Precise Control of Crystallization and Phase-Transition with Green Anti-Solvent in Wide-Bandgap Perovskite Solar Cells with Open-Circuit Voltage Exceeding 1.25 V.

Wide-bandgap perovskite solar cells (PSCs) have attracted a lot of attention due to their application in tandem solar cells. However, the open-circuit voltage (VOC ) of wide-bandgap PSCs is dramatically limited by high defect density existing at the interface and bulk of the perovskite film. Here, an anti-solvent optimized adduct to control perovskite crystallization strategy that reduces nonradiative recombination and minimizes VOC deficit is proposed. Specifically, an organic solvent with similar dipole moment, isopropanol (IPA) is added into ethyl acetate (EA) anti-solvent, which is beneficial to form PbI2 adducts with better crystalline orientation and direct formation of α-phase perovskite. As a result, EA-IPA (7-1) based 1.67 eV PSCs deliver a power conversion efficiency of 20.06% and a VOC of 1.255 V, which is one of the remarkable values for wide-bandgap around 1.67 eV. The findings provide an effective strategy for controlling crystallization to reduce defect density in PSCs.

Crystal Size Effect on Carrier Transport of Microscale Perovskite Junctions via Soft Contact.

To reduce the size of optoelectronic devices, it is essential to understand the crystal size effect on the carrier transport through microscale materials. Here, we show a soft contact method to probe the properties of irregularly shaped microscale perovskite crystals by employing a movable liquid metal electrode to form a self-adaptative deformable electrode-perovskite-electrode junction. Accordingly, we demonstrate that (1) the photocurrents of perovskite quantum dot films and microplatelets show profound differences regarding both the on/off ratio and the response time upon light illumination; and (2) small-size perovskite (<50 µm) junctions may show negative differential resistance (NDR) behavior, whereas the NDR phenomenon is absent in large-size perovskite junctions within the same bias regime. Our studies provide a method for studying arbitrary-shaped crystals without mechanical damage, assisting the understanding of the photogenerated carriers transport through microscale crystals.

Ruthenium based nanostructures driven by morphological controls as efficient counter electrodes for dye-sensitized solar cells.

We introduce a facile approach to use ruthenium dioxide (RuO2) and ruthenium (Ru) nanostructures as effective counter electrodes instead of using platinum (Pt) for dye-sensitized solar cells (DSSCs). RuO2 and Ru nanostructure layers on the FTO glass can be readily prepared by a simple annealing process followed by the spin coating process of the mixture solution containing amorphous RuO2·xH2O precursor and poly(ethylene oxide) (PEO) as a dispersion matrix at low temperature in air. The Ru metal nanostructure layer prepared by the reduction of RuO2 with H2 shows the highest efficiency of 6.77% in DSSC operation, which is comparable to the efficiency of the Pt electrode (7.87%).

Enhancement of the photovoltaic performance of CH3NH3PbI3 perovskite solar cells through a dichlorobenzene-functionalized hole-transporting material.

A dichlorobenzene-functionalized hole-transporting material (HTM) is developed for a CH3NH3PbI3-based perovskite solar cell. Notwithstanding the similarity of the frontier molecular orbital energy levels, optical properties, and hole mobility between the functionalized HTM [a polymer composed of 2'-butyloctyl-4,6-dibromo-3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT-BO), 3',4'-dichlorobenzyl-4,6-dibromo-3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT-DCB), and 2,6-bis(trimethyltin)-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT-EH), denoted PTB-DCB21] and the nonfunctionalized polymer [a polymer composed of thieno[3,4-b]thiophene (TT) and benzo[1,2-b:4,5-b']dithiophene (BDT), denoted PTB-BO], a higher power conversion efficiency for PTB-DCB21 (8.7%) than that for PTB-BO (7.4%) is achieved because of a higher photocurrent and voltage. The high efficiency is even obtained without including additives, such as lithium bis(trifluoromethanesulfonyl)imide and/or 4-tert-butylpyridine, that are commonly used to improve the conductivity of the HTM. Transient photocurrent-voltage studies show that the PTB-DCB21-based device exhibits faster electron transport and slower charge recombination; this might be related to better interfacial contact through intermolecular chemical interactions between the perovskite and the 3,4-dichlorobenzyl group in PTB-DCB21.

A facile and rapid process to fabricate platinum counter electrode in dye-sensitized solar cell using nanosecond pulsed laser sintering at room temperature.

To fabricate the platinum (Pt) counter electrode in dye-sensitized solar cells (DSSCs), rapid and low sintering process was carried out using nanosecond pulsed laser sintering (LS) method based on third harmonic (355 nm) of an Nd:YAG laser at room temperature. The surface morphology of LS-Pt on fluorine-doped tin oxide (FTO) electrode showed thin and compact structure, consisting of particles size of - 10-30 nm and thickness of below 30 nm. The DSSCs with the LS-Pt/FTO counter electrodes displayed the power conversion efficiency of 4.4% with short-circuit current = 9.07 mA/cm2, open-circuit voltage = 0.79 V and fill factor = 61.3.

Highly Macroporous Polyimide with Chemical Versatility Prepared from Poly(amic acid) Salt-Stabilized High Internal Phase Emulsion Template.

Macroporous polymers have gained significant attention due to their unique mass transport and size-selective properties. In this study, we focused on Polyimide (PI), a high-performance polymer, as an ideal candidate for macroporous structures. Despite various attempts to create macroporous PI (Macro PI) using emulsion templates, challenges remained, including limited chemical diversity and poor control over pore size and porosity. To address these issues, we systematically investigated the role of poly(amic acid) salt (PAAS) polymers as macrosurfactants and matrices. By designing 12 different PAAS polymers with diverse chemical structures, we achieved stable high internal phase emulsions (HIPEs) with >80 vol % internal volume. The resulting Macro PIs exhibited exceptional porosity (>99 vol %) after thermal imidization. We explored the structure-property relationships of these Macro PIs, emphasizing the importance of controlling pore size distribution. Furthermore, our study demonstrated the utility of these Macro PIs as separators in Li-metal batteries, providing stable charging-discharging cycles. Our findings not only enhance the understanding of emulsion-based macroporous polymers but also pave the way for their applications in advanced energy storage systems and beyond.

Copper-indium-selenide quantum dot-sensitized solar cells.

We present a new synthetic process of near infrared (NIR)-absorbing copper-indium-selenide (CISe) quantum dots (QDs) and their applications to efficient and completely heavy-metal-free QD-sensitized solar cells (QDSCs). Lewis acid-base reaction of metal iodides and selenocarbamate enabled us to produce chalcopyrite-structured CISe QDs with controlled sizes and compositions. Furthermore, gram-scale production of CISe QDs was achieved with a high reaction yield of ~73%, which is important for the commercialization of low-cost photovoltaic (PV) devices. By changing the size and composition, electronic band alignment of CISe QDs could be finely tuned to optimize the energetics of the effective light absorption and injection of electrons into the TiO2 conduction band (CB). These energy-band-engineered QDs were applied to QDSCs, and the quantum-confinement effect on the PV performances was clearly demonstrated. Our best cell yielded a conversion efficiency of 4.30% under AM1.5G one sun illumination, which is comparable to the performance of the best solar cells based on toxic lead chalcogenide or cadmium chalcogenide QDs.

Monitoring of 137Cs, 239+240Pu, and 90Sr in the marine environment of South Korea and their impact on marine biota: 10 years after the Fukushima accident.

This study conducted an analysis of the behavior of radionuclides and assessment their radioactive risk based on seawater and seabed sediment samples gathered from the East, South, and Yellow Seas of South Korea over the period from 2011 to 2020. The distribution for each radionuclides in seawater obtained from the East, South, and Yellow Seas were similar. However, the concentrations of 137Cs and 239+240Pu in sediments from the East Sea were observed to be higher compared to those from the South and Yellow Seas. This variation can be attributed to differences in the ocean inflow, water column properties, and seabed characteristics among the seas around South Korea. There were no statistically significant differences between the radioactive concentrations of seawater and seabed samples collected before and after the Fukushima accident, and no areas with unusually high radiation levels were detected. Using the distribution coefficient (Kds) and the concentration ratio (CR) calculated from the 2011-to-2020 data, we evaluated the radiological impact on fish. The ERICA tool was utilized to assess these data, and indicated a negligible radiological risk from radioactivity in the seawater, seabed sediments, and marine biota in the South Korean Ocean.

Perovskite single-crystal thin films: preparation, surface engineering, and application.

Perovskite single-crystal thin films (SCTFs) have emerged as a significant research hotspot in the field of optoelectronic devices owing to their low defect state density, long carrier diffusion length, and high environmental stability. However, the large-area and high-throughput preparation of perovskite SCTFs is limited by significant challenges in terms of reducing surface defects and manufacturing high-performance devices. This review focuses on the advances in the development of perovskite SCTFs with a large area, controlled thickness, and high quality. First, we provide an in-depth analysis of the mechanism and key factors that affect the nucleation and crystallization process and then classify the methods of preparing perovskite SCTFs. Second, the research progress on surface engineering for perovskite SCTFs is introduced. Third, we summarize the applications of perovskite SCTFs in photovoltaics, photodetectors, light-emitting devices, artificial synapse and field-effect transistor. Finally, the development opportunities and challenges in commercializing perovskite SCTFs are discussed.

Recent progress of eco-friendly manufacturing process of efficient perovskite solar cells.

Perovskite solar cells (PSCs) have the potential to produce solar energy at a low cost, with flexibility, and high power conversion efficiency (PCE). However, there are still challenges to be addressed before mass production of PSCs, such as prevention from degradation under external stresses and the uniform, large-area formation of all layers. Among them, the most challenging aspect of mass production of PSCs is creating a high-quality perovskite layer using environmentally sustainable processes that are compatible with industry standards. In this review, we briefly introduce the recent progresses upon eco-friendly perovskite solutions/antisolvents and film formation processes. The eco-friendly production methods are categorized into two: (1) employing environmentally friendly solvents for perovskite precursor ink/solution, and (2) replacing harmful, volatile antisolvents or even limiting their use during the perovskite film formation process. General considerations and criteria for each category are provided, and detailed examples are presented, specifically focused on the works have done since 2021. In addition, the importance of controlling the crystallization behavior of the perovskite layer is highlighted to develop antisolvent-free perovskite formation methods.

Properties and Applications of Self-Healing Polymeric Materials: A Review.

Self-healing polymeric materials, engineered to autonomously self-restore damages from external stimuli, are at the forefront of sustainable materials research. Their ability to maintain product quality and functionality and prolong product life plays a crucial role in mitigating the environmental burden of plastic waste. Historically, initial research on the development of self-healing materials has focused on extrinsic self-healing systems characterized by the integration of embedded healing agents. These studies have primarily focused on optimizing the release of healing agents and ensuring rapid self-healing capabilities. In contrast, recent advancements have shifted the focus towards intrinsic self-healing systems that utilize their inherent reactivity and interactions within the matrix. These systems offer the advantage of repeated self-healing over the same damaged zone, which is attributed to reversible chemical reactions and supramolecular interactions. This review offers a comprehensive perspective on extrinsic and intrinsic self-healing approaches and elucidates their unique properties and characteristics. Furthermore, various self-healing mechanisms are surveyed, and insights from cutting-edge studies are integrated.

Wide-Band-Gap (2.0 eV) Perovskite Solar Cells with a VOC of 1.325 V Fabricated by a Green-Solvent Strategy.

Perovskite-based tandem solar cells are promising candidates for next-generation photovoltaic devices. However, the defects caused by ion migration cause a large deficit of open-circuit voltage (VOC) in conventional wide-band-gap perovskite films. Here, we present a new strategy that employs nontoxic acetic acid and isopropanol as solvents to deposit a perovskite film with a 2.0 eV band gap in an ambient atmosphere. The in situ formed acetate anions strongly stabilize the intrinsic defects in perovskite films. These features effectively improve the phase stability of 2.0 eV Cs0.2FA0.8PbI0.9Br2.1 perovskite, allowing the VOC to reach 1.325 V and the corresponding power conversion efficiency to reach 10.62%, which is close to the state-of-art performance of perovskite solar cells employing perovskite around a 2.0 eV band gap.

Green and Facile Synthesis of Hybrid Composites with Ultralow Dielectric Properties from Water-Soluble Polyimide and Dual-Porous Silica Nanoparticles.

Here, we proposed an eco-friendly synthetic method for synthesizing hybrid composites with ultralow dielectric properties at high frequencies up to 28 GHz for true 5G communication from aqueous aromatic polyimide (PI) polymers and dual-porous silica nanoparticles (DPS). The "one-step" water-based emulsion template method was used to synthesize the macroporous silica nanoparticles (MPS). A substantially negative ζ potential was produced along the surface of MPS by the poly(vinylpyrrolidone)-based chemical functionalization, enabling excellent aqueous dispersion stability. The water-soluble poly(amic acid) (PAA), as a precursor to PI, was also "one-step" polymerized in an aqueous solution. The MPS were dispersed in a water-soluble PAA matrix to create the hybrid composite films using an entirely water-based approach. The compatibility between the PAA matrix and MPS was elucidated by investigating relatively diverse end-terminated PAAs (with either amine or carboxyl group). It was also discovered that, during a thermally activated imidization reaction, the MPS are in situ converted into the DPS with macro- and microporous structures (with a surface area of 1522.4 m2/g). The thermal, dielectric, mechanical, and morphological characteristics of each composite film were examined, while the amount of DPS in the PI matrix varied from 1 to 20 wt %. With the addition of 5 wt % DPS as an optimum condition, it showed ultralow dielectric properties, with the Dk and Df being 1.615 and 0.003 at a frequency of 28 GHz, respectively, and compatible mechanical properties, with the tensile strength and elastic modulus being 78.2 MPa and 0.32 GPa, respectively. These results can comprehensively satisfy various physical properties required as a substrate material for 5G communication devices.

Highly Self-Healable Polymeric Coating Materials Based on Charge Transfer Complex Interactions with Outstanding Weatherability.

In this study, we prepare highly self-healable polymeric coating materials using charge transfer complex (CTC) interactions. The resulting coating materials demonstrate outstanding thermal stability (1 wt% loss thermal decomposition temperature at 420 °C), rapid self-healing kinetics (in 5 min), and high self-healing efficiency (over 99%), which is facilitated by CTC-induced multiple interactions between the polymeric chains. In addition, these materials exhibit excellent optical properties, including transmittance over 91% and yellow index (YI) below 2, and show enhanced weatherability with a ΔYI value below 0.5 after exposure to UV light for 72 h. Furthermore, the self-healable coating materials developed in this study show outstanding mechanical properties by overcoming the limitations of conventional self-healing materials.

A new mussel-inspired polydopamine sensitizer for dye-sensitized solar cells: controlled synthesis and charge transfer.

The efficient electron injection by direct dye-to-TiO(2) charge transfer and strong adhesion of mussel-inspired synthetic polydopamine (PDA) dyes with TiO(2) electrode is demonstrated. Spontaneous self-polymerization of dopamine using dip-coating (DC) and cyclic voltammetry (CV) in basic buffer solution were applied to TiO(2) layers under a nitrogen atmosphere, which offers a facile and reliable synthetic pathway to make the PDA dyes, PDA-DC and PDA-CV, with conformal surface and perform an efficient dye-to-TiO(2) charge transfer. Both synthetic methods led to excellent photovoltaic results and the PDA-DC dye exhibited larger current density and efficiency values than those in the PDA-CV dye. Under simulated AM 1.5 G solar light (100 mW cm(-2)), a PDA-DC dye exhibited a short circuit current density of 5.50 mW cm(-2), corresponding to an overall power conversion efficiency of 1.2 %, which is almost 10 times that of the dopamine dye-sensitized solar cell. The PDA dyes showed strong adhesion with the nanocrystalline TiO(2) electrodes and the interface engineering of a dye-adsorbed TiO(2) surface through the control of the coating methods, reaction times and solution concentration maximized the overall conversion efficiency, resulting in a remarkably high efficiency.

Suppressed recombination in quantum dot-sensitized solar cells with blocking layers on FTO substrates.

The compact and thin TiO2 blocking layers (c-TiO2) were formed on F-doped SnO2 (FTO) substrate in quantum dots-sensitized solar cells (QSSCs) by chemical deposition. The c-TiO2 layers induced indirect contact between electrolyte and FTO electrode, which reduced leakage in QSSCs. The QSSCs showed power conversion efficiency (Eff) of 3.85% in the presence of c-TiO2 layers which leads to 21% improved compared to that without c-TiO2 layers (Eff = 3.18%). The presence of the c-TiO2 layers in QSSCs also improved the stability under illumination.

Expanding the spectral response of a dye-sensitized solar cell by applying a selective positioning method.

We have developed a facile method to position different dyes (N719 and N749) sequentially in a mesoporous TiO(2) layer through selective desorption and adsorption processes. From the selective removal of the only upper part of the first adsorbed dye, double-layered dye-sensitized solar cells have been successfully achieved without any damage to the dye. From the incident photon-to-current conversion efficiency (IPCE) measurement, the multi-layered dye-sensitized solar cell (MDSSC) was found to exhibit an expanded spectral response for the solar spectrum while maintaining the maximum IPCE value of each single-layered cell. The highest photocurrent density, 19.3 mA cm( - 2), was obtained from the MDSSC utilizing an N719/N749 bi-layered mesoporous TiO(2) film. The power conversion efficiency of 9.8% was achieved from the MDSSC, which is higher than that of single N719-or N749-based cells and cocktail-dyed (a mixture of N719 and N749) cells.

Microwave-assisted ultrafast in-situ growth of N-doped carbon quantum dots on multiwalled carbon nanotubes as an efficient electrocatalyst for photovoltaics.

Multiwalled carbon nanotubes (MWCNTs) are at the forefront of metal-free electrocatalysts, however, the performance is still limited due to lack of functionality and dispersion. Coupling of MWCNTs with nitrogen doped carbon quantum dots (NCQDs) can impart the required active sites and dispersion. For the purpose, NCQDs are generally attached to MWCNTs by multistep processing, such as NCQDs synthesis, followed by their complex purification, surface activation, and crosslinking with MWCNT. The scalability of such a multistep process is limited, which is addressed by direct microwave-assisted growth of NCQDs on MWCNT. The concentration of reactants of NCQDs synthesis was optimized (with respect to MWCNTs), to achieve controlled direct growth of NCQDs on MWCNTs. The proposed strategy significantly reduced time and energy consumption, along with providing an overlapped interface for the fast charge transfer. Moreover, NCQDs' growth effectively modulated the surface reactivity and internal band structure of the MWCNTs. In response, dye-sensitized solar cells employing NCQDs modified MWCNT as a counter electrode showed 50% higher photovoltaic performance as compared to bare MWCNTs.

Selective positioning of organic dyes in a mesoporous inorganic oxide film.

Although sequential adsorption of dyes in a single TiO(2) electrode is ideal to extend the range of light absorption in dye-sensitized solar cells, high-temperature processing has so far limited its application. We report a method for selective positioning of organic dye molecules with different absorption ranges in a mesoporous TiO(2) film by mimicking the concept of the stationary phase and the mobile phase in column chromatography, where polystyrene-filled mesoporous TiO(2) film is explored for use as a stationary phase and a Brønsted-base-containing polymer solution is developed for use as a mobile phase for selective desorption of the adsorbed dye. By controlling the desorption and adsorption depth, yellow, red and green dyes were vertically aligned within a TiO(2) film, which is confirmed by an electron probe micro-analyser. The external quantum efficiency (EQE) spectrum from a solar cell with three selectively positioned dyes reveals the EQE characteristics of each single-dye cell.

Method to protect charge recombination in the back-contact dye-sensitized solar cell.

We prepared a back-contact dye-sensitized solar cell and investigated effect of the sputter deposited thin TiO2 film on the back-contact ITO electrode on photovoltaic property. The nanocrystalline TiO2 layer with thickness of about 11 µm formed on a plain glass substrate in the back-contact structure showed higher optical transmittance than that formed on an ITO-coated glass substrate, which led to an improved photocurrent density by about 6.3%. However, photovoltage was found to decrease from 817 mV to 773 mV. The photovoltage recovered after deposition of a 35 nm-thick thin TiO2 film on the surface of the back-contact ITO electrode. Little difference in time constant for electron transport was found for the back-contact ITO electrodes with and without the sputter deposited thin TiO2 film. Whereas, time constant for charge recombination increased after introduction of the thin TiO2 film, indicating that such a thin TiO2 film protected back electron transfer, associated with the recovery of photovoltage. As the result of the improved photocurrent density without deterioration of photovoltage, the back-contact dye-sensitized solar cell exhibited 13.6% higher efficiency than the ITO-coated glass substrate-based dye-sensitized solar cell.