electrodeposited on nickel foam by hydrogen gas bubbling and then, the surface of the Cu dendrite was treated by a vapor-phase sulfurization from thiourea at 185 °C for 30 min. The dendritic structure exhibits large surface area and high ability for fast electron transport. CuS dendrites electrode provides excellent performance in terms of electrocatalytic activity, response rate, and stability to glucose sensor. The CuS dendrite demonstrates a high sensitivity of 8337 μA mM −1  cm −2 in the wide linear detection range 0.001–4.9 mM with a detection limit of 0.05 μM. The CuS dendrite electrode can be a potential competitive candidate for application to biosensors.

Facile and cost-effective CuS dendrite electrode for non-enzymatic glucose sensor

Hybrid organic-inorganic halide perovskites (HPs) have garnered significant attention for use in resistive switching (RS) memory devices due to their low cost, low operation voltage, high on/off ratio, and excellent mechanical properties. However, the HP-based RS memory devices continue to face several challenges owing to the short endurance and stability of the HP film. Herein, two-dimensional/three-dimensional (2D/3D) perovskite heterojunction films were prepared via a low-temperature all-solution process and their RS behavior was investigated for the first time. The 2D/3D perovskite RS devices exhibited excellent performance with an endurance of 2700 cycles, a high on/off ratio of 106, and an operation speed of 640 μs. The calculated thermally assisted ion hopping activation energy and the results of the time-of-flight secondary ion mass spectroscopy demonstrated that the 2D perovskite layer could efficiently prevent the Ag ion migration into the 3D perovskite film. Moreover, we found that owing to its high thermal conductivity, the 2D perovskite can control the rupture of the Ag conductive filament. Thus, the 2D perovskite layer enhances endurance by controlling both Ag migration and filament rupture. Hence, this study provides an alternate strategy for improving endurance of HP-based RS memory devices.

Tailored 2D/3D Halide Perovskite Heterointerface for Substantially Enhanced Endurance in Conducting Bridge Resistive Switching Memory.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/inf2.12059

Won Bin Kim

Papers

Antisolvent with an Ultrawide Processing Window for the One-Step Fabrication of Efficient and Large-Area Perovskite Solar Cells.

Facile and cost-effective CuS dendrite electrode for non-enzymatic glucose sensor

Tailored 2D/3D Halide Perovskite Heterointerface for Substantially Enhanced Endurance in Conducting Bridge Resistive Switching Memory.

Chlorine‐modified SnO2 electron transport layer for high‐efficiency perovskite solar cells

Chemical Bath Deposition of Co-Doped TiO2 Electron Transport Layer for Hysteresis-Suppressed High-Efficiency Planar Perovskite Solar Cells