Xi Fan

Bendable ITO-free Organic Solar Cells with Highly Conductive and Flexible PEDOT:PSS Electrodes on Plastic Substrates

UNLABELLEDnFlexible and transparent electrodes have great potential for photon transmission and charge-carrier collection for next generation electronics compared to rigid electronics with indium tin oxide (ITO)-coated glass substrates. This study describes a comprehensive study of the electrical, morphological, optical, structural, and mechanical properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (nnnPEDOTnPSS) films treated by methanol and methanesulfonic acid (MSA), which are coated on hydrophobic flexible plastic substrates. Such a film coated on hydrophobic plastic substrates exhibits a high conductivity up to 3560 S cm(-1) and a good mechanical flexibility. Moreover, the use of the films to fabricate bendable ITO-free organic solar cells (OSCs) integrated on plastic substrates was presented. The bendable devices based on P3HT:PCBM not only exhibit a high power conversion efficiency (PCE) up to 3.92%, which is comparable to 4.30% of the rigid devices with ITO-coated glass substrates, but also keep about 80% in PCE of the initial value after 100 time bending with a bending radius of 14 mm in the ambient atmosphere. This work provides a novel route to dramatically improve the conductivity ofnnnPEDOTnPSS electrodes, as well as the mechanical flexibility of highly efficient organic electronics with the flexible electrodes.

Transfer-Printed PEDOT:PSS Electrodes Using Mild Acids for High Conductivity and Improved Stability with Application to Flexible Organic Solar Cells.

UNLABELLEDnHighly conductive, flexible, and transparent electrodes (FTEs) ofnnnPEDOTnPSS films on plastic substrates have been achieved using strong acid treatments. However, it is rare to realize a performance attenuation ofnnnPEDOTnPSS FTEs on plastic substrates and flexible optoelectronic devices because of strong acid residues in thennnPEDOTnPSS matrix. Herein, we develop a feasible transfer-printing technique using mild acids. Because of a mild and weak property of these acids and less acid residues innnnPEDOTnPSS matrix, the transferrednnnPEDOTnPSS FTEs exhibited a significant enhancement in stability, conductivity (3500 S cm(-1)), transparency, and mechanical flexibility on plastic substrates. Flexible organic solar cells with the FTEs also showed a remarkable enhancement in power conversion efficiency and stability in the ambient atmosphere. It is expected that the novel transfer-printing technique for makingnnnPEDOTnPSS FTEs is also useful in many other types of flexible optoelectronic devices.

Assembling Polyoxo‐Titanium Clusters and CdS Nanoparticles to a Porous Matrix for Efficient and Tunable H2‐Evolution Activities with Visible Light

Polyoxo-titanium clusters (PTCs) are applied to construct highly efficient ternary PTC/CdS/MIL-101 visible-light-range H2 -evolution photocatalysts. The application of PTCs not only increases the photocatalytic activities but also provides a molecular tool to tune them.

All‐Solution‐Processed Metal‐Oxide‐Free Flexible Organic Solar Cells with Over 10% Efficiency

All-solution-processing at low temperatures is important and desirable for making printed photovoltaic devices and also offers the possibility of a safe and cost-effective fabrication environment for the devices. Herein, an all-solution-processed flexible organic solar cell (OSC) using poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) electrodes is reported. The all-solution-processed flexible devices yield the highest power conversion efficiency of 10.12% with high fill factor of over 70%, which is the highest value for metal-oxide-free flexible OSCs reported so far. The enhanced performance is attributed to the newly developed gentle acid treatment at room temperature that enables a high-performance PEDOT:PSS/plastic underlying substrate with a matched work function (≈4.91 eV), and the interface engineering that endows the devices with better interface contacts and improved hole mobility. Furthermore, the flexible devices exhibit an excellent mechanical flexibility, as indicated by a high retention (≈94%) of the initial efficiency after 1000 bending cycles. This work provides a simple route to fabricate high-performance all-solution-processed flexible OSCs, which is important for the development of printing, blading, and roll-to-roll technologies.

Highly sensitive, durable and stretchable plastic strain sensors using sandwich structures of PEDOT:PSS and an elastomer

Thin-film “plastic” strain sensors can be mounted closely on textile clothing or human skin comfortably to detect human activities without any harm to the human body. However, it is a grand challenge to prepare highly sensitive and durable plastic strain sensors. Herein, we report a high-performance plastic strain sensor with a sandwich structure of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) doped with poly(vinyl alcohol) (PVA–PEDOT:PSS)/highly conductive PEDOT:PSS/polydimethylsiloxane elastomer. The strain sensor exhibited not only high sensitivities but also good durability at large strains owing to its robust structure integration and strong recoverability in conductance. More importantly, our plastic strain sensors are successfully used to monitor a series of human activities including joint/muscle motions, arterial pulsation and voice vibration, and distinguish some complex and diverse bending motions, demonstrating great potential in practical applications.

Highly efficient polymer solar cells employing natural chlorophyllin as a cathode interfacial layer

Development of green and low-cost interfacial materials is an important issue to promote the commercialization of polymer solar cells (PSC). In this study, a derivative of natural chlorophyll, called chlorophyllin (CuCN), is applied as a cathode interfacial layer (CIL) to effectively improve the charge-carrier transportation and collection of both fullerene and non-fullerene based PSCs. As a result, the high power conversion efficiency of 8.35% and 10.55% is achieved for fullerene PTB7:PC71BM-based devices and non-fullerene PBDB-T:IT-M-based devices, respectively. Notably, the natural chlorophyllin is a green food additive with low cost and solution-processability. This study demonstrates that the environment-friendly chlorophyllin is a promising CIL material to fabricate highly efficient solution-processed PSCs with a large area and low cost.

Highly efficient non-fullerene polymer solar cells enabled by novel non-conjugated small-molecule cathode interlayers

The interface strategy has been identified as an effective process to optimize the overall performance of polymer solar cells (PSCs). Herein, three novel non-conjugated small molecules comprising amino cations and sulfonate anions, as well as various core atoms of oxygen, sulfur, and sulfone, were successfully synthesized and employed as cathode interlayers (CILs) for non-fullerene PSCs. A large improvement of the device performance was observed, in which the solution processed sulfur-based CIL shows excellent cathode modification ability and device properties with the highest power conversion efficiency (PCE) of 11.30%. Compared with the vacuum deposited Ca, the non-conjugated small-molecule CILs could significantly increase the charge transport and collection capabilities, decrease the work function (WF) of the Al counter electrode, and reduce the series resistance and charge recombination at the interface. Most importantly, these simple water/alcohol soluble CILs are of great significance and suitable for the low-cost and large-area preparation of PSCs.

Dicarboxylate Ligands Oriented Assembly of {Ti3(μ3-O)} Units: From Dimer to Coordination Triangles and Rectangles

A series of dicarboxylates bridged titanium-oxo clusters with {Ti3(μ3-O)} building units have been synthesized through facile one-step solvothermal reactions. It is interesting to find that the geometric characteristics of the obtained supramolecular structures highly depend on the configuration of the applied dicarboxylate ligands. A linear dimeric [Ti3O]2L2 complex can be constructed using flexible cyclohexanedicarboxylic acid, while the introduction of rigid 2-nitro-1,4-benzenedicarboxylic acid gives rise to a triangular [Ti3O]3L3 structure. Moreover, unusual [Ti3O]4L4 rectangles have been achieved with more symmetric 5-nitro-1,3-benzenedicarboxylic acid or terephthalic acid. Furthermore, a photochromic effect is observed on the obtained complexes upon UV-vis light irradiation in the presence of alcohol.

A Methodological Study on Tuning the Thermally Activated Delayed Fluorescent Performance by Molecular Constitution in Acridine-Benzophenone Derivatives

Thermally activated delayed fluorescent (TADF) emitters are usually designed as donor-acceptor structures with large dihedral angles, which tend to incur low fluorescent efficiency, and therefore, through molecular design various strategies have been proposed to increase the efficiency of emitters; however, few studies have compared these strategies in one TADF system. In this study, a novel TADF molecule, [4-(9,9-diphenylacridin-10-yl)phenyl](phenyl)methanone (BP-DPAC), was designed as a prototype, and two derivatives, BP-Ph-DPAC and DPAC-BP-DPAC, were also prepared to represent two common approaches to enhance TADF performance. Compared with the maximum external quantum efficiency (EQE) of 6.82u2009% for BP-DPAC, organic light-emitting diodes (OLED) devices based on DPAC-BP-DPAC exhibited enhanced TADF properties with the highest maximum EQE of 18.67u2009%, owing to an additional diphenylacridine donor, whereas BP-Ph-DPAC showed non-TADF properties and exhibited the lowest EQE of 4.25u2009%, owing to the insertion of a phenyl ring between donor and acceptor.