Intrinsic and Extrinsic Determinants of Stability in Spiro-OMeTAD-Based Hole-Transporting Layers in Perovskite Solar Cells: Mechanistic Insights and Strategic Perspectives.

Spiro-OMeTAD has remained the benchmark hole-transporting material (HTM) in state-of-the-art perovskite solar cells, owing to its favorable energy level alignment and excellent interfacial compatibility. However, its practical implementation is critically hindered by the intrinsic instabilities introduced by conventional dopants such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4-tert-butylpyridine (tBP). While these dopants enhance electrical conductivity, they concurrently initiate multiple degradation pathways-including ionic migration, radical deactivation, and moisture/thermal-induced morphological failure-thereby compromising device longevity and reproducibility.

Nanoscopic Parylene Layer: Enhancing Perovskite Solar Cells Through Parylene-D Passivation.

The development of eco-friendly energy sources has advanced photovoltaic technologies, with perovskite solar cells (PSCs) emerging as promising alternatives owing to their high efficiency, low fabrication costs, and excellent optical and electronic properties. However, their commercialization is hindered by stability issues, such as ion migration, defect-induced degradation, and nonuniformity of the solution process over large areas, particularly at the perovskite/hole-transporting layer (HTL) interface. To address these challenges, chemical vapor deposition (CVD) is employed to introduce an ultrathin, uniform parylene-D layer at the perovskite/HTL interface.

Surface Engineering of Perovskite Solar Cells via the Dry-Vacuum Process: Deposition of Lead Halides and Alkylammonium Halides.

Perovskite solar cells (PSCs) have demonstrated remarkably rapid efficiency improvements mainly through spin-coating-based solution processes. While these processes offer numerous advantages, there are also several limitations, prompting research into alternative fabrication methodologies for PSCs. Meanwhile, surface engineering has been identified as one of the most critical factors for enhancing the efficiency and stability of PSCs.

Ferromagnetic Nickel as a Sustainable Reducing Agent for Tin-Lead Mixed Perovskite in Single-Junction and Tandem Solar Cells.

Narrow-bandgap (NBG) Sn-Pb mixed perovskite solar cells (PSCs) represent a promising solution for surpassing the radiative efficiency of single-junction solar cells. The unique bandgap tunability of halide perovskites enables optimal tandem configurations of wide-bandgap (WBG) and NBG subcells. However, these devices are limited by the susceptibility of Sn in the NBG bottom cell to being oxidized to Sn, creating detrimental Sn vacancies.

Highly flexible and transparent colorless polyimide substrate sandwiched between plasma polymerized fluorocarbon and InGaTiO for high performance flexible perovskite solar cells.

We integrated transparent antireflective coatings and transparent electrodes onto flexible colorless polyimide (CPI) substrates to fabricate high-performance flexible perovskite solar cells. Multifunctional PPFC/CPI/IGTO substrates were fabricated by sputtering the optimal plasma-polymerized fluorocarbon (PPFC) antireflective coating and InGaTiO (IGTO) electrode films on both sides of the CPI substrate. By applying PPFC with a low refractive index (1.

Shallow-level defect passivation by 6H perovskite polytype for highly efficient and stable perovskite solar cells.

The power conversion efficiency of perovskite solar cells continues to increase. However, defects in perovskite materials are detrimental to their carrier dynamics and structural stability, ultimately limiting the photovoltaic characteristics and stability of perovskite solar cells. Herein, we report that 6H polytype perovskite effectively engineers defects at the interface with cubic polytype FAPbI, which facilitates radiative recombination and improves the stability of the polycrystalline film.

Quantum barriers engineering toward radiative and stable perovskite photovoltaic devices.

Efficient photovoltaic devices must be efficient light emitters to reach the thermodynamic efficiency limit. Here, we present a promising prospect of perovskite photovoltaics as bright emitters by harnessing the significant benefits of photon recycling, which can be practically achieved by suppressing interfacial quenching. We have achieved radiative and stable perovskite photovoltaic devices by the design of a multiple quantum well structure with long (∼3 nm) organic spacers with oleylammonium molecules at perovskite top interfaces.

Ethanol purification enables high-quality α-phase FAPbI perovskite microcrystals for commercial photovoltaic applications.

Reliable quality and sustainable processes must be developed for commodities to enter the commercial stage. For next-generation photovoltaic applications such as perovskite solar cells, it is essential to manufacture high-quality photoactive perovskites eco-friendly processes. We demonstrate that ethanol, an ideal green solvent, can be applied to yield efficient alpha-phase FAPbI perovskite microcrystals.

Morphology and Performance Enhancement through the Strong Passivation Effect of Amphoteric Ions in Tin-based Perovskite Solar Cells.

Despite the optoelectronic similarities between tin and lead halide perovskites, the performance of tin-based perovskite solar cells remains far behind, with the highest reported efficiency to date being ≈14%. This is highly correlated to the instability of tin halide perovskite, as well as the rapid crystallization behavior in perovskite film formation. In this work, l-Asparagine as a zwitterion plays a dual role in controlling the nucleation/crystallization process and improving the morphology of perovskite film.

Rationally Designed Eco-Friendly Solvent System for High-Performance, Large-Area Perovskite Solar Cells and Modules.

The important but remained issue to be addressed to achieve the mass production of perovskite solar modules include a large-area fabrication of high-quality perovskite film with eco-friendly, viable production methods. Although several efforts are made to achieve large-area fabrication of perovskite, the development of eco-friendly solvent system, which is precisely designed to be fit to scale-up methods are still challenging. Herein, this work develops the eco-friendly solvent/co-solvent system to produce a high-quality perovskite layer with a bathing in eco-friendly antisolvent.

Transparent Electrodes with Enhanced Infrared Transmittance for Semitransparent and Four-Terminal Tandem Perovskite Solar Cells.

This report addresses indium oxide doped with titanium and tantulum with high near-infrared transparency to potentially replace the conventional indium tin oxide transparent electrode used in semitransparent perovskite devices and top cells of tandem devices. The high near-infrared transparency of this electrode is possibly explained by the lower carrier concentration, suggesting less defect sites that may sacrifice its optical transparency. Incorporating this transparent electrode into semitransparent perovskite solar cells for both the top and bottom electrodes improved the device performance through possible reduction of interfacial defect sites and modification in energy alignment.

Roll-to-roll gravure-printed flexible perovskite solar cells using eco-friendly antisolvent bathing with wide processing window.

Driven by recent improvements in efficiency and stability of perovskite solar cells (PSCs), upscaling of PSCs has come to be regarded as the next step. Specifically, a high-throughput, low-cost roll-to-roll (R2R) processes would be a breakthrough to realize the commercialization of PSCs, with uniform formation of precursor wet film and complete conversion to perovskite phase via R2R-compatible processes necessary to accomplish this goal. Herein, we demonstrate the pilot-scale, fully R2R manufacturing of all the layers except for electrodes in PSCs.

Carrier-resolved photo-Hall effect.

The fundamental parameters of majority and minority charge carriers-including their type, density and mobility-govern the performance of semiconductor devices yet can be difficult to measure. Although the Hall measurement technique is currently the standard for extracting the properties of majority carriers, those of minority carriers have typically only been accessible through the application of separate techniques. Here we demonstrate an extension to the classic Hall measurement-a carrier-resolved photo-Hall technique-that enables us to simultaneously obtain the mobility and concentration of both majority and minority carriers, as well as the recombination lifetime, diffusion length and recombination coefficient.

Achieving Long-Term Operational Stability of Perovskite Solar Cells with a Stabilized Efficiency Exceeding 20% after 1000 h.

Perovskite solar cells (PSCs) with mesoporous TiO (mp-TiO) as the electron transport material attain power conversion efficiencies (PCEs) above 22%; however, their poor long-term stability is a critical issue that must be resolved for commercialization. Herein, it is demonstrated that the long-term operational stability of mp-TiO based PSCs with PCE over 20% is achieved by isolating devices from oxygen and humidity. This achievement attributes to systematic understanding of the critical role of oxygen in the degradation of PSCs.

Gravure-Printed Flexible Perovskite Solar Cells: Toward Roll-to-Roll Manufacturing.

Recent advances in perovskite solar cells (PSCs) have resulted in greater than 23% efficiency with superior advantages such as flexibility and solution-processability, allowing PSCs to be fabricated by a high-throughput and low-cost roll-to-roll (R2R) process. The development of scalable deposition processes is crucial to realize R2R production of flexible PSCs. Gravure printing is a promising candidate with the benefit of direct printing of the desired layer with arbitrary shape and size by using the R2R process.

Efficient, stable and scalable perovskite solar cells using poly(3-hexylthiophene).

Perovskite solar cells typically comprise electron- and hole-transport materials deposited on each side of a perovskite active layer. So far, only two organic hole-transport materials have led to state-of-the-art performance in these solar cells: poly(triarylamine) (PTAA) and 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). However, these materials have several drawbacks in terms of commercialization, including high cost, the need for hygroscopic dopants that trigger degradation of the perovskite layer and limitations in their deposition processes.

Understanding how excess lead iodide precursor improves halide perovskite solar cell performance.

The presence of excess lead iodide in halide perovskites has been key for surpassing 20% photon-to-power conversion efficiency. To achieve even higher power conversion efficiencies, it is important to understand the role of remnant lead iodide in these perovskites. To that end, we explored the mechanism facilitating this effect by identifying the impact of excess lead iodide within the perovskite film on charge diffusion length, using electron-beam-induced current measurements, and on film formation properties, from grazing-incidence wide-angle X-ray scattering and high-resolution transmission electron microscopy.

Iodide management in formamidinium-lead-halide-based perovskite layers for efficient solar cells.

The formation of a dense and uniform thin layer on the substrates is crucial for the fabrication of high-performance perovskite solar cells (PSCs) containing formamidinium with multiple cations and mixed halide anions. The concentration of defect states, which reduce a cell's performance by decreasing the open-circuit voltage and short-circuit current density, needs to be as low as possible. We show that the introduction of additional iodide ions into the organic cation solution, which are used to form the perovskite layers through an intramolecular exchanging process, decreases the concentration of deep-level defects.

Indolo[3,2-]indole-based crystalline hole-transporting material for highly efficient perovskite solar cells.

We have designed and synthesized fluorinated indolo[3,2-]indole (IDID) derivatives as crystalline hole-transporting materials (HTM) for perovskite solar cells. The fluorinated IDID backbone enables a tight molecular arrangement stacked by strong π-π interactions, leading to a higher hole mobility than that of the current HTM standard, ,-spiro-OMeTAD, with a spherical shape and amorphous morphology. Moreover, the photoluminescence quenching in a perovskite/HTM film is more effective at the interface of the perovskite with as compared to that of ,-spiro-OMeTAD.

Spatial Distribution of Lead Iodide and Local Passivation on Organo-Lead Halide Perovskite.

We identify nanoscale spatial distribution of PbI on the (FAPbI)(MAPbBr) perovskite thin film and investigate the local passivation effect using confocal based optical microscopy of steady state and time-resolved photoluminescence (PL). Different from a typical scanning electron microscope (SEM) morphology study, confocal based PL spectroscopy and microscopy allow researchers to map the morphologies of both perovskite and PbI grains simultaneously, by selectively detecting their characteristic fluorescent bands using band-pass filters. In this work, we compare the perovskite samples without and with excess PbI incorporation and unambiguously reveal PbI distribution for the PbI-rich sample.

Thermal Stability of CuSCN Hole Conductor-Based Perovskite Solar Cells.

Although perovskite solar cells (PSCs) surpassing 20 % in certified power conversion efficiency (PCE) have been demonstrated with organic hole-transporting layers (HTLs), thermal degradation remains one of the key issues for practical applications. We fabricated PSCs using low temperature solution-processed CuSCN as the inorganic hole-transport layer (HTL), which possesses a highly stable crystalline structure and is robust even at high temperatures. The best-performing cell delivers a PCE of 18.

Tailoring of Electron-Collecting Oxide Nanoparticulate Layer for Flexible Perovskite Solar Cells.

Low-temperature-processed perovskite solar cells (PSCs), especially those fabricated on flexible substrates, exhibit device performance that is worse than that of high-temperature-processed PSCs. One of the main reasons for the inferior performance of low-temperature-processed PSCs is the loss of photogenerated electrons in the electron collection layer (ECL) or related interfaces, i.e.

Spectral splitting photovoltaics using perovskite and wideband dye-sensitized solar cells.

The extension of the light absorption of photovoltaics into the near-infrared region is important to increase the energy conversion efficiency. Although the progress of the lead halide perovskite solar cells is remarkable, and high conversion efficiency of >20% has been reached, their absorption limit on the long-wavelength side is ∼800 nm. To further enhance the conversion efficiency of perovskite-based photovoltaics, a hybridized system with near-infrared photovoltaics is a useful approach.

High-performance flexible perovskite solar cells exploiting Zn2SnO4 prepared in solution below 100 °C.

Fabricating inorganic-organic hybrid perovskite solar cells (PSCs) on plastic substrates broadens their scope for implementation in real systems by imparting portability, conformability and allowing high-throughput production, which is necessary for lowering costs. Here we report a new route to prepare highly dispersed Zn2SnO4 (ZSO) nanoparticles at low-temperature (<100 °C) for the development of high-performance flexible PSCs. The introduction of the ZSO film significantly improves transmittance of flexible polyethylene naphthalate/indium-doped tin oxide (PEN/ITO)-coated substrate from ∼75 to ∼90% over the entire range of wavelengths.