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As an alternative hole transport layer (HTL) to poly(3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), we investigated V 2 O 5 thin films fabricated by simple brush painting without any post-treatments. Polymer solar cells (PSCs) with V 2 O 5 fabricated by brush painting showed superior performance to that of conventional PEDOT:PSS based system; in particular, higher FF was obtained. Because more hydrophobic oxide surface induces better physical contact and better wetting of active blends, lower R S is obtained; thus, the resulting device shows higher performance. PSC with brush painted V 2 O 5 at 50 °C using 0.99 vol% vanadium (V) oxytriisopropoxide in isopropyl alcohol exhibited the best power conversion efficiency (PCE) of 3.83%. Furthermore, employment of V 2 O 5 as HTL leads to significant improvement in long-term stability in air (dropping of PCE of conventional PEDOT:PSS system to ~0% and retention of PCE of V 2 O 5 based PSC to over 60% after exposure in air for 96 h without any encapsulation). [ABSTRACT FROM AUTHOR]

Abstract: 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 1475S/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. [Copyright &y& Elsevier]

Abstract: As an alternative to the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transporting layer (HTL) in polymer solar cells (PSCs), moderately reduced graphene oxide (GO) films fabricated by simple and fast thermal treatment of solution processed GO were investigated. PSC with thermally treated GO at 250°C exhibited best performance with a power conversion efficiency (PCE) of 3.98%, compared to the PSC containing conventional PEDOT:PSS HTL with a PCE of 3.85%. Furthermore, the PSC with thermally treated GO showed superior stability compared to the PSC with conventional PEDOT:PSS HTL under the atmosphere condition without any encapsulation process. Our demonstration suggests that moderately reduced GO by simple thermal treatment could be promising HTL replacing PEDOT:PSS in PSCs as well as other organic electronics. [Copyright &y& Elsevier]

Abstract: We developed a novel hybridized electron-selective layer comprised of Sb-doped SnO2 nanowires for efficient inverted polymer solar cells. A device containing Sb-doped SnO2 nanowires with 0.1mg/ml concentration showed a significant increase in power conversion efficiency to 3.23% with an enhanced fill factor, compared to a reference device without the nanowires (2.89%). Such improvement is attributed to the high electrical conductivity of one-dimensional Sb-doped SnO2 nanowires and to the good light transmittance through the wide band gap of tin oxide. Also the surface morphology of the hybridized electron-selective layer is made denser and improved by incorporating one-dimensional Sb-doped SnO2 nanowires, resulting in the enhancement of the photovoltaic performance. [Copyright &y& Elsevier]

Abstract: Polyelectrolyte multilayer films composed of a polycation (poly(allylamine hydrochloride) PAH) and a polyanion (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS) were prepared by a spin self-assembly method, and their electrochemical and electrochromic properties were investigated. The change in the surface charge and the optical absorption spectra of the multilayer films revealed that sequential deposition of polyelectrolyte was successfully achieved during the spin self-assembly. The electrochromic properties of 20-bilayered PAH/PEDOT:PSS were also investigated. The response time for the coloring and bleaching processes was 6.2 and 2.5s, respectively, and the coloration efficiency was 199.3cm2/C. These results indicate that a spin self-assembly process could be a viable alternative for the fabrication of electrochromic devices. [Copyright &y& Elsevier]

CH 3 NH 3 PbI 3 -based planar perovskite solar cells were fabricated by slot-die coating, a scalable method. Slot-die coating tends to produce perovskite layers with much lower coverage with overgrown crystals than spin coating, which does not include a self-drying mechanism in the process. To mimic the self-drying behavior inherent in spin coating, the present study introduces a blowing step in the slot-die coating method, which significantly improved coverage of the prepared slot-die coated perovskite films. The slot-die-coated device with blowing showed a moderate power conversion efficiency (PCE) of 8.8%. The morphology of the slot-die-coated perovskite film is further improved by optimizing the deposition temperature. The combination of blowing and heating during the slot-die-coating step and the introduction of a printing-friendly hole transport layer resulted in a PCE of 12.7% for the devices fabricated in air. [ABSTRACT FROM AUTHOR]

An interfacial layer and active layer were simultaneously fabricated through a facile one-step process using a blended solution of zinc oxide (ZnO) sol-gel as the interfacial material, and P3HT:PCBM (poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric methyl ester) as the photoactive components. The resultant devices based on the one-step process exhibited a favourable 3.56% power conversion efficiency (PCE) after a simple UV light treatment, close to the PCE of a conventionally fabricated reference device with a multilayer architecture. Using a combination of surface morphology analysis and investigation of the vertical component distribution, we confirmed that a spontaneous and significant phase separation between the ZnO and the photoactive materials occurred during the spin coating and sequential thermal annealing processes. This resulted in the automatic formation of an enriched ZnO interfacial layer at the ITO surface. The work function of the ZnO layer deposited by the one-step process on the ITO substrate was 3.76 eV, consistent with conventionally formed ZnO layers. Furthermore, the performance of the device fabricated by the one-step process demonstrated superior stability under light exposure. This successful demonstration of organic photovoltaics (OPVs) using the one-step process is an important step towards the realization of high performance, roll-to-roll compatible OPVs. [ABSTRACT FROM AUTHOR]

Abstract: Polymer solar cells (PSCs) based on alkyl-substituted thienylenevinylene and phthalimide-based D-A copolymer (PTVPhI-Eh) as a donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an acceptor were investigated with the intent of gaining high performance photovoltaic properties. PTVPhI-Eh had a deep highest-occupied molecular orbital (HOMO) level, ~0.3eV lower than rr-P3HT. As a result, PTVPhI-Eh:PC71BM devices showed a high open circuit voltage (V oc ) of 0.87V, which is over 0.2V higher compared to that of P3HT:PCBM-based PSCs. The maximum power conversion efficiency (PCE) of PSCs was 4.14% with V oc of 0.87V, short circuit current (J sc ) of 7.32mA/cm2, and fill factor (FF) of 65%, under optimized conditions of a 1:1wt/wt ratio and treatment with a 2vol% 1-chloronaphthalene solvent additive. The V oc and consequent photovoltaic performance of this PSC was significantly affected by the concentration of the solvent additive. To determine the relationship between V oc and concentration of solvent additive, PTVPhI-Eh:PC71BM devices were investigated with various analyses such as optical spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). [Copyright &y& Elsevier]

Abstract: The work-function of indium tin oxide (ITO) electrodes was tuned with an interfacial dipole layer (WPF-oxy-F) to reverse the polarity in polymer solar cells (PSCs) with an inverted structure. The photoactive layer was based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Silver (Ag) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were used as the top anode. The optimized conditions for the fabricated I-PSCs included an open-circuit voltage (V oc) of 0.68V, a fill factor (FF) of 64%, and a power conversion efficiency (PCE) of 3.86% through post-annealing at 170°C. The high performance of I-PSC is due partly to the improved interfacial contact at active/PEDOT:PSS and mainly to the increase of the work-function of annealed PEDOT:PSS/Ag at 170°C for 30min. Here, we investigated the effect of post-annealing on I-PSC devices by carrying out various annealing sequences. [Copyright &y& Elsevier]

Abstract: We report on cost-effective and ITO-free polymer solar cells (PSCs) fabricated on the copper (Cu) sheets consisting mainly of a Cu electrode and a polyimide substrate. The Cu electrode was used as a bottom cathode in inverted PSCs, and each layer above the Cu sheet was all-solution-processed. The work-functions of Cu electrodes were engineered with an interfacial dipole layer to enhance the device-performance. Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (hcPEDOT:PSS) was used as a transparent top anode, and a photoactive layer was based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The fabricated PSCs exhibited a power conversion efficiency (PCE) of ∼2.5%, demonstrating PSCs fabricated on Cu sheets have the great potential for cost-effective power generators. This study could be an important approach to the development of all-solution-processed and roll-to-roll PSCs using low-cost Cu electrodes as a cathode. [Copyright &y& Elsevier]

Abstract: 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 63.3Ω/squares, respectively, corresponding to an increase in film thickness. The best device exhibited a high power conversion efficiency of 2.17% under 100mWcm−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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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 (<50°C), we can obtain the flexible ITO electrode with a sheet resistance of 47.4Ω/square and an average optical transmittance of 83.46% in the green region of 500–550nm 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 roll-to-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 sputtering process in preparing flexible transparent electrodes for flexible solar cells or displays. [Copyright &y& Elsevier]

A nanostructured micro-prism array (MPA) was integrated onto a solar module consisting of multiple perovskite solar cells (PeSCs) to minimize optical losses from surface reflection and the inactive areas reserved for interconnection. The MPA structure redirects light that is incident on inactive areas onto active sub-cell areas to improve the light harvesting efficiency. The nanoscale sub-wavelength structures (SWSs) minimize the surface reflection at the surface of the PeSC module. Combining the technical advantages of these two structures, the MPA decorated with nanoscale SWSs improves the performance of the PeSC module. The short circuit current of the PeSC module employing the MPA decorated with nanoscale SWSs was improved by 1.4 mA/cm2 compared to a conventional PeSC module covered with bare glass. • A 1 × 4 monolithic perovskite solar cell module was fabricated. • To enhance the light harvesting, the nanostructured MPA was applied onto the module. • The optical characteristics of the nanostructured MPA were analyzed. • The J sc of the module integrated with nanostructured MPA are relatively improved by 36.8%. [ABSTRACT FROM AUTHOR]