Tungsten oxides as interfacial layers for improved performance in hybrid optoelectronic devices

Kanwat

et al. 2014

Phys. Status Solidi A

We studied the solution processed vanadium pentoxide (V2O5) doping effect in PEDOT:PSS for use in hole injection layer (HIL), and as a result, V2O5 doped PEDOT:PSS improved the performance of polymer light‐emitting diode (PLED) significantly. The improvement is related to the increased conductivity of PEDOT:PSS by V2O5 doping. This improvement enhances hole injection into the emission layer, and it will improve the charge balance. The PLED with PEDOT:PSS HIL and super yellow polymer has maximum current and power efficiencies of 12.01 cd A−1 and 9.67 lm W−1, respectively. On the other hand, the device with V2O5 (10:1) doped PEDOT:PSS indicates the maximum current and power efficiencies of 15.12 cd A−1 and 12.66 lm W−1, respectively, indicating that the efficiencies increase over 20% compared to the control device. The leakage currents of the PLED decrease to ∼10% of the control PLED. Note also that V2O5 suppressed the diffusion of indium from anode to PEDOT:PSS, and also prevented the acidic damage from sulfate ions of PEDOT:PSS to IZO and active layer.

Section: Introductionmentioning

confidence: 99%

Solution processed polymer light emitting diode with vanadium-oxide doped PEDOT:PSS

Kanwat

et al. 2014

Phys. Status Solidi A

“…Attempts to synthesize 1 and 2 by reaction of the commercially available WO 2 Cl 2 with the alkoxide ligands in DME resulted in no product formation, even after refluxing the reaction mixture for several days. The soluble derivative WO 2 Cl 2 (DME) 39 (6) was found to be a more convenient starting material. Upon refluxing a solution of 6 with sodium fluoroalkoxide 7 or 8, the reaction proceeded to afford 1 or 2 through a chloride−alkoxide exchange process (Scheme 1).…”

Section: ■ Introductionmentioning

confidence: 99%

Dioxo–Fluoroalkoxide Tungsten(VI) Complexes for Growth of WO_x Thin Films by Aerosol-Assisted Chemical Vapor Deposition

et al. 2015

The soluble bis(fluoroalkoxide) dioxo tungsten(VI) complexes WO2(OR)2(DME) [1, R = C(CF3)2CH3; 2, R = C(CF3)3] have been synthesized by alkoxide-chloride metathesis and evaluated as precursors for aerosol-assisted chemical vapor deposition (AACVD) of WOx. The (1)H NMR and (19)F NMR spectra of 1 and 2 are consistent with an equilibrium between the dimethoxyethane (DME) complexes 1 and 2 and the solvato complexes WO2(OR)2(CD3CN)2 [1b, R = C(CF3)2CH3; 2b, R = C(CF3)3] in acetonitrile-d3 solution. Studies of the fragmentation of 1 and 2 by mass spectrometry and thermolysis resulted in observation of DME and the corresponding alcohols, with hexafluoroisobutylene also generated from 1. DFT calculations on possible decomposition mechanisms for 1 located pathways for hydrogen abstraction by a terminal oxo to form hexafluoroisobutylene, followed by dimerization of the resulting terminal hydroxide complex and dissociation of the alcohol. AACVD using 1 occurred between 100 and 550 °C and produced both substoichiometric amorphous WOx and a polycrystalline W18O49 monoclinic phase, which exhibits 1-D preferred growth in the [010] direction. The work function (4.9-5.6 eV), mean optical transmittance (39.1-91.1%), conductivity (0.4-2.3 S/cm), and surface roughness (3.4-7.9 nm) of the WOx films are suitable for charge injection layers in organic electronics.

“…These issues illustrate the need for a chemically stable and mechanically uniform material to be used as the HEL to replace PEDOT:PSS in OPVs. Therefore, many attempts have been made using metal oxides, selfassembled monolayers, and p-type polymer blends [9][10][11][12][13][14][15][16][17][18][19].…”

mentioning

confidence: 99%

Graphene oxide/PEDOT:PSS and reduced graphene oxide/PEDOT:PSS hole extraction layers in organic photovoltaic cells

Park

Choi

Physica Status Solidi (a)

2012

A comparison was made between the use of graphene oxide (GO)/poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and reduced graphene oxide (rGO)/PEDOT:PSS as a hole extraction layer (HEL) in organic photovoltaic (OPV) cells. Hydrazine hydrate (HYD) and the thermal method were adopted to change the GO to rGO. The OPV cell with the GO ($2 nm)/PEDOT:PSS HEL exhibits a power conversion efficiency (PCE) as high as 3.53% under 100 mW/cm 2 illumination and air mass conditions, which is higher than that of the OPV cell without the HEL, viz. 1.78%. The device with the PEDOT:PSS/GO HEL shows a similar PCE of 3.48%. However, the PCE of the OPV cell with the rGO/PEDOT:PSS HEL is not high as those of the cells with the HYD-rGO/ PEDOT:PSS and T-rGO/PEDOT:PSS, viz. 3.3 and 3.37%, respectively. The work function of GO was 4.7 eV, but those of HYD-rGO and T-rGO were 4.2 and 4.5 eV, respectively, suggesting that the decrease of the barrier height between GO and active materials is higher than that in rGO case.