Anode Buffer Research Articles

Copper iodide-PEDOT:PSS double hole transport layers for improved efficiency and stability in perovskite solar cells

The hole transport layer (HTL) plays an important role in perovskite solar cells (PSCs). We demonstrate the cupper iodide (CuI)/poly (3,4-ethylenedioxythiophene) poly (styrenesulphonate) (PEDOT:PSS) double layers as the anode buffer layer for efficient hole transport in PSCs. An obvious enhancement of open-circuit voltage and power conversion efficiency (PCE) is observed, and a final PCE of 14.3% is achieved. While the single PEDOT:PSS based device’s PCE is 12.9%. The inorganic CuI buffer layer significantly enhanced the hole extraction from the perovskite film, as revealed from the photoluminescence spectra. The average exciton lifetime is reduced to 2.7 ns. Moreover, the devices with double HTLs structure exhibit better long time stability. The PCE remains 88% of the initial value after 720 h’ storage.

Electrochemical deposition of poly[ethylene-dioxythiophene] (PEDOT) films on ITO electrodes for organic photovoltaic cells: control of morphology, thickness, and electronic properties

In this article, controlled changes on morphology, thickness, and band gap of poly[ethylenedioxythiophene] (PEDOT) polymer films fabricated by electrochemical polymerization (potentiostatically) are analyzed. Electropolymerization of the monomer ethylenedioxythiophene (EDOT) was carried out on indium tin oxide (ITO) electrodes, in different dry organic electrolytic media, such as acetonitrile, acetonitrile–dichloromethane, and toluene–acetonitrile mixtures. It was found that electropolymerization kinetics can be controlled by changing the polarity of the electrolytic media, and kinetics is slower for those with low polarity. This fact combined with an accurate control of EDOT monomer concentration and electropolymerization at Epeak/2 potential, allows to control the morphology and thickness of the electropolymerized PEDOT films (E-PEDOT:ClO4); toluene/ACN (4:1, v/v) and [EDOT] = 0.3 mM gave the best films for application in organic photovoltaic (OPV) cells. The performance of the E-PEDOT:ClO4 films was tested on ITO electrodes as anode buffer layer in OPV cells with the configuration ITO/E-PEDOT:ClO4/P3HT:PC61BM/Field’s metal, where Field’s metal (cathode) is a eutectic alloy that lets to fabricate OPV devices easily and in a fast and economical way at free vacuum conditions. The performance of these devices was compared with an OPV device constructed with a buffer layer anode, prepared using the classical spin coating of PEDOT:PSS on ITO. Results showed that OPV cells fabricated with E-PEDOT:ClO4 have a slightly increased PV performance.

Enhanced device efficiency in organic light-emitting diodes by dual oxide buffer layer

Abstract We have demonstrated an improvement in device performance of fluorescent organic light-emitting diodes (OLEDs) by inserting a dual anode buffer layer composed of tungsten oxide (WO3) and molybdenum oxide (MoO3). The advantage of adding dual anode buffer layers with different deposition sequences over individual and composite oxide buffer layers has been systematically analyzed based on their electronic and optical properties. The incorporation of single and composite buffer layers has been revealed to induce a very low injection barrier for holes in tri-layer fluorescent OLEDs which results in a charge imbalance in the emission layer. In contrast, a proper sequence of buffer layers (WO3/MoO3) exhibiting higher contact angle (lower surface energy) and higher surface roughness, together with a step-wise increment of potential barrier leads to a better overall charge balance in the active emission layer. Therefore, an enhanced current efficiency and power efficiency of ∼5.8 cd/A and ∼5.2 lm/W respectively were recorded for the WO3/MoO3 buffer unit, which was better than the insertion of individual and composite layers.

Effects of Buffer Layer Treatments on the Characteristics and Performances of OLEDs

The authors demonstrated the performance of Organic Light Emitting Diodes (OLEDs) with hexylphosphonic acid (PA) or UV-ozone treatment on their molybdenum trioxide (MoO3) anode buffer layers. The OLEDs with a PA treated (5 mM @1 h) MoO3 layer have lower turn-on voltage and low current efficiency roll-off under high operating current. The hole-only device (ITO/MoO3 with PA or UV-ozone treatment/NPB/Al) was fabricated to calculate the active energy via temperature dependent I-V measurement. When the devices were operated at high temperatures, the activation energy of the UV-ozone treated, and untreated hole-only devices became nonlinear. However, the activation energy of the PA treated devices had a more stable performance at high temperatures. The interfacial resistance of the untreated hole-only devices and the PA and UV-ozone treated devices were calculated by Admittance Spectroscopy (AS) to be 204.5, 363, and 450 Ω. These results indicated that the PA treated devices reduced the activation energy, surface energy mismatch, and interface resistance to enhance the efficiency of carrier injection, which in turn lowers the turn on voltage. Moreover, PA treatment produces a long carbon chain and smooths the morphology of MoO3 to prevent roll-off phenomenon of OLEDs under high operating current.

Enhanced performance of inverted polymer solar cell based on Al2O3/MoO3 as composite anode buffer layer

Inverted polymer solar cell with P3HT:PC61BM as an active layer is fabricated based on Al2O3/MoO3 composite anode buffer layer. Effects of Al2O3/MoO3 composite anode buffer layers with the Al2O3 precursor solutions of different concentrations on the device performance are investigated. It can be found that the Al2O3/MoO3 composite anode buffer layer can effectively enhance the photovoltaic performance and device stability of inverted polymer solar cell. The open-circuit voltage (Voc), short-circuit current (Jsc), filling factor (FF), and photoelectric conversion efficiency (PCE) are 0.64 V, 8.62 mA/cm2, 63.86%, and 3.85% respectively for the control device with MoO3 single buffer layer. In addition, with the increase of the concentration of Al2O3 precursor solution, the photovoltaic performance of the inverted polymer solar cell with Al2O3/MoO3 composite anode buffer layer is gradually improved. For the Al2O3 precursor solution of 0.15%, the photovoltaic performance of the device reaches an optimal value, and the corresponding Voc, Jsc, FF, and PCE are 0.65 V, 11.04 mA/cm2, 64.46%, and 4.64%, respectively. The Jsc and PCE significantly increase by 28% and 20%, respectively, compared with those of the control device with MoO3 single buffer layer. Moreover, after 80 days of measuring the device lifetime, the PCE of the device with the composite anode buffer layer remains at 76% of the original value while the PCE with the single buffer layer is reduced below 50%. The improvement of the device performance should be attributed to the PC61BM receptor near the anode dissolved and washed by isopropyl alcohol solvent from the Al2O3 precursor solution. At the same time, a large number of pits on the surface of the active layer are filled with Al2O3 to make it more smoothly contact the composite anode buffer layer. Therefore, the contact resistance between the active layer and the anode decreases, which enhances hole collection performance of the anode. Simultaneously, the Al2O3 layer can passivate the active layer of the device, thus improving the photovoltaic performance and device stability of inverted polymer solar cell.

Green solvent processed tetramethyl-substituted aluminum phthalocyanine thin films as anode buffer layers in organic light-emitting diodes

Green solvent processable tetramethyl-substituted Al(iii) phthalocyanines were employed as anodic buffer layers of OLEDs, achieving the enhanced OLED performance and durability compared with those of OLEDs using PEDOT:PSS.

采用MoO3阳极缓冲层的钙钛矿太阳能电池研究

采用MoO₃阳极缓冲层的钙钛矿太阳能电池研究

Водорастворимый комплекс полианилина для формирования оптоэлектронных устройств методом струйной печати

AbstractThe influence of the ratio of components in polyaniline (PANI) complexes with poly(sulfonic acid) on the viscosity of their aqueous solutions and electric conductivity of layers formed thereof. The optical properties and morphology of PANI complex layers formed by ink-jet printing have been studied. The optimum ratio of components to be used in anodic buffer layers for organic solar cells is determined.

Fully Coated Semitransparent Organic Solar Cells with a Doctor-Blade-Coated Composite Anode Buffer Layer of Phosphomolybdic Acid and PEDOT:PSS and a Spray-Coated Silver Nanowire Top Electrode.

In the aim to realize high performance semitransparent fully coated organic solar cells, printable electrode buffer layers and top electrodes are two important key technologies. An ideal ink for the preparation of the electrode buffer layer for printed top electrodes should have good wettability and negligible solvent corrosion to the underlying layer. This work reports a novel organic-inorganic composite of phosphomolybdic acid (PMA) and PEDOT:PSS that features excellent wettability with the active layer and printed top Ag nanowires and high resistibility to solvent corrosion. This composite buffer layer can be easily deposited on a polymer surface to form a smooth, homogeneous film via spin-coating or doctor-blade coating. Through the use of this composite anode buffer layer, fully coated semitransparent devices with doctor-blade-coated functional layers and spray-coated Ag nanowire top electrodes showed the highest power conversion efficiency (PCE) of 5.01% with an excellent average visible-light transmittance (AVT) of 50.3%, demonstrating superior overall characteristics with a comparable performance to and a much higher AVT than cells based on a thermally evaporated MoO3/Ag/MoO3 thin film electrode (with a PCE of 5.77% and AVT of 19.5%). The current work reports the fabrication of fully coated inverted organic solar cells by combining doctor-blade coating and spray coating and, more importantly, demonstrates that a nanocomposite of a polyoxometalate and conjugated polymer could be an excellent anode buffer layer for the fully coated polymer solar cells with favorable interfacial contact, hole extraction efficiency, and high comparability with full printing.

Efficient and Stable Pure Green All-Inorganic Perovskite CsPbBr3 Light-Emitting Diodes with a Solution-Processed NiOx Interlayer

The perovskite-based optoelectronic applications always suffer from stability issues, due to the intrinsic chemical instability of the perovskite materials. Besides, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is always utilized as an anode buffer layer in thin-film perovskite light-emitting diodes (PeLEDs), which may lead to stability issues due to the hygroscopic and acidic nature of PEDOT:PSS. In this paper, inorganic metal oxide NiOx is employed as a hole injection layer (HIL) and hole transport layer (HTL) to substitute detrimental PEDOT:PSS in all-inorganic PeLEDs. Then fully covered CsPbBr3 polycrystalline films are fabricated by using a one-step spin-coating method based on nonstoichiometric and polymer-assisted perovskite precursor solutions. The optimized films not only have compact morphology but also have excellent photoluminescence quantum yield (PLQY). Encouragingly, by introducing a metal oxide NiOx, the CsPbBr3 PeLEDs show a maximum luminance of 23 828 cd m–2 and maxi...

Solution processed transition metal oxide anode buffer layers for efficiency and stability enhancement of polymer solar cells

Polymer solar cells were fabricated with solution-processed transition metal oxides, MoO3 and V2O5 as anode buffer layers (ABLs). The optimized device with V2O5 ABL exhibited considerably higher power conversion efficiency (PCE) compared to the devices based on MoO3 and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) ABLs. The space charge limited current measurements and impedance spectroscopy results of hole-only devices revealed that V2O5 provided a very low charge transfer resistance and high hole mobility, facilitating efficient hole transfer from the active layer to the ITO anode. More importantly, incorporation of V2O5 as ABL resulted in substantial improvement in device stability compared to MoO3 and PEDOT:PSS based devices. Unencapsulated PEDOT:PSS-based devices stored at a relative humidity of 45% have shown complete failure within 96 h. Whereas, MoO3 and V2O5 based devices stored in similar conditions retained 22% and 80% of their initial PCEs after 96 h. Significantly higher stability of the V2O5-based device is ascribed to the reduction in degradation of the anode/active layer interface, as evident from the electrical measurements.

Stability enhancement of P3HT:PCBM polymer solar cells using thermally evaporated MoO3 anode buffer layer

Polymer solar cells have been fabricated with thermally evaporated MoO3 as anode buffer layer (ABL). The stability of MoO3 and PEDOT:PSS based devices was examined under different test conditions. The MoO3 based device exhibited a slightly better efficiency and significantly higher stability compared to PEDOT:PSS based device. At a relative humidity of 45% the unencapsulated PEDOT:PSS based device degraded completely within 96 h. On the other hand, MoO3 based device retained more than 60% of its initial efficiency after 96 h. The reason behind stability enhancement was investigated by measuring time-evolution of reflectance and hole-current. Experimental results revealed that the stability enhancement for MoO3 based device originates from the reduction in degradation of anode/active layer interface.

Bright prospect of using alcohol-soluble Nb2O5 as anode buffer layer for efficient polymer solar cells based on fullerene and non-fullerene acceptors

New breakthroughs are expecting to be achieved based on the discovery of novel interfacial materials for polymer solar cells (PSCs). Herein, the simple and facial approach of spin-coating technology with post heat and ultraviolet-ozone treatment is performed on niobium oxalate to prepare Nb2O5 interfacial layer with ultra-high transmittance. The ultraviolet photoemission spectroscopy results confirm that Nb2O5 with a work function of 4.85 eV is suitable for employing as anode buffer layer (ABL). The average power conversion efficiencies (PCEs) of the P3HT:PCBM-based fullerene devices with Nb2O5 ABL reaches to 4.01%, surpassing that (3.69%) of the control devices with ITO/PEDOT:PSS ABL. Further investigations on the PBDB-T:ITIC-based non-fullerene PSCs with Nb2O5 ABL demonstrate that a PCE as high as 8.67% can be reached, which is superior to that of device modified by PEDOT:PSS ABL (8.03%). Namely, 8% efficiency improvement in PSCs based on fullerene and non-fullerene acceptors realized as compared to the control devices with PEDOT:PSS ABL.

The Effect of Donor and Nonfullerene Acceptor Inhomogeneous Distribution within the Photoactive Layer on the Performance of Polymer Solar Cells with Different Device Structures.

Due to the inhomogeneous distribution of donor and acceptor materials within the photoactive layer of bulk heterojunction organic solar cells (OSCs), proper selection of a conventional or an inverted device structure is crucial for effective exciton dissociation and charge transportation. Herein, we investigate the donor and acceptor distribution within the non-fullerene photoactive layer based on PBDTTT-ET:IEICO by time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) and scanning Kelvin probe microscopy (SKPM), indicating that more IEICO enriches on the surface of the photoactive layer while PBDTTT-ET distributes homogeneously within the photoactive layer. To further understand the effect of the inhomogeneous component distribution on the photovoltaic performance, both conventional and inverted OSCs were fabricated. As a result, the conventional device shows a power conversion efficiency (PCE) of 8.83% which is 41% higher than that of inverted one (6.26%). Eventually, we employed nickel oxide (NiOx) instead of PEDOT:PSS as anode buffer layer to further enhance the stability and PCE of OSCs with conventional structure, and a promising PCE of 9.12% is achieved.

Polymer-assisted deposition of SrTiO3 film as cathode buffer layer in inverted polymer solar cells

Polymer-assisted deposition (PAD) method has been employed to prepare SrTiO3(STO) films on ITO substrates, which have been applied as cathode buffer layer in inverted polymer solar cells. ZnO and TiO2 films on ITO glass were also prepared via PAD and have been utilized as cathode buffer layers in the inverted polymer solar cells for comparison, which show better efficiency than those using ZnO and TiO2 as interfacial layers prepared through other methods. The power conversion efficiency (PCE) of ∼3.5% was achieved with STO as the cathode buffer layer as well as MoO3 as the anode buffer layer, which is comparable to that with ZnO and TiO2 prepared using the same method as cathode buffer layers. Our findings indicate that STO has the potential to be a candidate as interfacial layers in solar cell devices.

Improved photocurrent of PDPP3T based organic Schottky junctions via solution-processed HAT-CN and TPBi as anode and cathode buffer layers (Phys. Status Solidi A 9∕2017)

Improved photocurrent of PDPP3T based organic Schottky junctions via solution-processed HAT-CN and TPBi as anode and cathode buffer layers (Phys. Status Solidi A 9∕2017)

Mo(SxOy) thin films deposited by electrochemistry for application in organic photovoltaic cells

In this study, Mo(SxOy) thin films were deposited onto fluorine doped tin oxide (FTO) using pulsed electrochemical deposition method. It is shown by scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy that after water cleaning the deposited Mo(SxOy) film corresponds to a hybrid layer MoSx:MoO3. This hybrid is used as anode buffer layer (ABL) in planar organic photovoltaic cells (OPVCs) based on the couple copper-phthalocyanine/fullerene. It is shown that it is necessary to proceed to a soft annealing-5 min at 150 °C- of the anode FTO/Mo(SxOy) to clean the ABL surface in order to obtain efficient contact with the organic material. The OPVC with the optimum Mo(SxOy) thickness, 12 nm, showed a power conversion efficiency, PCE = 1.41% under an illumination of AM1.5, which is 12% higher than that achieved with a simple MoO3 ABL. This improvement is attributed to the fact that using a hybrid MoS2:MoO3 ABL allows to combine the advantages of its both constituents. The MoSx blocks the electrons, while the high work function of MoO3 induces a high hole extraction efficiency at the interface electron donor/anode.

Improved performance for polymer solar cells using CTAB-modified MoO3 as an anode buffer layer

We report a method to prepare molybdenum oxide thin films using the stable cetrimonium bromide-modified MoO3 (CTAB-modified MoO3) precursor solution. The effect of thermal treatment on the optical, crystalline, morphologic properties and surface wettability is greatly obvious because of the pyrolytic decomposition of CTAB. The highly efficient and stable polymer solar cells (PSCs) have been also fabricated by adopting CTAB-modified MoO3 nanocomposite films as the novel and universal anode buffer layers (ABLs). The P3HT:ICBA based solar cells with CTAB-modified MoO3 at 200°C heat treatment exhibit an best power conversion efficiency (PCE) of 5.80% with long-term stability, and the PTB7:PC71BM based solar cells with CTAB-modified MoO3 at 200°C heat treatment show an best PCE of 8.34% with long-term stability, which are higher than that of the corresponding devices with PEDOT:PSS films. The improvement in device performance is mainly due to the agreeable electrical properties and enhanced charge extraction of the CTAB-modified MoO3 ABLs, and CTAB modification to the MoO3 surface can effectively passivate its surface traps, suppress the recombination loss of carriers. The surface of CTAB-modified MoO3 films is also more hydrophobic than that of the PEDOT:PSS. In a word, these indicate the CTAB-modified MoO3 films may be used as a novel and generally applicable hole transport layer for high-efficiency and ambient stable polymer solar cells.

Low-Temperature Preparation of Tungsten Oxide Anode Buffer Layer via Ultrasonic Spray Pyrolysis Method for Large-Area Organic Solar Cells.

Tungsten oxide (WO3) is prepared by a low-temperature ultrasonic spray pyrolysis method in air atmosphere, and it is used as an anode buffer layer (ABL) for organic solar cells (OSCs). The properties of the WO3 transition metal oxide material as well as the mechanism of ultrasonic spray pyrolysis processes are investigated. The results show that the ultrasonic spray pyrolysized WO3 ABL exhibits low roughness, matched energy level, and high conductivity, which results in high charge transport efficiency and suppressive recombination in OSCs. As a result, compared to the OSCs based on vacuum thermal evaporated WO3, a higher power conversion efficiency of 3.63% is reached with low-temperature ultrasonic spray pyrolysized WO3 ABL. Furthermore, the mostly spray-coated OSCs with large area was fabricated, which has a power conversion efficiency of ~1%. This work significantly enhances our understanding of the preparation and application of low temperature-processed WO3, and highlights the potential of large area, all spray coated OSCs for sustainable commercial fabrication.

Effect of pentacene/Ag anode buffer and UV-ozone treatment on durability of small-molecule organic solar cells

Three surface modifications of indium tin oxide (ITO) are experimentally investigated to improve the performance of small-molecule organic solar cells (OSCs) with an ITO/anode buffer layer (ABL)/copper phthalocyanine (CuPc)/fullerene/bathocuproine/Ag structure. An ultrathin Ag ABL and ultraviolet (UV)-ozone treatment of ITO independently improve the durability of OSCs against illumination stress. The thin pentacene ABL provides good ohmic contact between the ITO and the CuPc layer, thereby producing a large short-circuit current. The combined use of the abovementioned three modifications collectively achieves both better initial performance and durability against illumination stress.