Yuyu Pan

Electrochemical route to fabricate film-like conjugated microporous polymers and application for organic electronics.

Film-like conjugated microporous polymers (CMPs) are fabricated by the novel strategy of carbazole-based electropolymerization. The CMP film storing a mass of counterions acting as an anode interlayer provides a significant power-conversion efficiency of 7.56% in polymer solar cells and 20.7 cd A(-1) in polymer light-emitting diodes, demonstrating its universality and potential as an electrode interlayer in organic electronics.

In Situ Electrochemical Deposition and Doping of C60 Films Applied to High‐Performance Inverted Organic Photovoltaics

Novel C(60)-based cross-linked films formed by electrodeposition are produced and used as the electron-collection layer in inverted polymer solar cells (PSCs). The electrodeposited films exhibit a low work function of 4.2 eV and the PSCs perform well, with power conversion efficiencies of up to 6.31%. This new kind of electrodeposited film affords more opportunities to develop modified electrodes with a low work function.

Separation of Electrical and Optical Energy Gaps: Selectively Adjusting the Electrical and Optical Properties for a Highly Efficient Blue Emitter

The design concept of separation of optical and electrical bandgap for wide bandgap materials is further developed in DCzSiPI. The HOMO/LUMO levels can be tuned by incorporation of PI and DCz substituents. The tetraphenylsilane core avoids the intramolecular charge transfer from DCz to PI (DCz = dimer carbazole, PI = phenanthro[9,10-d]imidazole). The allowed transitions are found to be from HOMO-1 to LUMO providing DCzSiPI with sufficient bandgap.

Electrochemical Synthesis of Transparent, Amorphous, C60‐Rich, Photoactive, and Low‐Doped Film with an Interconnected Structure

© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Fullerene (C 60 ) is one of the most investigated species in energy and biological applications [ 1 , 2 ] due to its unique physicochemical properties of electrical conductivity [ 3 ] and electron defi ciency. [ 4 ] For practical applications, including in various electronic devices, preparation of high C 60 content Electrochemical Synthesis of Transparent, Amorphous, C 60 -Rich, Photoactive, and Low-Doped Film with an Interconnected Structure

Accurate description of hybridized local and charge-transfer excited-state in donor–acceptor molecules using density functional theory

Hybridized local and charge-transfer excited state (HLCT) is a mixed state between locally-excited (LE) state and charge-transfer (CT) state, which is very useful for the molecular design of new-generation organic electroluminescence materials. Accurate description of HLCT excited state is still challenging issue by means of conventional density functional theory (DFT). In this study, we used 2 local functionals (SVWN and PBE), 7 hybrid functionals (BLYP, B3LYP, PBE0, BMK, BHHLYP, M06-2X, M06HF), and one long-range-corrected functional ωB97X to calculate the molecular geometry and excited state property, using diffuse-containing basis sets and the Polarizable Continuum Model (PCM), respectively. The results showed that ωB97X was the most reliable functional for the accurate description of HLCT state at both ground state and excited state.

Aggregation enhanced pure violet emission of a spiral meta-polyfluorene by supramolecular control of excimer formation

In π-conjugated optoelectronic functional materials, the excimer in the aggregate state drew much attention because of undesired low energy emission and fluorescence quenching. We report enhanced pure violet emission in meta-polyfluorene by restrained excimer formation in double-helix-like interchain entangled aggregates. It will be beneficial for optoelectric application of conjugated polymers, especially in the processing of film fabrication for high efficiency devices.

Phase stability, hardness and bond characteristics of ruthenium borides from first-principles

The structural stability, elastic modulus, hardness and electronic structure of RuB2−x (0 ≤ x ≤ 2) borides are systematically investigated using a first-principles approach. The calculated results indicate that the boron-poor region is more stable than the boron-rich region. Ru2B3 has a higher bulk modulus, shear modulus and Youngs modulus compared with RuB2 and RuB. Moreover, the calculated intrinsic hardness of Ru2B3, with a hexagonal structure (space group: P63/mmc), is 49.2 GPa, and is therefore a potential superhard material. The high hardness of Ru2B3 originates from triangular pyramid bonds, composed of a B–B covalent bond as the base and Ru–B covalent bonds as the two sides. The B–B and Ru–B covalent bonds in the a–c plane resist the applied load, this is the origin of the high elastic modulus and hardness.

Computational investigation on the large energy gap between the triplet excited-states in acenes

The large energy gap between the two triplet excited-states in acenes has a huge impact on their optical and electronic properties. Accurate calculation and full use of this gap have always been a major challenge in the field of organic semiconductor materials. In the present study, we focus on the precise description of the large gap between the T1 and T2 states, and taking a series of acenes (benzene, naphthalene, anthracene, tetracene, and pentacene) as examples, investigate their excited state behavior to verify the energy gap structure. The results show that the symmetry of the transition molecular orbital and the excited state properties have a great influence on the transition energy, and may be the main cause of the large energy gap.

Nanoscale phase separation in the bulk heterojunction structure of perylene bisimide and porphyrin by controlling intermolecular interactions

We demonstrate the concept of controlling phase separation behavior through designing directional intermolecular interactions. The twisted molecular configuration and intermolecular hydrogen bonds result in PBI-1 self-assembly into nanofiber aggregates of the order of tens of nanometers. In the blend of Zn-mTNP and PBI-1, the charge transfer interaction was suppressed effectively due to the unfavored π–π stacking for their twisted and planar molecular configurations. The spin-coated films of Zn-mTNP, PBI-1 and their blend have been characterized by UV-vis absorption spectra, and atomic force microscopy, revealing that the preferred phase separation structures in the nano scale were obtained.