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• We present cesium formate as a versatile chemical additive that serves to both passivate defects in perovskite solar cells and improve roll-to-roll processability. • The cesium and formate ions successfully passivate surface defects by facilitating robust interactions between the molecules and perovskite components. • Incorporating the chemical additive leads to enhanced crystalline properties in roll-to-roll processed perovskite solar cells, resulting in a power conversion efficiency exceeding 14%. Organic–inorganic halide perovskites have significant potential for application in next-generation solar cells. However, their applications are limited by challenges associated with large-area processability and long-term stability owing to the presence of pinholes and defect sites. Here, we incorporated cesium formate in a perovskite active layer using a sequential perovskite fabrication process to eliminate the defect sites of perovskites and improve the film processability via roll-to-roll (R2R) processing. The addition of cesium formate salt to the PbI 2 layer influences the perovskite crystal formation behavior as well as increases the perovskite crystallinity and decreases the defect density. Furthermore, cesium formate addition eliminated small PbI 2 grains and smoothed the perovskite surface, resulting in a large crystal grain size. The formate ions interact with the PbI 2 component and passivate halide vacancy defects, reducing nonradiative recombination and improving charge transfer. Additionally, the treated perovskite films were highly stable in air, exhibiting improved efficiency retention over time and achieving a power conversion efficiency (PCE) of > 22% compared to the control. Furthermore, the additive-treated perovskite film was processed using the R2R method, achieving a high PCE of >14% with minimal hysteresis. [Display omitted] [ABSTRACT FROM AUTHOR]

Roll‐to‐roll (R2R) fabrication of high‐performance perovskite solar cells (PSCs) remains challenging for PSC commercialization. Herein, the R2R‐suitable electron transfer layer (ETL) SnO2ink system for flexible PSCs is investigated. Water‐dispersed SnO2inks, commonly used for flexible PSCs, form dewetting pinholes during R2R slot‐die coating owing to slower evaporation compared to spin coating. To prevent the dewetting of the pinhole, a low surface tension solvent (isopropyl alcohol, IPA) is added to the SnO2ink. The IPA addition reduced surface tension, enhancing wetting behavior, but increased SnO2nanoparticles (NPs) aggregation. Interestingly, the fabricated ETL films with highly aggregated SnO2NPs are smooth, in contrast to the rough layers obtained via the spin‐coating process, owing to the high shear rate. Herein, NP aggregation and surface morphology are explored using Brownian dynamics simulations under shear conditions. Consequently, when the particles are agglomerated, the PSCs with slot‐die coating exhibit higher power conversion efficiency compared to ETL spin‐coated PSCs. Therefore, IPA addition to SnO2ink is preferred for the R2R slot‐die process by improving the wetting properties and forming smooth films. In this study, a framework is provided for obtaining high‐quality films using the slot‐die coating of ETL and promotes the commercialization of PSCs. WSnO2ink is studied as an electron transport material suitable for the roll‐to‐roll (R2R) perovskite solar cell (PSC) manufacturing system. By adding isopropyl alcohol to the SnO2ink, the wetting property is improved but the SnO2particles are aggregated. However, found out that the highly aggregated particles can form smooth films and highly efficient PSCs, unlike spin coating.

The development of a stable roll-to-roll (R2R) process for flexible large-area perovskite solar cells (PSCs) and modules is a pressing challenge. In this study, we introduced a new R2R PSC manufacturing system that employs a two-step deposition method for coating perovskite and uses intensive pulsed light (IPL) for annealing. This system has successfully fabricated small-sized cells and the first-ever large-sized, R2R-processed flexible modules. A key focus of our work was to accelerate the conversion of PbI2to perovskite. To this end, we utilized IPL annealing and incorporated additives into the PbI2layer. With these modifications, the R2R-processed perovskite films achieved a power conversion efficiency (PCE) of 16.87%, representing the highest reported value for R2R two-step processed PSCs. However, these cells exhibited hysteresis in reverse and forward PCE measurements. To address this, we introduced a dual-annealing process consisting of IPL followed by a 2-min thermal heating step. This approach successfully reduced hysteresis, resulting in low-hysteresis, R2R-processed flexible PSCs. Moreover, we fabricated large-scale flexible modules (10 × 10 cm2) with a PCE of 11.25% using the dual-annealing system, marking a significant milestone in this field.

Achieving high mobility and bias stability is a challenging obstacle in the advancement of organic thin-film transistors (OTFTs). To this end, the fabrication of high-quality organic semiconductor (OSC) thin films is critical for OTFTs. Self-assembled monolayers (SAMs) have been used as growth templates for high-crystalline OSC thin films. Despite significant research progress in the growth of OSC on SAMs, a detailed understanding of the growth mechanism of the OSC thin films on a SAM template is lacking, which has limited its use. In this study, the effects of the structure (thickness and molecular packing) of SAM on the nucleation and growth behavior of the OSC thin films were investigated. We found that disordered SAM molecules assisted in the surface diffusion of the OSC molecules and resulted in a small nucleation density and large grain size of the OSC thin films. Moreover, a thick SAM with disordered SAM molecules on the top was found to be beneficial for the high mobility and bias stability of the OTFTs.

Despite of enormous potential in niche applications, flexible perovskite solar cells (F-PSCs) still suffer from low power conversion efficiency (PCE) compared to rigid PSCs largely because of the reduced photocurrent driven by low transmittance of their flexible substrate and transparent electrode. This paper presents a plasma-polymerized-fluorocarbon (PPFC) thin film as an antireflection (AR) coating material for enhancing the efficiency of F-PSCs. The PPFC, which are deposited on flexible polyethylene terephthalate (PET) substrates at low temperature by a mid-range frequency sputtering process, are highly transparent because of their amorphous structure. Due to the very low refractive index (~ 1.38) of PPFC over a wide wavelength range, these thin films decrease the average reflectance by 2.22% and increase the average transmittance in the visible light region by 1.40%. As a result, the AR films increase the PCE of F-PSCs from 18.6% to 20.4%. The thin films have a self-cleaning effect due to their hydrophobic surface, excellent mechanical flexibility (bending radius: 4 mm), and high chemical stability. Accordingly, the thin films improve the long-term stability of F-PSCs in humid environments. Finally, these AR PPFC thin films can be manufactured by a roll-to-roll process, making them suitable for future use in highly efficient F-PSCs.