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.
We first demonstrated that an organic electroluminescence (EL) device based on conjugated polymers, which emitted polarized light, aligned by ion beam processed films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Such devices would be particularly useful as backlights for conventional LCDs. Homogenous alignment of 4,4'-Bis[2-9(-ethyl-3-carbazoyl)vinylenyl]-1,1'-biphenyl (BECVB) films on thin layers of ion-beam-processed or rubbed PEDOT:PSS allows the construction of light-emitting diodes that emit polarized blue light (λ<sub>em</sub> = 455 nm). The ion-beam-processed or rubbed PEDOT:PSS acts as an effective hole-injecting alignment layer. Polarized photoluminescence spectra demonstrated that the long axis of BECVB molecule was oriented along the ion-beam or rubbing direction. Owing to the orientation of BECVB molecules, polarized EL in the rubbing or ion-beam direction was observed in the device. The maximum photoluminescence polarization ratios of 5.6:1 and 3.2:1 were achieved for the devices aligned by rubbing and ion-beam methods, respectively.