Synthesis of a Novel Rigid Semi-Alicyclic Dianhydride and Its Copolymerized Transparent Polyimide Films’ Properties

A new series of colorless polyimides (CPIs) with outstanding thermal properties and mechanical properties were fabricated by the copolymerization of a novel dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2′-bistrifluoromethyl benzidine (TFDB). The novel dianhydride, 10-oxo-9-phenyl-9-(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetraacid dianhydride (3FPODA), possessed a rigid semi-alicyclic structure, –CF3 and phenyl side groups, and an active carbonyl group. Benefitting from the special structure of 3FPODA, the glass transition temperatures (Tg) of the new CPIs improved from 330 °C to 377 °C, the coefficient of thermal expansion (CTE) decreased from 46 ppm/K to 24 ppm/K, and the tensile strength (TS), tensile modulus (TM), and elongation at break (EB) increased from 84 MPa to 136 MPa, 3.2 GPa to 4.4 GPa, and 2.94% to 4.13% with the increasing amount of 3FPODA, respectively. Moreover, the active carbonyl group of the 3FPODA could enhance the CPI’s adhesive properties. These results render the new dianhydride 3FPODA an ideal candidate monomer for the fabrication of high-performance CPIs

Research Progress and Application of Polyimide-Based Nanocomposites

Polyimide (PI) is one of the most dominant engineering plastics with excellent thermal, mechanical, chemical stability and dielectric performance. Further improving the versatility of PIs is of great significance, broadening their application prospects. Thus, integrating functional nanofillers can finely tune the individual characteristic to a certain extent as required by the function. Integrating the two complementary benefits, PI-based composites strongly expand applications, such as aerospace, microelectronic devices, separation membranes, catalysis, and sensors. Here, from the perspective of system science, the recent studies of PI-based composites for molecular design, manufacturing process, combination methods, and the relevant applications are reviewed, more relevantly on the mechanism underlying the phenomena. Additionally, a systematic summary of the current challenges and further directions for PI nanocomposites is presented. Hence, the review will pave the way for future studies

Thermal annealing influence on poly(3-hexyl-thiophene)/phenyl-C61-butyric acid methyl ester-based solar cells with anionic conjugated polyelectrolyte as cathode interface layer

Thermal annealing dependent performance was demonstrated in poly(3-hexyl-thiophene):phenyl-C61-butyric acid methyl ester based organic photovoltaics with anionic conjugated polyelectrolyte (PFEOSO3Na) as the cathode interface layer. The best performance can be achieved when the device based PFEOSO3Na was treated by post-annealing, exhibiting about 20% higher power conversion efficiency than the control device. Atomic force microscopy studies showed that the morphology of interface layers changed under different device treatment processes, leading to various electron extraction efficiencies. Compared with different interface materials, it further demonstrated the best charge extraction efficiency in the device with PFEOSO3Na layer, due to its stronger interface dipole. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759148

Self-Assembly of 1‑Pyrenemethanol on ZnO Surface toward Combined Cathode Buffer Layers for Inverted Polymer Solar Cells

Solid alcohol 1-pyrenemethanol (PyM) was first introduced to modify the zinc oxide (ZnO) layer which is used in the inverted polymer solar cells (PSCs) as a cathode buffer layer (CBL). As a low-cost industrial product, the PyM can modify the surface defects and improve the electron mobility of ZnO CBL, which can be attributed to the self-assembly of PyM on the ZnO surface due to the hydrogen bonds and the conjugated structure in PyM. With a blend of PTB7:PC₇₁BM as active layer, the device with ZnO/PyM CBL exhibited a notable power conversion efficiency (PCE) of 8.26%, which is better than that of control devices based on bare ZnO CBL (7.26%). With the addition of PyM, the device based on PTB7-Th:PC₇₁BM showed a higher PCE of 9.10%, an obvious improvement from the 7.79% of control devices. There was no obvious change in device performance with the increase of PyM solution concentration, indicating that the device fabrications are thickness-insensitive. These results could be particularly useful in solution processing of buffer layer materials to high-efficiency organic solar cells

High Performance Soluble Polyimides from Ladder-Type Fluorinated Dianhydride with Polymorphism

A novel rigid semi-alicyclic dianhydride 9,10-difluoro-9,10-bis(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetracarboxylic acid dianhydride (8FDA) was reported, and its single crystal X-ray diffraction result revealed the existence of the polymorphic structure in this compound. The detail geometric configuration transition during the synthesized process was investigated, exhibiting a transition of from trans- to cis- when the hydroxyl groups were substituted by fluoride with diethylaminosulfur trifluoride (DAST). Compared with the dianhydride 4,4′-(Hexaflouroisopropylidene) diphthalic anhydride (6FDA) and 1S,2R,4S,5R-cyclohexanetetracarboxylic dianhydride (HPMDA), the resulting polyimide (PI) films based on 8FDA exhibited an obviously higher glass transition temperature (Tg, 401 °C) and a much lower coefficient of thermal expansion (CTE, 14 ppm K−1). This indicates that 8FDA is an ideal building block in high-performance soluble PIs with low CTE

Flexible Perovskite Solar Cells via Surface-Confined Silver Nanoparticles on Transparent Polyimide Substrates

We report about a flexible substrate incorporating surface-confined silver nanoparticles on transparent polyimide (PI). The incorporated silver nanoparticles (Ag NPs), which possessed excellent adhesive strength with the PI substrate, induced localized surface plasmon resonance and light scattering effects by changing the particle size and interparticle distance to promote light harvesting in the perovskite solar cells. Moreover, the reduced sheet resistance was beneficial for the charge extraction and transportation in the devices when high-conductivity poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS, PH1000) was deposited on the Ag NP-confined PI serving as a flexible bottom electrode. A power conversion efficiency of 10.41% was obtained for the flexible perovskite solar cells based on a Ag NP-confined PI substrate (the particle size of the Ag NPs was 25 nm mixed with 40 nm), which was obviously enhanced in all parameters. Especially, a 61% improvement existed in the short-circuit current density compared to that based on the bare PI substrates. It indicates that the substrate would be a promising candidate for the development of flexible electronics

Light Scattering in Nanoparticle Doped Transparent Polyimide Substrates

Here we demonstrate a simple and effective method of fabricating polymeric scattering substrate for flexible organic light-emitting diodes (OLEDs) that require no costly patterning, etching, or molding processes, aspects that are desirable for the commercialization of large-scale lighting panels. Systematic study of the influences of relative index of refraction, particle size, and doping concentration on transmittance and haze of transparent colorless polyimide (cPI) films was carried out. It was found that the reduction of transmittance and haze of the doped films decreases along with the decrease of the difference of refractive index between the particles and polymer matrix, and it could be compensated by the increase of particle size or doping concentration

Amphiphilic Diblock Fullerene Derivatives as Cathode Interfacial Layers for Organic Solar Cells

A new amphiphilic diblock fullerene derivative [6,6]-phenyl-C₆₁-butyricacid-4-(9,9,9′,9′-tetrakis­(3-bromopropyl)-9<i>H</i>,9′<i>H</i>-[2,2′-bifluoren]-7-yl)­phenol-(<i>N</i>,<i>N</i>,<i>N</i>-trimethylpropan-1-aminium) bromide (C₆₀-4TPB) was synthesized and applied in organic solar cells. Solvent annealing by toluene could obviously induce the self-assembly of the C₆₀-4TPB layer, which can be tested by the measurements of the water contact angle. After the treatment with toluene, a vertical-like arrangement in the ultrathin layer of the C₆₀-4TPB molecule will be formed between electron-collecting zinc oxide (ZnO) layers and the active layer (blend system of PTB7:PC₇₁BM), leading to the improvement of the interfacial compatibility between the active layer and the ZnO layer. On the top surface of the C₆₀-4TPB layer, the C₆₀ molecules can be expected to induce the enrichment of PC₇₁BM and block the hole, resulting in further increase in the open-circuit voltage (<i>V</i>_OC) and fill factor (FF). After spin-coating the C₆₀-4TPB solutions onto the ZnO layer with a concentration of 0.5 mg/mL in dimethyl sulfoxide, obviously improved performances were obtained with a power conversion efficiency of 8.07%, which can be attributed to the optimized interface morphology between hydrophilic ZnO and hydrophobic PTB7:PC₇₁BM