A facile approach enhancing electron extraction in zinc oxide (ZnO) electron transfer interlayer and improving performance of bulk-heterojunction (BHJ) polymer solar cells (PSCs) by adding cetyltrimethylammonium bromide (CTAB) into sol-gel ZnO precursor solution was demonstrated in this work. The power conversion efficiency (PCE) has a 24.1% increment after modification. Our results show that CTAB can dramatically influence optical, electrical and morphological properties of ZnO electron transfer layer, and work as effective additive to enhance the performance of bulk- heterojunction polymer solar cells.
The high efficiency of polymer light-emitting diodes (PLED) with ternary electron injection layers (EILs) including tetraoctylammonium bromide (TOAB), poly (vinylpyrrolidone) (PVP) and polyethylenimine (PEIE) to comprise PEIE-PVP-TOAB (E-P-T) EIL that has been achieved and well-studied via mixture design. In the unary system, TOAB can construct interfacial dipole via self-assembly crystallization atop various conjugated polymer surfaces to elevate the vacuum level of cathode. When employing three EILs as ternary system, the electrical property of PLED was further improved. The optimum luminescence efficiency respectively are 13.4 cd/A and 13.5 cd/A for T-P-D and E-P-T based PLED. In the ternary system (E-P-T), PEIE , PVP, and TOAB respectively provides electron injection, hole blocking, and polymer intersecting in the ternary based devices. The intersecting between PEIE and PVP by TOAB was evidenced by roughness change from AFM images.
We report highly efficient blue polymer light-emitting diodes (PLEDs) achieved by
introducing two nanoscale interfacial layer, made of poly(fluorine-co-triphrnylamine) [PFO-TPA] and cesium
carbonate (Cs<sub>2</sub>CO<sub>3</sub>), between (1) the PEDOT:PSS and blue poly[9,9-diarylfluorene-co-2,5-Bisphenyl-1,3,4-
oxadiazole] (P1)and (2) the aluminum cathode and the P1 emitter, individually. PFO-TPA with highest
occupied molecular orbital level (-5.36 eV) lies between those of PEDOT:PSS (~5.0 ~ 5.2 eV) and P1 emitter
(~5.54 eV), forming a stepwise energy ladder to facilitate the hole injection. For Cs<sub>2</sub>CO<sub>3</sub>, firstly, it enhances the
injection of electrons by providing an lower electron injection barrier. Secondly, applied Cs<sub>2</sub>CO<sub>3</sub> buffer
decreases the PL intensity slowly down to ~96 % of the pristine P1 film, located at 422 nm, is less efficiency
quenched than the Calcium (Ca). Therefore the overall electron injection attributed by Cs<sub>2</sub>CO<sub>3</sub> buffer is higher.
Thirdly, the device with Cs<sub>2</sub>CO<sub>3</sub> buffer did not show the low-energy emission band originated from the
fluorenone defects which are often introduced by Ca, thus stabilized blue emission from devices with high
brightness can be demonstrated. Based on the hole-transporting PFO-TPA and the Cs<sub>2</sub>CO<sub>3</sub>/Al cathode, we
obtained device efficiency and brightness as high as 13.99 cd A<sup>-1 </sup>and 35054 cd m<sup>-2</sup>, which is an improvement by
two orders of magnitude higher over devices using Ca/Al as cathode and without hole-transporting PFO-TPA.
The main purposes of this study are replacing conventional hydro-thermal method by microwave heating
using water as reaction medium to rapidly synthesize TiO<sub>2</sub>.Titanium tetraisopropoxide (TTIP) was hydrolyzed in
water. The solution is subsequently processed with microwave heating for crystal growth. The reaction time could
be shortened into few minutes. Then we chose different acids as dispersion agents to prepare TiO<sub>2</sub> paste for
investigating the effects of dispersion on the power conversion efficiency of dye-sensitized solar cells (DSCs). The
photovoltaic performance of the microwave-assisted synthesized TiO<sub>2</sub> achieved power conversion efficiency of
6.31% under AM 1.5 G condition (100 mW/cm<sup>2</sup>). This PCE value is compatible with that of the devices made from
This study investigated theoretically and experimentally that two-photon excited fluorescence is enhanced and
quenched via surface plasmons (SPs) excited by total internal reflection with a silver film. The fluorescence intensity is
fundamentally affected by the local electromagnetic field enhancement and the quantum yield change according to the
surrounding structure and materials. By utilizing the Fresnel equation and classical dipole radiation modeling, local
electric field enhancement, fluorescence quantum yield, and fluorescence emission coupling yield via SPs were
theoretically analyzed at different dielectric spacer thicknesses between the fluorescence dye and the metal film. The
fluorescence lifetime was also decreased substantially via the quenching effect. A two-photon excited total internal
reflection fluorescence (TIRF) microscopy with a time-correlated single photon counting device has been developed to
measure the fluorescence lifetimes, photostabilities, and enhancements. The experimental results demonstrate that the
fluorescence lifetimes and the trend of the enhancements are consistent with the theoretical analysis. The maximum
fluorescence enhancement factor in the surface plasmon-total internal reflection fluorescence (SP-TIRF) configuration
can be increased up to 30 fold with a suitable thickness SiO<sub>2</sub> spacer. Also, to compromise for the fluorescence
enhancement and the fluorophore photostability, we find that the SP-TIRF configuration with a 10 nm SiO<sub>2</sub> spacer can
provide an enhanced and less photobleached fluorescent signal via the assistance of enhanced local electromagnetic
field and quenched fluorescence lifetime, respectively.
In this manuscript, we report on the successful fabrication of high performance polymer light emitting diodes (PLEDs) using a low temperature, plastic lamination process. Blue- and red-emitting PLEDs were fabricated by laminating different luminescent polymers and organic compounds together to form the active media. This unique approach eliminates the issue of organic solvent compatibility with the organic layers for fabricating multi-layer PLEDs. In addition, a template activated surface process (TAS) has been successfully applied to generate an optimum interface for the low temperature lamination process. The atomic force microscopy analysis reveals a distinct difference in the surfaces created by the TAS and the spin-coating process. This observation coupled with the device data confirms the importance of the activated interface in the lamination process.