PSS Buffer Layer Research Articles

The enhanced properties of amplified spontaneous emission and organic light emitting diodes based on Ag NPs doped hole transfer layer

The organic semiconductor lasers (OSLs) have been seen as a promising light source for future applications. Lower amplified spontaneous emission (ASE) threshold of the organic gain medium and optimized device structures are key factors to realize electrically pumped OSLs. In this paper, the silver nanoparticles (Ag NPs) doped PEDOT: PSS buffer layer was used to improve the ASE performance of BUBD-1 molecule and the optoelectronic performance of the corresponding organic light-emitting diodes (OLEDs). Compared with the reference device with pure PEDOT: PSS buffer layer, the lowest ASE threshold was obtained in CBP: 45 wt%BUBD-1 blend film at the optimal volume ratio 1:3 of PEDOT: PSS: Ag NPs, decreased by 6 times. Then the Ag NPs doped PEDOT: PSS buffer layer was used as both buffer layer and the hole transport layer in the OLEDs devices with CBP: 45 wt% BUBD-1 blend films as the emission layer. At the optimal volume ratio of PEDOT: PSS to Ag NPs, the maximum brightness increased more than 2 times to 7823 cd/m2, and the maximum EQE increased nearly 2 times to 2.81%. The improved ASE performance of CBP: 45 wt%BUBD-1 blend films and optoelectronic properties of corresponding OLED devices can be attributed to both the localized surface plasmon resonance (LSPR) effect and the increased hole mobility caused by the addition of Ag NPs. The introduction of Ag NPs to the hole transfer layer of OLED devices may provide a potential method to realize the electrically pumped OSLs with the planar structures.

Effect of the PEDOT:PSS buffer layer on the performance of hybrid ZnO nanorods/polymer electroluminescent diode

Hybrid ZnO nanorods/polymer light-emitting diodes have excited much attraction because of the combination of high optoelectronic properties of ZnO nanorod with the variety and processability of polymers. In this research, the hybrid ZnO nanorods/polymer heterostructure UV-LED is investigated using ATLAS module of SILVACO TCAD software. In order to observe the influence of PEDOT:PSS hole injection layer/buffer layer in a AZO/ZnO NRs/MEH-PPV heterostructure device, first an ab initio approach have been done on PEDOT:PSS, MEH-PPV and AZO layers. The density of states, electronic band structure and the imaginary part of the dielectric function have been analyzed to deduce the electronic and optic features of the aforesaid layers. In continue, current–voltage characteristics and electroluminescence (EL) spectra of three structures of ITO/MEH-PPV/Al, ITO/ZnO/MEH-PPV/Al and ITO/ZnO/ZnO NR/MEH-PPV/Al have been simulated and compared with the literature experimental works to verify the simulation approach. Moreover, Langevin recombination rate, radiative recombination rate and luminescence power of the mentioned structures have been carefully investigated. Finally, the current–voltage characteristics, luminescence power and EL spectra of the novel proposed devices with the structures of ITO/PEDOT:PSS/AZO/ZnO NR/MEH-PPV/Al and ITO/PEDOT:PSS/ZnO/ZnO NR/MEH-PPV/Al have been investigated. The turn-on voltage of the proposed structure is decreased from 22 to 16 V because of the insertion of the PEDOT:PSS buffer layer and lowering of the hole injection barrier between ITO and ZnO layers. A little blue shift is observed around the wavelength of 380 nm which is attributed to the AZO layer.

The facile modification of PEDOT:PSS buffer layer by polyethyleneglycol and their effects on inverted perovskite solar cell

The effect of polyethyleneglycol-200 (PEG-200) post-treatment on common commercial PEDOT:PSS buffer layer for perovskite solar cell has been carefully investigated. Through facile annealing post-treatment of PEG/PEDOT:PSS film at 120 °C for 10 min, the conversion efficiency of the cells can be enhanced 7.5% (11.68% to 12.56%) compared to the traditional inverted perovskite solar cell, with the improvement of both short-circuit current density and fill factor. Our results indicate that the treatment by PEG on PEDOT:PSS film is an effective way to improve perovskite solar cell efficiency. In addition, it reveals that the PEG-200 can greatly enhance not only the conductivity but also improve the buffer layer morphology or PEDOT:PSS polymer chain packing. Furthermore, the devices impedance spectroscopy reveals that the PEG post treatment would decrease Rct drastically, suggesting the improvement of contact interface between PEDOT:PSS and perovskite layer.

Inverted Polymer Solar Cells with a Reduced Graphene Oxide/Poly (3,4-Ethylene Dioxythiophene):Poly(4-Styrene Sulfonate) (PEDOT:PSS) Hole Transport Layer

In this study, high-efficiency inverted polymer solar cells were developed by using graphene oxide/poly(3,4-ethylene-dioxythiophene):poly(4-styrene-sulfonate) (GO/PEDOT:PSS) composites films acting as hole transport layer into the device structure based on Indium Tin Oxide (ITO)/Zinc Oxide (ZnO)/Poly(3-hexylthiophene):[6,6]phenyl-C61-butyric Acid Methyl Ester (P3HT:PCBM)/GO:PEDOT:PSS/Silver (Ag). The electrical conductivity and Seebeck coefficient of the films have been measured at room temperature and a maximum of conductivity achieved was for 492 S/cm for a 3 wt.% GO/PEDOT:PSS film treated with dimethyl sulfoxide as solvent and a decrease in the conductivity was observed for higher content of GO even after chemical or thermal reduction. The energy conversion efficiency was enhanced from 2.14% to 3.06% by incorporating 3 wt.% of GO into the PEDOT:PSS buffer layer. Thus, the 3 wt.% GO/PEDOT:PSS is a promising buffer layer for photovoltaic and electronic applications, since a decrease of the overall performance of the photovoltaic device was observed for higher concentration of GO.

Improved Performance of Organic Star-Shaped Molecule Solar Cells with SiO2 Nanoparticles Embedded in a Buffer Layer

We have studied the effect of spherical SiO2 nanoparticles with sizes of 20, 50, and 80 nm embedded in a PEDOT : PSS buffer layer on the performance of organic solar cells (OSCs) based on star-shaped oligomers. The current–voltage characteristics and absorption spectra of samples have been measured and analyzed; the morphology of the buffer layer surface with embedded nanoparticles has been studied. It has been shown that an increase in the OSC performance occurs in the case of embedded nanoparticles with a diameter of 20 and 50 nm and weakly depends on the concentration of the nanoparticles in the layer.

D-π-A-π-D type thiazolo[5,4-d]thiazole-core organic chromophore and graphene modified PEDOT:PSS buffer layer for efficient bulk heterojunction organic solar cells

A new thiazolo[5,4-d]thiazole-core organic chromophore with furan spacer (TP-FTzF-TP) was synthesized and PEDOT:PSS buffer layer was modified by graphene (Gr) for the efficient solution-processed bulk-heterojunction (BHJ) small molecule organic solar cells (SMOSCs). The introduction of furan as spacer in the thiazolo[5,4-d]thiazole-core based organic chromophore tuned the absorption and the electrochemical properties. The synthesized TP-FTzF-TP chromophore exhibited good optical parameters and a suitable HOMO/LUMO values of −5.33 eV/−3.15 eV. The synthesized organic chromophore with triphenylamine as a strong electron-donor and furan spacer promoted the charge transfer and charge extraction in fabricated SMOSCs. The modification of PEDOT:PSS by Gr considerably increased the roughness of thin film. The power conversion efficiency (PCE) of ∼3.63% was achieved by fabricated SMOSC device with ITO/Gr-PEDOT:PSS/TP-FTzF-TP:PC60BM (1:2, w/w)/Au architecture. It was found that the Gr-PEDOT:PSS as a buffer layer significantly enhanced PCE by two time factor as compared to the SMOSC device (PCE = ∼2.13%) with pristine PEDOT:PSS layer.

The effects of solvent treated PEDOT:PSS buffer layer in organic solar cells

Various treatments on the PEDOT:PSS films were carried out to investigate it’s influence on the conductivity, morphology, transmittance and the corresponding impact of the performance of the organic photovoltaic devices based on the PCPDTBT:PCBM and P3HT:PCBM blends. These processing including doping PEDOT:PSS with DMF and ME solvents and exposing these films to the vapor of DMF and ME solvents, separately. A considerable enhancement of the conductivity and transmittance of PEDOT:PSS was observed after doping solvent into the PEDOT;PSS solution followed by solvent treatment through exposing these films to solvents environment. The best organic PV doped devices based on either PCPDTBT:PCBM or based on P3HT:PCBM with power conversion efficiency were 2.93% compared to 1.87% for the pristine PV devices or 2.79% compared to 1.77% for the pristine devices, respectively. The conductivity improvement was highly influenced by solvent treatment.

Enhancing Optically Pumped Organic-Inorganic Hybrid Perovskite Amplified Spontaneous Emission via Compound Surface Plasmon Resonance

Organic-inorganic hybrid perovskite has attracted intensive attention from researchers as the gain medium in lasing devices. However, achieving electrically driven lasing remains a significant challenge. Modifying the devices’ structure to enhance the optically pumped amplified spontaneous emission (ASE) is the key issue. In this work, gold nanoparticles (Au NPs) are first doped into PEDOT: PSS buffer layer in a slab waveguide device structure: Quartz/PEDOT: PSS (with or w/o Au NPs)/CH3NH3PbBr3. As a result, the facile device shows a significantly enhanced ASE intensity and a narrowed full width at half maximum. Based on experiments and theoretical simulation data, the improvement is mainly a result of the compound surface plasmon resonance, including simultaneous near- and far-field effects, both of which could increase the density of excitons excited state and accelerate the radiative decay process. This method is highly significant for the design and development and fabrication of high-performance organic-inorganic hybrid perovskite lasing diodes.

Improved efficiency of organic solar cells using Au NPs incorporated into PEDOT:PSS buffer layer

Au based plasmonic phenomenon inside the hole transport layer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) of an organic solar cell based on blend of poly(3-hexylthiophene) (P3HT) and [6:6]-phenyl-C61-butyric acid (PCBM) is investigated. The concentration of the Au nanoparticles synthesized by wet chemical reduction is one of the key factors to strong light trapping when the spherical gold nanoparticles are blended into the PEDOT:PSS solution. Studies of the influence of the concentration of nanoparticles distribution in the PEDOT:PSS were carried out using UV–Vis spectroscopy and atomic force microscopy. Electrical characteristics of the pristine device and of device with metallic nanostructures were analyzed from J –V characteristics to observe the plasmonic effects on the performance in the P3HT:PCBM organic solar cells. The origin of the photocurrent enhancements with varying Au nanoparticles concentrations on PEDOT:PSS are discussed.

Functional solid additive modified PEDOT:PSS as an anode buffer layer for enhanced photovoltaic performance and stability in polymer solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is most commonly used as an anode buffer layer in bulk-heterojunction (BHJ) polymer solar cells (PSCs). However, its hygroscopic and acidic nature contributes to the insufficient electrical conductivity, air stability and restricted photovoltaic (PV) performance for the fabricated PSCs. In this study, a new multifunctional additive, 2,3-dihydroxypyridine (DOH), has been used in the PEDOT: PSS buffer layer to obtain modified properties for PEDOT: PSS@DOH and achieve high PV performances. The electrical conductivity of PEDOT:PSS@DOH films was markedly improved compared with that of PEDOT:PSS. The PEDOT:PSS@DOH film exhibited excellent optical characteristics, appropriate work function alignment, and good surface properties in BHJ-PSCs. When a poly(3-hexylthiohpene):[6,6]-phenyl C61-butyric acid methyl ester blend system was applied as the photoactive layer, the power conversion efficiency of the resulting PSCs with PEDOT:PSS@DOH(1.0%) reached 3.49%, outperforming pristine PEDOT:PSS, exhibiting a power conversion enhancement of 20%. The device fabricated using PEDOT:PSS@DOH (1.0 wt%) also exhibited improved thermal and air stability. Our results also confirm that DOH, a basic pyridine derivative, facilitates adequate hydrogen bonding interactions with the sulfonic acid groups of PSS, induces the conformational transformation of PEDOT chains and contributes to the phase separation between PEDOT and PSS chains.

Large area flexible polymer solar cells with high efficiency enabled by imprinted Ag grid and modified buffer layer

To take a full advantage of polymer semiconductors on realization of large-area flexible photovoltaic devices, herein, we fabricate polymer solar cells on the basis of polyethylene terephthalate (PET) with imprinted Ag grid as transparent electrode. The key fabrication procedure is the adoption of a modified PEDOT:PSS (PH1000) solution for spin-coating the buffer layer to form a compact contact with the substrate. In comparison with the devices with intrinsic PEDOT:PSS buffer layer, the advanced devices present a much higher efficiency of 6.51%, even in a large device area of 2.25 cm2. Subsequent characterizations reveal that such devices show an impressive performance stability as the bending angle is enlarged to 180° and bending time is up to 1000 cycles. Not only providing a general methodology to construct high efficient and flexible polymer solar cells, this paper also involves deep insights on device working mechanism in bending conditions.

Flexible nonvolatile memory devices based on Au/PMMA nanocomposites deposited on PEDOT:PSS/Ag nanowire hybrid electrodes

Flexible nonvolatile memory (NVM) devices fabricated utilizing Au nanoparticles (AuNPs) embedded in a poly(methylmethacrylate) (PMMA) layer were fabricated on a silver nanowire (AgNW) or a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/AgNW coated on poly(ethylene terephthalate) (PET) substrates. The transmittance and the sheet resistance of the PEDOT:PSS/AgNW hybrid layer were approximately 89% and 50Ω/sq, respectively, which were comparable to the values for commercial indium-tin-oxide (ITO) electrodes. Current-voltage curves for the Al/PMMA:AuNP/PEDOT:PSS/AgNW/PET devices at 300K showed clockwise current hysteresis behaviors due to the existence of the AuNPs. The endurance number of ON/OFF switching for the NVM devices was above 30 cycles. An ON/OFF ratio of 1×103 was maintained for retention times longer than 1×104s. The maximum memory margins of the NVM devices before and after bending were approximately 3.4×103 and 1.4×103, respectively. The retention times of the devices before and after bending remained same 1×104s. The memory margin and the stability of flexible NVMs fabricated on AgNW electrodes were enhanced due to the embedded PEDOT:PSS buffer layer.

Efficiency Enhancement of TiO2 Nanosponge/Spin-Coated P3HT Solar Cells Through the Use of Umbelliferone

Background: Polymeric solar cells (PSC) are advantageous over silicon-based photovoltaic devices in many ways, such as mechanical flexibility and low cost of production, butthe low power conversion efficiency (PCE) of PSCs and their relatively small lifetimes due to polymer degradation when exposed to UV radiation constitute considerable disadvantages. The aim of this paper is to enhance the PCE of the produced TiO2 nanosponge/spin-coated P3HT solar cells by doping of the PEDOT:PSS buffer layer with the coumarin known as umbelliferone. Methods: Devices were produced by spin-coating a P3HT layer over an electrochemically grown TiO2 nanostructured thin film. The PEDOT:PSS buffer layer having umbelliferone as an additive was deposited over the P3HT layer using air spray technique. Finally, the samples were thermally treated by annealing at 180°C. Result: The buffer layer, where the PEDOT:PSS layer was doped by umbelliferone, was characterized by NMR, MEV and conductivity measurements. It was observed that the conversion efficiency is enhanced for devices containing umbelliferone in the buffer layer, and the best result indicated a conversion efficiency of around 1.65%, with open circuit voltages and short circuit current as high as 320mV and 0.180mA, respectively, for devices with effective area of around 1mm2. Conclusion: It was observed that the conversion efficiencies of the umbelliferone additivate devices were almost twice as large as the non-additivated devices. The physical reason for the PCE enhancement is associated with chemical bond between umbelliferone molecules and PSS ionomers, producing a conductivity increase and morphological effects on the buffer layer. Keywords: P3HT, polymer solar cells, TiO2 nanosponge, umbelliferone.

Improvement of organic solar cells using aluminium microstructures prepared in PEDOT:PSS buffer layer by using ultrasonic ablation technique

In the present work we introduce an improvement of organic solar cell efficiency by using aluminium microstructures (Al MSs) dispersed in poly(3,4-ethylene dioxythiophene)-blend-poly(styrene sulfonate) (PEDOT:PSS) buffer layer. Al microstars (in the range of 5–16μm) in addition to Al nanoparticles (Al NPs) have been prepared by new ultrasonic ablation technique through the application of ultrasonic irradiation upon Al thin film immersed in PEDOT:PSS solution. In the beginning, we found that the PEDOT:PSS solution completely dissolves Al thin film before the applying of ultrasonic irradiation as a result of acidic nature of the PEDOT:PSS solution. The action of PEDOT:PSS on the Al film tends to produce Al microcircles, which are dissociated into Al microstars after the applying of ultrasonic irradiation. The short circuit current density, fill factor, and, consequently, power conversion efficiency of the investigated solar cells have been improved by the incorporation of Al microstars, which can facilitate the transport of charge carriers, specifically holes, to be transferred along the axis of the Al microstars in the buffer layer of the solar cell. We found that the increase in ultrasonication time applied upon the solution of PEDOT:PSS-Al microstars diminishes the length of Al microstars and reduces the number of Al microstars' arms. Therefore, further increase in the ultrasonication time tends to decrease the device performance parameters due to the deficit of charge carriers to be transferred in the buffer layer matrix. The Al microstars prepared by ultrasonic ablation technique are pure and free of surfactants and passivation layers that are inevitably present on the surface of the chemically synthesized metal MSs and NPs. The new ultrasonic ablation method is safe (different than laser ablation technique) to prepare metal NPs and MSs in the sensitive organic solvents and solutions which are directly used to prepare organic solar cells. In addition, the new technique enables us to prepare desirable size of Al microstars, which can be suitable for improving organic solar cells and in other different applications.

Stability enhancement in organic solar cells by incorporating V2O5nanoparticles in the hole transport layer

The synthesis of vanadium pentaoxide (V2O5) nanoparticles by a hydrothermal method and their utilization in a PEDOT:PSS buffer layer in a PCDTBT:PC71BM device structure is demonstrated.

Improving the performance of perovskite solar cells with glycerol-doped PEDOT:PSS buffer layer**Project supported by the National Natural Science Foundation of China (Grant Nos. 61264002, 61166002, 91333206, and 51463011), the Natural Science Foundation of Gansu Province, China (Grant No. 1308RJZA159), the New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-13-0840), the Research Project of Graduate

In this paper, we investigate the effects of glycerol doping on transmittance, conductivity and surface morphology of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)) (PEDOT:PSS) and its influence on the performance of perovskite solar cells. . The conductivity of PEDOT:PSS is improved obviously by doping glycerol. The maximum of the conductivity is 0.89 S/cm when the doping concentration reaches 6 wt%, which increases about 127 times compared with undoped. The perovskite solar cells are fabricated with a configuration of indium tin oxide (ITO)/PEDOT:PSS/CH3NH3PbI3/PC61BM/Al, where PEDOT:PSS and PC61BM are used as hole and electron transport layers, respectively. The results show an improvement of hole charge transport as well as an increase of short-circuit current density and a reduction of series resistance, owing to the higher conductivity of the doped PEDOT:PSS. Consequently, it improves the whole performance of perovskite solar cell. The power conversion efficiency (PCE) of the device is improved from 8.57% to 11.03% under AM 1.5 G (100 mW/cm2 illumination) after the buffer layer has been modified.

Simultaneous enhancement of the efficiency and stability of organic solar cells using PEDOT:PSS grafted with a PEGME buffer layer

We report a simple processing method to simultaneously improve the efficiency and stability of organic solar cells (OSCs). Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxy-thiophene (PEDOT:PSS), widely used as hole transport layer (HTL) in OSCs, tends to accelerate the degradation of devices because of its hygroscopic and acidic properties. In this regard, we have modified PEDOT:PSS to reduce its hygroscopic and acidic properties through a condensation reaction between PEDOT:PSS and poly(ethylene glycol) methyl ether (PEGME) in order to improve the efficiency and stability of OSCs. As a result, the power conversion efficiency (PCE) increased by 21%, from 2.57% up to 3.11%. A better energy level alignment by the reduced work function of the modified PEDOT:PSS with a highest occupied molecular orbital (HOMO) level of poly(3-hexylthiophene-2,5-diyl) (P3HT) is considered the origin of the improved the efficiency. The half-life of OSCs with PEDOT:PSS modified with PEGME buffer layer also increased up to 3.5 times compared to that of devices with pristine PEDOT:PSS buffer layer.

Work function and interface control of amorphous IZO electrodes by MoO3 layer grading for organic solar cells

To control the work function and the interface of transparent anodes for use in organic solar cells (OSCs), we fabricated an amorphous Zn-doped In2O3 (IZO) films with graded MoO3 top layers by using a graded sputtering technique. Electrical, optical, structural, and morphological properties of the MoO3 graded IZO films (MIZO) were investigated in detail by studying MIZO films with various thickness of the MoO3 graded layer. Graded sputtering of the MoO3 layer on the top region of IZO films led to the high work function of 5.23eV for the amorphous IZO, which was higher than that of the MoO3/IZO double layer, even though MIZO had resistivity similar to that of the IZO single layer. Due to the high work function and high transparency of the MIZO films, OSCs based on the MIZO anode exhibited a power conversion efficiency (PCE) of 3.2%, greater than that of OSCs based on IZO single layer and MoO3/IZO double layer anodes. Based on Kelvin probe measurements and transmission electron microscope examinations, we suggested a possible hole extraction mechanism at the interfaces between the MIZO anode and the PEDOT:PSS buffer layer to explain the higher PCE of OSCs based on MIZO anodes. The successful operation of OSCs on graded MIZO indicated that the graded sputtering technique is a promising coating process allowing modification of surface properties of amorphous IZO anodes without requiring additional solution coating processes.

Effects of PTFE and PEDOT:PSS Double Buffer Layers on Flexible Polymer Solar Cells

We investigate the effects of polytetrafluoroethylene (PTFE) on organic photovoltaic (OPV) devices with structure of ITO/PTFE/PEDOT:PSS/P3HT:PCBM/PTFE/Al by inserting thermally evaporated PTFE films between indium-tin-oxide (ITO) and PEDOT:PSS layers, and also between P3HT:PCBM and Al, respectively. Significant improvement in terms of open-circuit voltage, Fill factor (FF), and thereby in its commensurate power conversion efficiency is achieved compared to devices with PEDOT:PSS and LiF buffer layers. The OPVs performance enhancement is attributed to the formation of an artificial dipole layer resulting from the rich, negatively charged fluorine that facilitates the charge extraction process.

Efficient and stable polymer solar cells with annealing-free solution-processible NiO nanoparticles as anode buffer layers

Annealing-free solution-processible nickel oxide (NiO) nanoparticles are prepared via sonochemical synthesis. In contrast to the common sol–gel route to prepare a NiOx film that had to undergo high-temperature post-annealing to be converted into NiO nanoparticles, herein, colloidal crystalline NiO nanoparticles with diameters of 4–8 nm are prepared with the metal salt at low temperature via ultrasonic irradiation. The colloidal crystalline NiO nanoparticles were directly used as the anode buffer layer in polymer solar cells (PSCs) without post-thermal annealing, which was compatible with flexible substrates and low-cost high-throughput fabrication. After O2-plasma treatment to the as-deposited buffer layer of NiO nanoparticles, the ITO/NiO contact work function was increased from −4.8 to −5.3 eV, providing superior contact with the highest occupied molecular orbital energy levels of polymer donors. Compared to PCDTBT:PC70BM PSCs with a PEDOT:PSS buffer layer, the power conversion efficiency of PSCs with an O2-plasma treated anode buffer layer of NiO nanoparticles was increased from 5.84% to 6.30% and the device stability was also enhanced.