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In this study, we report the fabrication and characteristics of a self-healing polymer forming an ionically bonded network based on carboxylic acids and alkyl amines. The self-healing polymer forming an ionically bonded network is prepared from acrylic acid-containing carboxylic groups in the main chain and ammonium carboxylate salts derived from alkyl amines of varying lengths. The nature of the ion bonding between alkyl amines and carboxylic acids within the polymer matrix was analyzed using Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FT-IR). The self-healing polymer, incorporating ionically bound entities like ammonium carboxylate salts, demonstrated 100% self-healing efficiency at room temperature overnight, in contrast to the reference polymer without ion bonding. Various lengths of alkyl amines used to form ammonium carboxylate salts exhibited remarkable properties such as over 500% elongation at break, adhesive strength exceeding 300 gf, and light transmittance of over 90%, all dependent on the length of the alkyl chain. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have attracted considerable attention because of their outstanding photovoltaic performance and low fabrication cost. Conventional TiO2 ETL preparation methods require high-temperature annealing (>450 °C), which increases the fabrication cost and limits application on flexible substrates. To overcome these drawbacks, we propose a method for fabricating thin TiO2 films via sputtering at room temperature without thermal annealing. We systematically investigated the effects of the sputtering parameters, ultraviolet (UV) treatment, and thermal sintering on the properties of TiO2 ETLs for PSCs. With proper UV treatment, the sputtered TiO2 films exhibited well-matched band alignment, defect reduction, and improvements in the carrier concentration, electron mobility, and hole-blocking ability compared with thermally sintered TiO2 films. We also fabricated large-area perovskite modules using sputtered and UV-treated TiO2 films as ETLs on rigid and flexible substrates, and they had maximum power-conversion efficiencies of 18.82% and 14.61%, respectively. This study provides a simple, low-temperature route for fabricating ETLs for flexible perovskite solar modules. [ABSTRACT FROM AUTHOR]

Summary: All‐inorganic perovskites have shown promising performances with high thermal stabilities when used as photoactive materials for optoelectronic applications. Therefore, the development of cost‐effective, high‐quality, and massive production methods of all‐inorganic perovskites has emerged as an important task for the commercialization of perovskite‐based optoelectronics. We developed a facile preparation method for all‐inorganic CsPbBr3 perovskite powder by incorporating an organic ligand that enables Cs precursor to maintain high solubility during synthesis. The synthesized CsPbBr3 powder was verified for its cost‐effectiveness and high purity due to an appropriate selection of thermally‐decomposable precursors and effective removal of residue during the purification step. Furthermore, we found that the CsPbBr3 film prepared from our synthesized powder provided an improved homogeneity and a reduction of defects compared with that prepared from conventional metal halide precursor, which is attributed to the suppression of non‐stoichiometry and impurity phase. Therefore, the perovskite solar cells fabricated using our CsPbBr3 powder offered improved power conversion efficiency (PCE) of 8.19% and stability than the control device from metal halide precursor (5.90%). [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) based on organic monovalent cation (methylammonium or formamidinium) have shown excellent optoelectronic properties with high efficiencies above 22%, threatening the status of silicon solar cells. However, critical issues of long-term stability have to be solved for commercialization. The severe weakness of the state-of-the-art PSCs against moisture originates mainly from the hygroscopic organic cations. Here, rubidium (Rb) is suggested as a promising candidate for an inorganic-organic mixed cation system to enhance moisture-tolerance and photovoltaic performances of formamidinium lead iodide (FAPbI3). Partial incorporation of Rb in FAPbI3 tunes the tolerance factor and stabilizes the photoactive perovskite structure. Phase conversion from hexagonal yellow FAPbI3 to trigonal black FAPbI3 becomes favored when Rb is introduced. The authors find that the absorbance and fluorescence lifetime of 5% Rb-incorporated FAPbI3 (Rb0.05FA0.95PbI3) are enhanced than bare FAPbI3. Rb0.05FA0.95PbI3-based PSCs exhibit a best power conversion efficiency of 17.16%, which is much higher than that of the FAPbI3 device (13.56%). Moreover, it is demonstrated that the Rb0.05FA0.95PbI3 film shows superior stability against high humidity (85%) and the full device made with the mixed perovskite exhibits remarkable long-term stability under ambient condition without encapsulation, retaining the high performance for 1000 h. [ABSTRACT FROM AUTHOR]

Although the one-step deposition method has intensively been studied because of the simple and easy fabrication of perovskite films, uncontrolled crystallization of perovskite during one-step deposition often results in films with small crystallites and low surface coverage, leading to low photovoltaic performance. In this study, we have proposed the optimum processing conditions to afford a favorable crystal morphology of perovskite films for achieving high power conversion efficiency of perovskite solar cells. Two different morphologies, tree-like and flower-like morphologies, are developed depending upon the spin-coating time and post-heat treatment temperature. When the perovskite is crystallized from the liquid film after a short spin-coating time, the flower-like morphology is developed, whereas the tree-like morphology is developed when the perovskite is crystallized for a long spin-coating time. When the morphology evolution is monitored using in situ optical microscopy and X-ray diffraction to investigate the origin of the difference between tree-like and flower-like morphologies, it reveals that the CH3NH3I–PbI2–solvent complex is formed to develop the tree-like morphology before CH3NH3PbI3 crystals are formed, whereas the flower-like morphology is developed when the CH3NH3PbI3 crystals are formed directly from the liquid film without the formation of the CH3NH3I–PbI2–solvent complex. The film with a flower-like morphology, as prepared from DMSO solution, has large-sized crystallites, and the crystallites are highly orientated along (112) and (200) directions, resulting in a high PCE of 13.85%, whereas the film with a tree-like morphology has small-sized crystallites with random crystal orientation, exhibiting very low PCEs. [ABSTRACT FROM AUTHOR]

For the purpose of investigating the effect of fluorination position on D−A type conjugated polymer on photophysical and photovoltaic properties, two types of fluorinated polymere are synthesized, HF with fluorination on electron-donating unit and FH with fluorination on electron-accepting unit. Compared to non-fluorinated polymer, fluorinated polymers exhibit deeper HOMO energy levels without change of bandgap and stronger vibronic shoulder in UV−visible absorption, indicating that fluorination enhances intermolecular interaction. HF with fluorinated D unit exhibits well-developed fibril network, low bimolecular recombination and high hole mobility, which lead a high PCE of 7.10% in conventional single-junction solar cells, which is higher than the PCE (6.41%) of FH with fluorinated A unit. Therefore, this result demonstrates that fluorination on electron-donating unit in D−A polymers could be a promising strategy for achieving high performance polymer solar cells. [ABSTRACT FROM AUTHOR]

All-inorganic perovskites consisting of only inorganic elements have been recently considered as highly stable semiconductors for photoactive layer of optoelectronics applications. However, the formation of high-quality thin film and trap-reduced interface has still remains an important task, which should be solved for improving the performances of all-inorganic perovskite-based photovoltaics. Here, we adopted facile method that could reduce charge-carrier recombination by depositing a passivation agent on the top surface of the CsPbBr3 all-inorganic perovskite layer. We also found that the CsPbBr3 perovskite photovoltaic prepared from surface treatment method using n-octylammonium bromide provides an improved stability in ambient environment and 1-sun illuminating condition. Therefore, the perovskite photovoltaics fabricated from our approach offered an improved power conversion efficiency of 5.44% over that of the control device without surface treatment (4.12%). [ABSTRACT FROM AUTHOR]

In article number 1605988, Chul‐Ho Lee, Min Jae Ko, and co‐workers report the structural engineering of formamidinium lead iodide (FAPbI3) perovskite thin films by partially substituting the formamidinium cations with smaller rubidium (Rb) cations. Even traces of Rb significantly enhance photovoltaic performances and long‐term stability of perovskite solar cells. This is due to the supplement favoring complete conversion of the perovskite to its photoactive phase while offering structural stabilization. [ABSTRACT FROM AUTHOR]

The electron transport layer (ETL) is a key component of perovskite solar cells (PSCs) and must provide efficient electron extraction and collection while minimizing the charge recombination at interfaces in order to ensure high performance. Conventional bilayered TiO 2 ETLs fabricated by depositing compact TiO 2 (c-TiO 2 ) and mesoporous TiO 2 (mp-TiO 2 ) in sequence exhibit resistive losses due to the contact resistance at the c-TiO 2 /mp-TiO 2 interface and the series resistance arising from the intrinsically low conductivity of TiO 2 . Herein, to minimize such resistive losses, we developed a novel ETL consisting of an ultrathin c-TiO 2 layer hybridized with mp-TiO 2 , which is fabricated by performing one-step spin-coating of a mp-TiO 2 solution containing a small amount of titanium diisopropoxide bis(acetylacetonate) (TAA). By using electron microscopies and elemental mapping analysis, we establish that the optimal concentration of TAA produces an ultrathin blocking layer with a thickness of ∼3 nm and ensures that the mp-TiO 2 layer has a suitable porosity for efficient perovskite infiltration. We compare PSCs based on mesoscopic ETLs with and without compact layers to determine the role of the hole-blocking layer in their performances. The hybrid ETLs exhibit enhanced electron extraction and reduced charge recombination, resulting in better photovoltaic performances and reduced hysteresis of PSCs compared to those with conventional bilayered ETLs.