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Perovskite photovoltaics (PePVs) tend to suffer from a high density of defects that restricts the device in terms of -performances and -stability. Therefore, defect passivation and film-quality imp...

To find promising device architecture for air-stable as well as efficient semitransparent perovskite solar cells (PeSCs), Ag & Cu semitransparent top electrode and interfacial engineering technologies are explored in PeSCs consisting with indium tin oxide (ITO)/hole transporting layer (HTL)/CH3NH3PbI3/[6,6]-phenyl-C61 butyric acid methyl ester (PCBM)/Ag or Cu. Devices with NiOx HTL exhibits better performance than conventional poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) based devices and modification of PCBM with polyethylenimine ethoxylated (PEIE) also induces improved performance. Optimized semitransparent PeSC with Cu shows superior performance, achieving a power conversion efficiency (PCE) of 11.95% and average visible transmittance (AVT) of ∼20%, and stability to Ag based device.

In parallel with soaring efficiency, interest in multi-functional semitransparent perovskite solar cells (PeSCs) has emerged for special applications such as windows and tandem cells. To demonstrate air-stable as well as efficient ITO-free semitransparent PeSCs, ultra thin Cu and Ni, which are well-known non-precious metals having sufficient electrical conductivity, are investigated as bottom transparent electrode and optimization of devices is systematically carried out. Semitransparent Ni/NiOX based PeSC exhibits the average visible transmittance (AVT) of 22% and power conversion efficiency (PCE) of 8.20%. Considering required AVT for the application of power-generating window of ∼25% and recent reports, this result is one of the best performances reported to date.

We demonstrate a simple solution and room-temperature processed reduced graphene oxide (RGO) as a novel hole-transporting material (HTM) to guarantee highly efficient and highly stable CH3NH3PbI3 perovskite solar cells (PeSCs). The effects of RGO HTM are systemically investigated in terms of PeSC efficiency, PeSC stability, morphology of perovskite film, recombination dynamics, and charge-transport through CH3NH3PbI3/HTM interface. The resultant PeSC with a planar configuration of glass/ITO/RGO/CH3NH3PbI3/PC61BM/bathocuproine (BCP)/Ag exhibits improved device efficiency (maximum PCE of 10.8%) with high reproducibility than those of the reference devices using conventional PEDOT:PSS and GO HTMs. Also, the RGO-based PeSCs show highly desirable device stability in comparison to the PEDOT:PSS PeSCs.

Morphological, optical, and electrical properties of solution-processed reduced graphene oxide (r-GO) thin-films are investigated by varying on the number of spin-coating cycles and annealing temperature. Spin-coated r-GO thin-films all show full-covered morphologies with highly small rms roughness values ranging from ∼1 to 2.5 nm. The sheet resistance of r-GO films can be controlled over two orders of magnitude by controlling both the spin-coating cycles and annealing temperature while conserving the transmittance values of 57–87%. The combination of coating cycles and heat-treatment temperature make the r-GO films as a useful transparent hole-extraction electrode for the application to organic photovoltaic cells.

In this work, we have demonstrated that simple brush-painted Ti-doped In2O3(TIO) films can be used as a cost effective transparent anodes for organic solar cells (OSCs). By the direct brushing of TIO nanoparticles ink and rapid thermal annealing (RTA), we can simply obtain TIO electrodes with a low sheet resistance of 28.25 Ω/□ and a high optical transmittance of 85.48% under atmospheric ambient conditions. In particular, the brush painted TIO films showed a much higher mobility (33.4 cm2/V s) than that of previously reported solution-process transparent oxide films (1–5 cm2/V s) due to the effects of the Ti dopant with higher Lewis acid strength (3.06) and the reduced contact resistance of TIO nanoparticles. The OSCs fabricated on the brush-painted TIO films exhibited cell-performance with an open circuit voltage (Voc) of 0.61 V, shot circuit current (Jsc) of 7.90 mA/cm2, fill factor (FF) of 61%, and power conversion efficiency (PCE) of 2.94%. This indicates that brush-painted TIO film is a promising cost-effective transparent electrode for printing-based OSCs with its simple process and high performance.

We report highly transparent Ag-doped In2O3 (IAO) films with high work function for use as transparent anodes in organic solar cells (OSCs). The electrical, optical, structural, and morphological properties of IAO films and their work function were investigated as a function of the rapid thermal annealing (RTA) temperature. At an RTA temperature of 600 °C, the IAO film showed a sheet resistance of 23.12 Ohm/square, an optical transmittance of 79.28%, and a work function of 5.21 eV, similar to conventional Sn-doped In2O3 (ITO) films. The low resistivity of the IAO film was closely related to oxygen vacancies caused by Ag suboxide formation in the In2O3 matrix. A bulk-heterojunction OSC with the optimized IAO anode showed performance comparable to that of an OSC with a reference ITO anode, indicating that the IAO films is a promising anode material for use in OSCs.

We demonstrate cost-effective, indium tin oxide (ITO)-free organic solar cells (OSCs) fabricated with a silver nanowire (AgNW)–poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite electrode. The composite films were prepared with a one-step spray-coating of a mixture composed of AgNW and a highly conductive, dimethylsulfoxide (DMSO)-treated PEDOT:PSS (hcPEDOT). The film-thickness, optical transmittance, and sheet resistance of AgNW–hcPEDOT hybrid electrodes were easily controlled by varying the spray deposition time. With AgNW–hcPEDOT composite electrodes, the devices exhibited high power conversion efficiencies of up to 2.16% under 100 mW cm−2 and AM 1.5G illumination conditions. In addition, the surface of the AgNW–hcPEDOT composite electrodes was further smoothened with an additional spray-coated PEDOT:PSS buffer layer, leading to reduced shorting and improved cell-efficiency. As a result, the best performing devices with a AgNW–hcPEDOT electrode and spray-coated PEDOT buffer exhibited efficiencies of up to 2.65%, which approaches that of conventional ITO-based devices. These results indicate that the one-step spray-coated AgNW–hcPEDOT composite-based film is a viable alternative to the high-cost and vacuum-deposited ITO for mass-production and low-cost roll-to-roll based solar cells.

We propose that an indium zinc tin oxide electrode grown by linear facing target sputtering without additional thermal treatment can effectively act as an efficient semi-transparent top electrode for high-performance semi-transparent hybrid perovskite solar cells. The semi-transparent perovskite solar cells using an indium zinc tin oxide electrode as a novel top electrode achieves a power conversion efficiency of 12.85%, similar to that of an opaque electrode-based device of 13.48%. More importantly, by adjusting the perovskite thickness, a power conversion efficiency of 8.306% is obtained at an average visible transmittance of 33.9%, thus well supporting that the indium zinc tin oxide electrode can be considered to be an advanced and efficient semi-transparent top electrode for the fabrication of building integrated photovoltaics with high efficiency and good transparency.

We demonstrate that pitch-converted carbon nanosheet (CNS) films can efficiently function as transparent conducting electrodes for polymer solar cells (PSCs). The solution-processed CNS film was prepared with spin-coating of a cost-effective pitch solution dissolved in dimethylformamide on quartz substrates, followed by stabilization and carbonization treatments to convert the pitch into CNS. The pitch-converted CNS films prepared by the successive heat-treatment process were examined as a novel transparent anode in solar cells, and as a result, PSCs fabricated directly on such CNS electrodes exhibited a high power conversion efficiency of ∼1.7% under 100 mWcm −2 illumination and AM 1.5 G conditions. This approach could be highly desirable for advancing the realization of fully printable and flexible low-cost transparent electrodes for indium tin oxide (ITO)-free polymer solar cells.

We report an effective 2-step solvent treatment combined with a polar solvent vapor annealing process (PSVA) and a dipping process using polar solvents (DP) to enhance the electrical conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films, which is highly desirable for the fabrication of solution-processed organic photovoltaics (OPVs) on flexible substrates. The PSVA and DP-treated PEDOT:PSS films showed conductivities up to 1475 S/cm. The changes in conductivity, surface morphology, composition, and conformational PEDOT chains are investigated to elucidate the effect of the 2-step PSVA and DP treatment on PEDOT:PSS films. The highly segregated-PSS component induced by PSVA was effectively removed from the PEDOT:PSS films after successive DP treatments, eventually resulting in an enhanced conductivity of bulk films. We also employed optimized PEDOT:PSS films treated by the 2-step PSVA and DP-process as transparent anodes for indium tin oxide (ITO)-free OPVs fabricated on flexible substrates. The device performance of flexible OPVs with PSVA and DP-treated films was further improved due to the increased conductivity and decreased series resistance of devices and showed highly comparable cell-efficiency with ITO-based flexible OPVs. These results suggest that the 2-step solvent-treated PEDOT:PSS film is a promising alternative to ITO for realization of high-efficiency, flexible, and low-cost ITO-free OPVs with facile manufacturing process.

We report on cost-effective ITO-free organic solar cells (OSCs) fabricated by a spray deposition method. All solution-processable layers of solar cells—a highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer and a photoactive layer based on poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM)—were spray-coated. PEDOT:PSS anode films with various thicknesses were prepared by controlling the spray deposition time. The transmittance and sheet resistance of PEDOT:PSS anodes were varied from 89.0% to 67.4% and from 358 to 63.3 O/squares, respectively, corresponding to an increase in film thickness. The best device exhibited a high power conversion efficiency of 2.17% under 100 mW cm 2 illumination with air mass (AM) 1. 5 global (G) condition. More importantly, the efficiency of the fully spray-coated OSC with the PEDOT:PSS anode was comparable to that of conventional ITO-based devices, demonstrating the feasibility of fabricating all-spray-deposited OSCs without a conventional spin-coating method and the possibility of replacing the costly vacuum-deposited indium tin oxide (ITO) with highly conductive polymer films fabricated by inexpensive spray deposition techniques.

We report on the fabrication of efficient annealing-free polymer solar cells via simple brush painting considered as a promising method for the mass production of organic devices based on the high-speed roll-to-roll system. Higher device efficiency could be obtained compared to the spin-coated devices, resulting from the improved organization of polymer chains and better balanced carrier transport induced by more effective application of shear stress to the polymer chains during the brushing process. In addition, fully brush painted solar cells, including the brush-painted PEDOT:PSS and photoactive layer, presented a high power conversion efficiency of 3.6% without any annealing treatment and processing additives.

Here, an investigation of three-dimensional (3D) morphologies for bulk heterojunction (BHJ) films based on regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is reported. Based on the results, it is demonstrated that optimized post-treatment, such as solvent annealing, forces the PCBM molecules to migrate or diffuse toward the top surface of the BHJ composite films, which induces a new vertical component distribution favorable for enhancing the internal quantum efficiency (ηIQE) of the devices. To investigate the 3D BHJ morphology, novel time-of-flight secondary-ion mass spectroscopy studies are employed along with conventional methods, such as UV-vis absorption, X-ray diffraction, and high-resolution transmission electron microscopy studies. The ηIQE of the devices are also compared after solvent annealing for different times, which clearly shows the effect of the vertical component distribution on the performance of BHJ polymer solar cells. In addition, the fabrication of high-performance P3HT:PCBM solar cells using the optimized solvent-annealing method is reported, and these cells show a mean power-conversion efficiency of 4.12% under AM 1.5G illumination conditions at an intensity of 100 mW cm−2.

The preparation and characteristics of flexible indium tin oxide (ITO) electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible organic solar cells are described. It was found that both electrical and optical properties of the flexible ITO electrode were critically dependent on the Ar/O2 flow ratio in the continuous roll-to-roll sputter process. In spite of the low substrate temperature (o501C), we can obtain the flexible ITO electrode with a sheet resistance of 47.4O/square and an average optical transmittance of 83.46% in the green region of 500–550 nm wavelength. Both X-ray diffraction and field emission scanning electron microscopy analysis results showed that all flexible ITO electrodes grown on the PET substrate were amorphous with a very smooth and featureless surface, regardless of the Ar/O2 flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion-beam-treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet-cleaned PET substrates, due to an increased adhesion between the flexible ITO and the PET substrates. Furthermore, the flexible organic solar cell fabricated on the rollto-roll sputter-grown flexible ITO electrode at an optimized condition exhibited a power conversion efficiency of 1.88%. This indicates that the roll-to-roll sputtering technique is a promising continuous

Polymer-based photovoltaic cells, with periodic sub-micrometer structures as an efficient light-trapping scheme, are investigated to improve the performance of organic solar cells based on poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61. A soft lithographic approach that uses photoresponsive azo polymer films as masters and poly(dimethylsiloxane) as stamps is used to form surface relief gratings (SRGs) on the active layers. The effect of periodic gratings on solar cell performance is precisely investigated according to various grating conditions such as period, depth, and dimension. The solar cells with 1D and 2D SRGs present improved incident-photon-to-current conversion efficiencies and an overall increase in power conversion efficiencies, primarily resulting from the enhancement of short-circuit current density, indicating that periodic structures induce further photon absorption in the active film.

Despite the relatively low efficiencyin comparison with conventional inorganic solar cells, thepotential of roll-to-roll processing and large-area processa-bility on flexible low-cost substrates renders conjugatedpolymer-based organic solar cells (OSCs) very attractive asa cost-effective solution to the problem of energy shortage.Among the available BHJ systems, poly(3-hexylthiophene)(P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C

Data are presented on high performance and air-stable organic solar cells with modified electrode architecture (MAOSCs), which have a patterned transparent anode determining the real active area of devices and a large area of reflective cathode covering the whole area of an active layer based on poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM). Based on the finite-difference time-domain (FDTD) scheme as a numerical method, improved light trapping within the photoactive layer, resulting from the efficient reflection of incident light at the large area of cathode, can be attained by modifying the conventional organic solar cell structures. Here, an improved power conversion efficiency of 4.3% was obtained in the case of MAOSCs under 1 Sun with air mass (AM) 1.5 global (G) condition. In addition, the stability of MAOSCs in air was remarkably improved due to the limited exposure of their active layers to air.

The electronic properties of quantum dots can be tuned by changing the size of particles without any change in their chemical composition. CdSe quantum dots, the sizes of which were controlled by changing the concentrations of Cd and Se precursors, were adsorbed on photoelectrodes and used as sensitizers for photovoltaic cells. For applications of CdSe quantum dot as sensitizers, films on conducting glass were employed in a sandwich-type cell that incorporated a platinum-coated conductive glass and an electrolyte consisting of an redox. The fill factor (FF) and efficiency for energy conversion () of the photovoltaic cell was 62 % and 0.32 %, respectively.

New type counter electrodes comprised of Pt and a metal oxide biphase, Pt–NiO and Pt–TiO 2 , were prepared by RF magnetron co-sputtering system for use in dye-sensitized solar cells. Transmission electron microscope images confirmed the formation of ∼3 nm nanosized Pt polycrystalline mixed with metal oxide phase, which has higher active surface area than a conventional Pt electrode. When the Pt–TiO 2 counter electrode was used in the cell, the power conversion efficiency was increased up to ∼1.56 times, compared to conventional devices composed of a Pt electrode under 1 Sun with air mass 1.5 Global illumination due to its superior electrocatalytic activity and efficient reflection of incident light at the counter electrode.

For use in hybrid solar cells consisting of TiO2 and poly[2-methoxy, 5-(2 � -ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV), a TiO2 nanostructure which has periodic hexagonal hole arrays was fabricated using surface relief gratings on azobenzene-functionalized polymer films as a template in the sol–gel reaction of a Ti-precusor. The ordered bulk heterojunction solar cells, prepared with the TiO2 nanostructure and MEH-PPV, have a higher power conversion efficiency of 0.21% compared to bilayer and random bulk heterojunction solar cells fabricated with thin-dense TiO2 films and randomly networked TiO2 nanoparticles, respectively, under one sun with air mass 1.5 global illumination. © 2007 Elsevier B.V. All rights reserved.

Pt electrodes were prepared by direct and pulse current electrodeposition for use as counter electrodes in dye-sensitized solar cells. Scanning electron microscope and transmission electron microscope images confirmed the formation of uniform Pt nanoclusters of ∼40 nm composed of 3 nm nanoparticles, when the pulse current electrodeposition method was used, as opposed to the dendritic growth of Pt by the results from direct current electrodeposition. By applying pulse electrodeposited Pt which has a 1.86 times higher surface area compared to direct current electrodeposited Pt, short-circuit current and conversion efficiency were increased from 10.34 to 14.11 mA/cm2 and from 3.68 to 5.03%, respectively. In addition, a flexible solar cell with a pulse current electrodeposited Pt counter electrode with a conversion efficiency of 0.86% was demonstrated.

A photoelectrode using ZnO coated TiO2 nanoparticles was prepared for use in flexible dye-sensitized solar cells. To provide an inherent energy barrier between the electrode and electrolyte interface, the surface of the TiO2 nanoparticles was modified by thin ZnO layer. X-ray photoelectron spectroscopy and transmission electron microscopy image confirmed the formation of ZnO with a thickness of ca. ∼0.5 nm, possible thickness for tunneling process in particle-to-particle transport of electrons, on the TiO2 surface. The overall conversion efficiency was increased from 0.71 to 1.21% under a light intensity of 20 mW/cm2 (0.2 sun) due to the reduced recombination of photoinjected electrons without any post-treatment.

The maskless selective wet etching of p-GaN layer with KOH in ethylene glycol (KE) and H3PO4/H2SO4 (HH) acids was developed for the highly efficient light-emitting diodes (LEDs). The p-GaN surfaces textured by the selective wet etching process without using etch mask showed hexagonal and stripe shapes in the KE and HH solutions, respectively. The current-voltage (I-V) characteristics of the LED textured by KE and HH solutions showed improved electrical properties compared to the non-etched LED. This result could be attributed to a reduced contact resistance due to an increased contact area between the metal electrode and p-GaN layer. In addition, the light-output power of the LED textured by KE and HH solutions was improved by 29.4% and 36.8% relative to that of the non-etched LED. This result was attributed to the increase in probability of escaping photons from the LED and the reduction of surface defects by the maskless selective wet etching process. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Y3Al5O12:Ce0.05 phosphor particles were coated on flexible indium tin oxide-coated polyethylene terephthalate by electrophoretic deposition to achieve a uniform and high packed coating. White light was obtained using the flexible YAG phosphor layer and a blue unpackaged GaN chip without direct coating onto a GaN chip. The chromaticity of the white light was x = 0.2994, y = 0.3272, which corresponded to good quality white light. As part of a study of the electrophoretic deposition of Y3Al5O12:Ce0.05 yellow phosphor, zeta potential was measured in isopropyl alcohol at various concentrations of electrolyte. The zeta potential of the phosphor was dependent on the concentration of salt such as Mg(NO3)2 in suspension.

1 School of Materials Science and Engineering, Heeger Center for Advanced Materials (HCAM), Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea 2 Korea Institute of Science and Technology (KIST), Institute of Advanced Composite Materials, Jeollabuk-do 565-902, Korea 3 Department of Nano & Chemical Engineering, Kunsan National University, 753-701, Kunsan, Jeollabuk-do, 753-701, Korea 4 School of Nanobio Materials and Electronics, Research Institute for Solar and Sustainable Energies (RISE), GIST, Gwangju 500-712, Korea

The interfacial properties of PEDOT:PSS, pristine r-GO, and r-GO with sulfonic acid (SR-GO) in organic photovoltaic are investigated to elucidate electron-blocking property of PEDOT:PSS anode interfacial layer (AIL), and to explore the possibility of r-GO as electron-blocking layers. The SR-GO results in an optimized power conversion efficiency of 7.54% for PTB7-th:PC71BM and 5.64% for P3HT:IC61BA systems. By combining analyses of capacitance–voltage and photovoltaic-parameters dependence on light intensity, it is found that recombination process at SR-GO/active film is minimized. In contrast, the devices using r-GO without sulfonic acid show trap-assisted recombination. The enhanced electron-blocking properties in PEDOT:PSS and SR-GO AILs can be attributed to surface dipoles at AIL/acceptor. Thus, for electron-blocking, the AIL/acceptor interface should be importantly considered in OPVs. Also, by simply introducing sulfonic acid unit on r-GO, excellent contact selectivity can be realized in OPVs.

The selective wet etching of a p-GaN layer by using a solution of KOH in ethylene glycol (KE) was studied to enhance the optical and electrical performance of the GaN-based light-emitting diodes (LEDs). The surface of the p-GaN, which was selectively etched in the KE solution, showed hexagonal-shaped etch pits. The light-output power of etched LEDs was improved by 29.4% compared to that of the nonetched LED. This improvement was attributed to the increase in the probability of photons to escape due to the increased surface area of textured surface and the reduction in contact resistance of the ohmic layer resulting from the increased contact area and hole concentration on the textured p-GaN. The reverse leakage current of the LED was also greatly decreased due to the surface passivation and the removal of defective regions from the p-GaN.

The potential of a fl exible, roll-to-roll manufacturing process has made bulk-heterojunction (BHJ) organic solar cells (OSCs) very attractive as a promising solution to energy and environmental issues. [ 1–8 ] In polymer solar cells, device characteristics such as fi ll factor (FF), short-circuit current density (J sc ) and open-circuit voltage (V oc ) as well as the cell life-time all are highly dependent on the interface properties between the electrodes and the active layers and on the bulk properties of the materials. [ 9 ] For these reasons, numerous modifi cations of electrodes by introduction of an interfacial layer have been studied intensively for high-performance and stable OSCs, [ 10–15 ] and several key factors such as transparency, conductivity, passivation property, fi lm morphology, stability, and solution-processability have been considered for uses of these promising interfacial layers. [ 9–15 ]

We introduce a simple but effective graphene oxide (GO) modification with metal chloride treatments to produce high-performance polymer solar cells (PSCs). The role of various metal chlorides on GO and their effects on device performances of PSCs was investigated. X-ray photoelectron spectroscopy, ultraviolet photoemission spectroscopy, and current-voltage measurement studies demonstrated that metal chloride can induce a p-doping effect and increase the GO work-function, thus resulting in an improved built-in potential and interfacial resistance in PSCs. The resultant PSCs with metal chloride exhibited improved device efficiency than those with the neat GO. Furthermore, with the metal chloride-doped GO, we finally achieved an excellent PSC-efficiency of 6.58% and a very desirable device stability, which constitute a highly similar efficiency but much better PSC life-time to conventional device with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). This study could be a valuable way to produce various PEDOT:PSS alternatives and beneficial for producing high-performance and cost-efficient polymeric devices.

We demonstrate highly efficient organic-based Schottky junction solar cells (OSJSCs) obtained by poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) modification with solution-processed platinum chloride (PtCl4) treatment. The effect of PtCl4 on PEDOT:PSS properties and device performances of solar cells was investigated. Kelvin probe and 4-point probe studies demonstrated that PtCl4 decreased the PEDOT:PSS sheet-resistance and increased the PEDOT:PSS work-function, thereby inducing an improved built-in potential and interface resistance. As a result, with the aid of the PtCl4 treatment, the Schottky junction device had a high power conversion efficiency of 3%, which was more than 20% higher than the reference OSJSCs with no PtCl4, indicating that PtCl4 can be a promising PEDOT:PSS modifier for raising the cell-performances of Schottky-junction based organic solar cells.

This study examined the effects of a sheet resistance of silver nanowire (AgNW)-based electrode on the cell-performances in indium tin oxide (ITO)-free organic solar cells (OSCs) fabricated with AgNWs and highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) bilayer electrodes (AgNWs/hcPEDOT). The transmittance and sheet resistance (Rsh) of AgNWs/hcPEDOT electrodes were controlled by varying the spin-coating cycle of AgNW films. Variations in cell-performances including the power conversion efficiency (PCE), the short-circuit current density (Jsc), and the fill factor (FF) that resulted from varying the Rsh of AgNW-based films were systematically studied. With reducing Rsh of transparent electrodes, the FF and the series resistance were continuously improved, but the OSC with the highest FF showed a low Jsc value due to the decrease in transmittance with increasing AgNW density. As a result, an optimum OSC showed a PCE of 2.699%, which is a slightly low PCE value compared with ITO-based OSCs. These results indicate that the cell-performance of OSCs is highly dependent on Rsh of the AgNW-based electrode and that a trade-off between Rsh and transmittance of transparent electrodes should also be considered to perfectly replace the conventional ITO and to achieve higher device-efficiency.

We have demonstrated cost-effective ITO-free polymer solar cells (PSCs) with ink-jet-printed current collecting Ag grids in combination with highly conductive PEDOT:PSS as a composite transparent electrode. By ink-jetting of Ag nano-particle solution, we were able to obtain ink-jet-printed Ag grids with sheet resistance of 15.8 Ω/square and optical transmittance of 82.51% at 550 nm wavelength. Furthermore, the ITO-free PSC with the composite transparent anode on flexible substrates exhibited excellent cell-performances: fill factor of 64.72%, short-circuit current density (Jsc) of 6.301 mA cm−2, open-circuit voltage (Voc) of 0.562 V and power conversion efficiency of 2.292%, indicating the ink-jet-printed grid-based electrode is a visible alternative to cost-intensive sputter-grown ITO electrodes and a promising printing-based electrode for realization of fully printed and flexible ITO-free photovoltaic devices.

Enhanced performance of inverted polymer solar cells (PSCs) is demonstrated by indium tin oxide (ITO) interfacial tuning via a water-soluble polyfluorene (WPF-6-oxy-F). Kelvin probe studies and dark current-voltage curves demonstrated that the WPF-6-oxy-F layer reduces the ITO work-function because of the favorable interfacial dipole formed by the WPF-6-oxy-F interlayer, thereby enhancing the built-in potential and reducing the interface resistance. As a result, introduction of the WPF-6-oxy-F by simple solution processing into the inverted PSCs dramatically enhanced cell-performances. This approach could be very beneficial and an important step for the future development of all-solution-processed or roll-to-roll processed PSCs.

To enhance solar harvesting in organic solar cells, uniform-sized metal nanoparticles of ∼13 nm were incorporated to the device via pulse-current electrodeposition, which is a kind of simple and quick solution process that can control the density and size of metal nanoparticles. By incorporating plasmonic Ag nanoparticles on surface modified transparent electrodes, overall power conversion efficiency was increased from 3.05% to 3.69%, mainly resulting from the improved photocurrent density as a result of enhanced absorption of the photoactive conjugate polymer due to the high electromagnetic field strength in the vicinity of the excited surface plasmons.

The use of periodic submicrometer structures as an efficient light-trapping scheme was investigated for high performance organic solar cells (OSCs) based on poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61. The gratings on an active layer are achieved by a soft lithographic approach using photoinduced surface-relief gratings (SRGs) on azo polymer films and poly(dimethylsiloxane) as a master and stamp, respectively. Incident photon to current conversion efficiency and the power conversion efficiency of OSC with gratings increased primarily due to enhanced short circuit current density, indicating that SRGs induce further photon absorption in active layers by increasing the optical path length and light trapping.

The authors report on a spray deposition method as a cost-efficient technique for the fabrication of organic solar cells (OSCs). Active layers of OSCs were fabricated using conventional handheld airbrushes. Although the spray deposited film showed a relatively rougher surface than spin coated ones, pinhole-free and constant thickness films could be obtained. An optimized OSC showed 2.83% of power conversion efficiency and 52% of incident photon to current conversion efficiency even though the device was fabricated in air. The performance of sprayed OSCs was comparable to that of the spin coated devices fabricated in air.

Au/poly2–methoxy-5–2–ethylhexyloxy-1,4–phenylenevinyleneMEH-PPV composite films were prepared by electrodeposition of Au nanoparticles using two deposition conditions followed by the spin coating of MEH–PPV. In spite of the similar average particle size, surface plasmon bands and the bandwidth of the two types of Au nanoparticles were different from each other due to the particle density. The electrochromic coloration of Au/MEH–PPV films was modified when compared to pure MEH–PPV films, in that a new coloration band originating from the surface plasmon band of Au nanoparticles appeared. Depending on the types of Au nanoparticles, the electrochromic coloration of the composite films was also strongly influenced.

TiN nanocrystals formed by a co-sputtering method have been investigated as discrete charge traps for metal–oxide–nitride–oxide–silicon-type nonvolatile memory devices. The formation of isolated TiN nanocrystals embedded in Al2O3 was confirmed by transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction analyses. In addition, superior thermal stability of TiN nanocystals embedded in Al2O3 was confirmed. Compared to the control samples without TiN nanocrystals, Al2O3 layers with TiN nanocrystals exhibited wider capacitance–voltage hysteresis and this in turn showed better charge trapping characteristics due to the incorporation of TiN nanocrystals into Al2O3.