Low-Temperature Cross-Linkable Hole Transport Materials for Solution-Processed Quantum Dot and Organic Light-Emitting Diodes with High Efficiency and Color Purity.

Cross-linkable hole transport materials (HTMs) are ideal for improving the performance of solution-processed quantum dot light-emitting diodes (QLEDs) and phosphorescent light-emitting diodes (OLEDs). However, previously developed cross-linkable HTMs possessed poor hole transport properties, high cross-linking temperatures, and long curing times. To achieve efficient cross-linkable HTMs with high mobility, low cross-linking temperature, and short curing time, we designed and synthesized a series of low-temperature cross-linkable HTMs comprising dibenzofuran (DBF) and 4-divinyltriphenylamine (TPA) segments for highly efficient solution-processed QLEDs and OLEDs.

Efficient and Stable Fiber Dye-Sensitized Solar Cells Based on Solid-State Li-TFSI Electrolytes with 4-Oxo-TEMPO Derivatives.

Fiber-shaped dye-sensitized solar cells (FDSSCs) with flexibility, weavablity, and wearability have attracted intense scientific interest and development in recent years due to their low cost, simple fabrication, and environmentally friendly operation. Since the Grätzel group used the organic radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as the redox system in dye-sensitized solar cells (DSSCs) in 2008, TEMPO has been utilized as an electrolyte to further improve power conversion efficiency (PCE) of solar cells. Hence, the TEMPO with high catalyst oxidant characteristics was developed as a hybrid solid-state electrolyte having high conductivity and stability structure by being integrated with a lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) film for FDSSCs.

Improved device efficiency and lifetime of perovskite light-emitting diodes by size-controlled polyvinylpyrrolidone-capped gold nanoparticles with dipole formation.

Herein, an unprecedented report is presented on the incorporation of size-dependent gold nanoparticles (AuNPs) with polyvinylpyrrolidone (PVP) capping into a conventional hole transport layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The hole transport layer blocks ion-diffusion/migration in methylammonium-lead-bromide (MAPbBr)-based perovskite light-emitting diodes (PeLEDs) as a modified interlayer. The PVP-capped 90 nm AuNP device exhibited a seven-fold increase in efficiency (1.

Improved Light Harvesting of Fiber-Shaped Dye-Sensitized Solar Cells by Using a Bacteriophage Doping Method.

Fiber-shaped solar cells (FSCs) with flexibility, wearability, and wearability have emerged as a topic of intensive interest and development in recent years. Although the development of this material is still in its early stages, bacteriophage-metallic nanostructures, which exhibit prominent localized surface plasmon resonance (LSPR) properties, are one such material that has been utilized to further improve the power conversion efficiency (PCE) of solar cells. This study confirmed that fiber-shaped dye-sensitized solar cells (FDSSCs) enhanced by silver nanoparticles-embedded M13 bacteriophage (Ag@M13) can be developed as solar cell devices with better PCE than the solar cells without them.

Simple one-pot synthesis and high-resolution patterning of perovskite quantum dots using a photocurable ligand.

In this study, we report a UV-light-curable azide ligand (AzL) for the micro-patterning of PeQDs. AzL can be attached to the surface of the PeQDs during their synthesis without additional ligand exchange. Using the AzL-grafted CsPbBr PeQDs, high-color-purity 240 × 240 μm square-shaped patterns were successfully fabricated using UV light irradiation, which corresponds to a resolution of >50 pixels per inch.

All-Polymer Solar Cells Approaching 12% Efficiency with a New π-Conjugated Polymer Donor Enabled by a Nonhalogenated Solvent Process.

High efficiency and nonhalogenated solvent processing are important issues for commercial application of all-polymer solar cells (all-PSCs). In this regard, we increased the photovoltaic performance of all-PSCs to a benchmark power conversion efficiency (PCE) of 11.66% by manipulating the pre-aggregation of a new π-conjugated polymer donor (Nap-SiBTz) using toluene as a solvent.

Highly efficient, heat dissipating, stretchable organic light-emitting diodes based on a MoO/Au/MoO electrode with encapsulation.

Stretchable organic light-emitting diodes are ubiquitous in the rapidly developing wearable display technology. However, low efficiency and poor mechanical stability inhibit their commercial applications owing to the restrictions generated by strain. Here, we demonstrate the exceptional performance of a transparent (molybdenum-trioxide/gold/molybdenum-trioxide) electrode for buckled, twistable, and geometrically stretchable organic light-emitting diodes under 2-dimensional random area strain with invariant color coordinates.

Printable Free-Standing Hybrid Graphene/Dry-Spun Carbon Nanotube Films as Multifunctional Electrodes for Highly Stable Perovskite Solar Cells.

Perovskite solar cells (PSCs) have attracted immense attention owing to their outstanding power conversion efficiency (PCE). However, their counter electrodes are commonly produced by evaporating metals, such as Ag and Au, under high vacuum conditions, which make the PSCs costly, thereby limiting their large-scale production. In this study, a free-standing hybrid graphene/carbon nanotube film was carefully designed to replace noble metal PSC counter electrodes to reduce the cost and increase the stability of PSCs.

Fractional structured molybdenum oxide catalyst as counter electrodes of all-solid-state fiber dye-sensitized solar cells.

A novel hierarchical solution-processed fractional structured molybdenum oxide (MoO) catalyst is fabricated from tricarbonyltris (propionitrile) molybdenum and used as the counter electrode of all-solid-state fiber-shaped dye-sensitized solar cells (S-FDSSC). The Tafel plot results and electrical impedance spectroscopy suggest that the use of the fractional structured MoO catalyst enhances the efficiency of the reduction of I to 3I at the counter electrode/electrolyte interface. Because of the improvements of the short-current circuit and fill factor, the power conversion efficiency of the MoO-modified S-FDSSC improves by 60% compared with that of the reference S-FDSSC.

Enhancement of Photoluminescence Quantum Yield and Stability in CsPbBr Perovskite Quantum Dots by Trivalent Doping.

We determine the influence of substitutional defects on perovskite quantum dots through experimental and theoretical investigations. Substitutional defects were introduced by trivalent dopants (In, Sb, and Bi) in CsPbBr by ligand-assisted reprecipitation. We show that the photoluminescence (PL) emission peak shifts toward shorter wavelengths when doping concentrations are increased.

Clean interface without any intermixed state between ultra-thin P3 polymer and CHNHPbI hybrid perovskite thin film.

Hole transport layers (HTL) are crucial materials to improve the power conversion efficiency in organohalide hybrid perovskite-based solar-cell applications. Two important physical properties are required in HTL materials: good hole mobility and air-protection. After HTL solution-based deposition, an intermixed chemical state at the interface between HTL and hybrid perovskite is key to confirming the physical property of HTL.

Replacement of n-type layers with a non-toxic APTES interfacial layer to improve the performance of amorphous Si thin-film solar cells.

Hydrogenated amorphous Si (a-Si:H) thin-film solar cells (TFSCs) generally contain p/n-type Si layers, which are fabricated using toxic gases. The substitution of these p/n-type layers with non-toxic materials while improving the device performance is a major challenge in the field of TFSCs. Herein, we report the fabrication of a-Si:H TFSCs with the n-type Si layer replaced with a self-assembled monolayer (3-aminopropyl) triethoxysilane (APTES).

Efficient Approach for Improving the Performance of Nonhalogenated Green Solvent-Processed Polymer Solar Cells via Ternary-Blend Strategy.

The ternary-blend approach has the potential to enhance the power conversion efficiencies (PCEs) of polymer solar cells (PSCs) by providing complementary absorption and efficient charge generation. Unfortunately, most PSCs are processed with toxic halogenated solvents, which are harmful to human health and the environment. Herein, we report the addition of a nonfullerene electron acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3- d:2',3'- d']- s-indaceno[1,2- b:5,6- b']dithiophene (ITIC) to a binary blend (poly[4,8-bis(2-(4-(2-ethylhexyloxy)3-fluorophenyl)-5-thienyl)benzo[1,2- b:4,5- b']dithiophene- alt-1,3-bis(4-octylthien-2-yl)-5-(2-ethylhexyl)thieno[3,4- c]pyrrole-4,6-dione] (P1):[6,6]-phenyl-C-butyric acid methyl ester (PCBM), PCE = 8.

An Efficient Amphiphilic-Type Triphenylamine-Based Organic Hole Transport Material for High-Performance and Ambient-Stable Dopant-Free Perovskite and Organic Solar Cells.

A new set of simply structured triphenylamine-based small molecules are synthesized and evaluated as dopant-free hole transporting materials (HTMs) for high-performance perovskite solar cells (PSCs) and bulk heterojunction inverted organic solar cells (BHJ IOSCs). Surprisingly, the new amphiphilic-type HTM-1 (with internal hydrophilic groups and peripheral hydrophobic alkyl tails) showed better compatibility and performance than the actual target molecule, that is, HTM-2 in PSCs and BHJ IOSCs. Importantly, the HTM-1-based dopant-free PSCs and BHJ IOSCs exhibited high power conversion efficiencies (PCEs) of 11.

Optical Transmittance Enhancement of Flexible Copper Film Electrodes with a Wetting Layer for Organic Solar Cells.

The development of highly efficient flexible transparent electrodes (FTEs) supported on polymer substrates is of great importance to the realization of portable and bendable photovoltaic devices. Highly conductive, low-cost Cu has attracted attention as a promising alternative for replacing expensive indium tin oxide (ITO) and Ag. However, highly efficient, Cu-based FTEs are currently unavailable because of the absence of an efficient means of attaining an atomically thin, completely continuous Cu film that simultaneously exhibits enhanced optical transmittance and electrical conductivity.

Accomplishment of Multifunctional π-Conjugated Polymers by Regulating the Degree of Side-Chain Fluorination for Efficient Dopant-Free Ambient-Stable Perovskite Solar Cells and Organic Solar Cells.

We present an efficient approach to develop a series of multifunctional π-conjugated polymers (P1-P3) by controlling the degree of fluorination (0F, 2F, and 4F) on the side chain linked to the benzodithiophene unit of the π-conjugated polymer. The most promising changes were noticed in optical, electrochemical, and morphological properties upon varying the degree of fluorine atoms on the side chain. The properly aligned energy levels with respect to the perovskite and PCBM prompted us to use them in perovskite solar cells (PSCs) as hole-transporting materials (HTMs) and in bulk heterojunction organic solar cells (BHJ OSCs) as photoactive donors.

Triazine-based Polyelectrolyte as an Efficient Cathode Interfacial Material for Polymer Solar Cells.

A novel polyelectrolyte containing triazine (TAZ) and benzodithiophene (BDT) scaffolds with polar phosphine oxide (P═O) and quaternary ammonium ions as pendant groups, respectively, in the polymer backbone (PBTAZPOBr) was synthesized to use it as a cathode interfacial layer (CIL) for polymer solar cell (PSC) application. Owing to the high electron affinity of the TAZ unit and P═O group, PBTAZPOBr could behave as an effective electron transport material. Due to the polar quaternary ammonium and P═O groups, the interfacial dipole moment created by PBTAZPOBr substantially reduced the work function of the metal cathode to afford better energy alignment in the device, thus enabling electron extraction and reducing recombination of excitons at the photoactive layer/cathode interface.

High-Performance Long-Term-Stable Dopant-Free Perovskite Solar Cells and Additive-Free Organic Solar Cells by Employing Newly Designed Multirole π-Conjugated Polymers.

Perovskite solar cells (PSCs) and organic solar cells (OSCs) are promising renewable light-harvesting technologies with high performance, but the utilization of hazardous dopants and high boiling additives is harmful to all forms of life and the environment. Herein, new multirole π-conjugated polymers (P1-P3) are developed via a rational design approach through theoretical hindsight, further successfully subjecting them into dopant-free PSCs as hole-transporting materials and additive-free OSCs as photoactive donors, respectively. Especially, P3-based PSCs and OSCs not only show high power conversion efficiencies of 17.

Highly Efficient Organic Hole Transporting Materials for Perovskite and Organic Solar Cells with Long-Term Stability.

Small molecules based on N-atom-linked phenylcarbazole-fluorene as the main scaffold, end-capped with spirobifluorene derivatives, are developed as organic hole-transporting materials for highly efficient perovskite solar cells (PSCs) and bulk heterojunction (BHJ) inverted organic solar cells (IOSCs). The CzPAF-SBF-based devices show remarkable device performance with excellent long-term stability in PSCs and BHJ IOSCs with a maximum PCE of 17.21% and 7.

Stable ultrathin partially oxidized copper film electrode for highly efficient flexible solar cells.

Advances in flexible optoelectronic devices have led to an increasing need for developing highly efficient, low-cost, flexible transparent conducting electrodes. Copper-based electrodes have been unattainable due to the relatively low optical transmission and poor oxidation resistance of copper. Here, we report the synthesis of a completely continuous, smooth copper ultra-thin film via limited copper oxidation with a trace amount of oxygen.

Charge-transfer-based gas sensing using atomic-layer MoS2.

Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood.

Highly efficient and bendable organic solar cells using a three-dimensional transparent conducting electrode.

A three-dimensional (3D) transparent conducting electrode, consisting of a quasi-periodic array of discrete indium-tin-oxide (ITO) nanoparticles superimposed on a highly conducting oxide-metal-oxide multilayer using ITO and silver oxide (AgOx) as oxide and metal layers, respectively, is synthesized on a polymer substrate and used as an anode in highly flexible organic solar cells (OSCs). The 3D electrode is fabricated using vacuum sputtering sequences to achieve self-assembly of distinct ITO nanoparticles on a continuous ITO-AgOx-ITO multilayer at room-temperature without applying conventional high-temperature vapour-liquid-solid growth, solution-based nanoparticle coating, or complicated nanopatterning techniques. Since the 3D electrode enhances the hole-extraction rate in OSCs owing to its high surface area and low effective series resistance for hole transport, OSCs based on this 3D electrode exhibit a power conversion efficiency that is 11-22% higher than that achievable in OSCs by means of conventional planar ITO film-type electrodes.