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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 studied the effects of perovskite precursor solvents and deposition temperatures on perovskite-layer formation for slot-die coating based solar cell fabrication. To select better solvent and temperature conditions, various representative polar solvents (dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone, N,N-dimethylformamide (DMF), γ-butyrolactone) and various deposition temperatures (70 °C–150 °C), well-known as key conditions in conventional spin-coating systems, were studied and compared. Comparative studies revealed the DMSO:DMF (5:5) solvents and the 130 °C can provide better solar-cell performances with cell-efficiency up to 15.40% in slot-die based planar perovskite devices, demonstrating an advanced step for better-efficiency slot-die-coating based perovskite solar cells.

We introduce that a solution-processed small molecule ITIC can effectively function as the ETL for the fabrication of high-performance organic–inorganic hybrid perovskite solar cells (PeSCs). The role and effect of ITIC on device performances was studied using field emission scanning electron microscope, surface potential image, atomic force microscopy, and internal resistances in PeSCs. As a result, we finally achieved a high PCE of 11.94% in the PeSC with an optimum ITIC comparable with the PCBM-based device. This approach suggests that non-fullerene small molecules ITIC could be considered as a promising interfacial material for achieving highly efficient PeSCs.

Phenyl-C61-butyric acid methyl ester (PCBM) is universally used as the electron-transport layer (ETL) in the low-cost inverted planar structure of perovskite solar cells (PeSCs). PCBM brings tremendous challenges in upscaling of PeSCs using industry-relevant methods due to its aggregation behavior, which undermines the power conversion efficiency and stability. Herein, we highlight these, seldom reported, challenges with PCBM. Furthermore, we investigate the potential of nonfullerene indacenodithiophene (IDT)-based molecules by employing a commercially available variant, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3- d:2',3'- d']- s-indaceno[1,2- b:5,6- b'] dithiophene (ITIC), as a PCBM replacement in ambient-processed PeSCs. Films fabrication by laboratory-based spin-coating and industry-relevant slot-die coating methods are compared. Although similar power-conversion efficiencies are achieved with both types of ETL in a simple device structure fabricated by spin-coating, the nanofibriller morphology of ITIC compared to the aggregated morphology of PCBM films enables improved mechanical integrity and stability of ITIC devices. Upon slot-die coating, the aggregation of PCBM is exacerbated, leading to significantly lower power-conversion efficiency of devices than spin-coated PCBM as well as slot-die-coated ITIC devices. Our results clearly indicate that IDT-based molecules have great potential as an ETL in PeSCs, offering superior properties and upscaling compatibility than PCBM. Thus, we present a short summary of recently emerged nonfullerene IDT-based molecules from the field of organic solar cells and discuss their scope in PeSCs as electron or hole-transport layer.

To demonstrate efficient and reliable indium thin oxide (ITO)-free organic solar cells (OSCs), we fabricated highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrodes by two-step brush-painting of PEDOT:PSS and dimethyl sulfoxide (DMSO). While one-step brush-painted electrodes with PEDOT:PSS and DMSO mixed solution showed large deviation in morphology and efficiency, uniform and highly conductive PEDOT:PSS electrodes were obtained by successive brush-painting of PEDOT:PSS and DMSO, respectively. ITO-free OSC exhibiting power conversion efficiency (PCE) of 3.74% was successfully demonstrated by optimized successive brush-painting.

Air-stable inverted polymer solar cells (IPSCs) were demonstrated by incorporating ZnO electron transport layer (ETL) fabricated with low-cost and simple brush-painting. IPSC with brush-painted ZnO using commonly used 0.75 M zinc acetate solution in 95% 2-methoxyethanol and 5% ethanolamine showed poor efficiency and reproducibility. By optimizing precursor solution and substrate temperature, thieno[3,4-b]thiophene/benzodithiophene (PTB7): [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) based IPSC with high power conversion efficiency (PCE) of 7.63% and desirable device stability was achieved. This indicates that because optimized process conditions are not necessarily transferrable between different techniques, it is worthy of investigation and discussion.

In this data article, we introduced the hysteresis of planar perovskite solar cells (PSCs) fabricated using dimethylformamide (DMF), gamma-butyrolactone (GBL), methyl-2-pyrrolidinone (NMP), dimethylsulfoxide (DMSO), DMF-DMSO, GBL-DMSO and NMP-DMSO as perovskite precursor solutions according to different scan directions, sweep times, and current stability. The hysteresis analyses of the planar PSCs prepared with a glass-ITO /NiOX/perovskite /PC61BM/BCP/Ag configuration were measured with Keithley 2400 source meter unit under 100 mW/cm2 (AM 1.5 G). The data collected in this article compares the hysteresis of PSCs with different solvents and is directly related to our research article “High-Performance Planar Perovskite Solar Cells: Influence of Solvent upon Performance” (You-Hyun Seo et al., 2017 [1] ).

We systemically studied the influence of various precursor solvents on perovskite films and their effects on solar cell performances in p-i-n planar-structured perovskite solar cells (PSCs). For comprehensive and reasonable consideration to achieve a better solvent selection, various solvents such as dimethylformamide (DMF), gamma-butyrolactone (GBL), methyl-2-pyrrolidinone (NMP), dimethyl sulfoxide (DMSO), DMF-DMSO, GBL-DMSO, and NMP-DMSO that were well known as the most representative and effective solvent for perovskite precursor solvents were chosen, and they were all investigated and compared comprehensively on the basis of cell performances, quantum efficiencies, charge transport behaviors, intermediate-phase formation, and perovskite film morphology. These comparative investigations revealed that the DMF-DMSO can raise the device performances in planar-structured perovskite devices more largely than other solvents. More notably, an excellent power conversion efficiency of 15.05% with no distinct hysteresis was produced from the PSCs with DMF-DMSO. This approach will be a meaningful step toward a better solvent design for the realization of better-performing planar perovskite solar devices.

To demonstrate fully brush-painted planar heterojunction perovskite solar cells (PeSCs), poly (3,4-ethylendioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL), CH3NH3PbI3 perovskite photoactive layer, and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) electron acceptor layer are successively brush-painted. In particular, correlation between morphology of perovskites and overall performance of PeSCs are investigated depending on the perovskites precursor. Devices with brush-painted perovskite using generally used N,N-dimethylformamide (DMF) solvent show poor performance and large deviation in cell-performance. However, PeSCs with brush-painted perovskite employing protic 2-Methoxyethanol (2-M) as DMF-alternative solvent exhibit comparable power conversion efficiency (PCE) of 9.08% to conventional spin-coated device and excellent reproducibility in device performance is observed as well. Furthermore, a fully brush-painted PeSC based on flexible substrates, showing PCE of 7.75%, is successfully demonstrated.

Although highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has emerged as alternative transparent electrodes to indium thin oxide (ITO), cell-performance is inferior to ITO based polymer solar cells (PSCs). To improve PEDOT:PSS based PSCs, we inserts metal-oxide hole transport layer (HTL) between PEDOT:PSS electrodes and photoactive layers for the first time. Device with optimized vanadium oxide HTL exhibits enhanced power conversion efficiency (PCE) of 3.33% (3.03% for conventional ITO-free PSCs). Improved performance is attributed to the increased shunt resistance and reduced surface roughness of PEDOT:PSS electrodes. Furthermore, improvement in device-stability under the atmospheric condition is observed.

We present an efficient and stable interfacial material based on a water-soluble perylene diimide derivative functionalized with ionic and methacrylate groups (abbreviated as PDIM), which can be stabilized by the photo-polymerization of diacrylate groups at both ends of the side chain in the PDIM. The characteristics of the photo-cross-linked PDIM films were examined using absorption spectra, cyclic voltammetry, work function, and surface morphology. The feasibility of the photo-cross-linked PDIM films as a novel electron transporting layer (ETL) in polymer solar cells (PSCs) was also investigated. The PTB7-Th:PC71BM-based PSC using the PDIM as the ETL achieved the excellent power conversion efficiency of 9.44% similar to the conventional polyethylenimine ethoxylated (PEIE) and better than ZnO. Furthermore, the PSC with the PDIM films exhibited a similar lifetime to that of the PEIE-based device. This approach suggests that the photo-cross-linked PDIM film could be regarded as a promising interfacial material for fabricating highly efficient PSCs.

We report characteristics of MoO3 graded ITO anodes prepared by a RF/DC graded sputtering for acidic poly(3,4-ethylene dioxylene thiophene):poly(styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs). Graded sputtering of the MoO3 buffer layer on top of the ITO layer produced MoO3 graded ITO anodes with a sheet resistance of 12.67 Ω/square, a resistivity of 2.54 × 10−4 Ω cm, and an optical transmittance of 86.78%, all of which were comparable to a conventional ITO anode. In addition, the MoO3 graded ITO electrode showed a greater work function of 4.92 eV than that (4.6 eV) of an ITO anode, which is beneficial for hole extraction from an organic active layer. Due to the high work function of MoO3 graded ITO electrodes, the acidic PEDOT:PSS-free OSCs fabricated on the MoO3 graded ITO electrode exhibited a power conversion efficiency 3.60% greater than that of a PEDOT:PSS-free OSC on the conventional ITO anode. The successful operation of PEDOT:PSS-free OSCs indicates simpler fabrication steps for cost-effective OSCs and elimination of interfacial reactions caused by the acidic PEDOT:PSS layer for reliable OSCs.

We investigated a graphene oxide (GO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) composite as a promising candidate for the practical application of a 2-D carbonaceous hole transport layer (HTL) to planar heterojunction perovskite solar cells (PeSCs) consisting of a transparent electrode/HTL/perovskite/fullerene/metal electrode. Both the insulating properties of GO and the non-uniform coating of the transparent electrode with GO cause the poor morphology of perovskite induced low power conversion efficiency (PCE) of 6.4%. On the other hand, PeSCs with a GO/PEDOT:PSS composite HTL, exhibited a higher PCE of 9.7% than that of a device fabricated with conventional PEDOT:PSS showing a PCE of 8.2%. The higher performance is attributed to the decreased series resistance (RS) and increased shunt resistance (RSh). The well-matched work-function between GO (4.9 eV) and PEDOT:PSS (5.1 eV) probably results in more efficient charge transport and an overall decrease in RS. The existence of GO with a large bandgap of ∼3.6 eV might induce the effective blocking of electrons, leading to an increase of RSh. Moreover, improvement in the long-term stability under atmospheric conditions was observed.

We demonstrate that an easily accessible polyacrylonitrile (PAN) polymer can efficiently function as a novel solution-processable anode interfacial layer (AIL) to boost the device performances of polymer:fullerene-based solar cells (PSCs). The PAN thin film was simply prepared with spin-coating of a cost-efficient PAN solution dissolved in dimethylformamide on indium tin oxide (ITO), and the thin polymeric interlayer on PSC parameters and stability were systemically investigated. As a result, the cell efficiency of the PSC with PAN was remarkably enhanced compared to the device using bare ITO. Furthermore, with PAN, we finally achieved an excellent power conversion efficiency (PCE) of 6.7% and a very high PSC stability in PTB7:PC71BM systems, which constitute a highly comparable PCE and superior device lifetime relative to those of conventional PSCs with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PSS). These results demonstrate that the inexpensive solution-processed PAN polymer can be an attractivePSS alternative and is more powerful for achieving better cell performances and lower cost PSC production.

Imperfection originating from the ionic nature of organic inorganic hybrid perovskite (OIHP) is a major factor that degrades perovskite solar cells (PSCs) performance, and mitigating or removing it is essential for the implementation of high-performance PSCs. In this work, 2-hydroxyethyl acrylate (HEA), having both effective C O and O–H functional groups, is introduced as a functional additive that suppress imperfections by to control the crystallization process and passivate them at the same time, and the role of each function groups have been systematically investigated. We have found that O–H functional groups of HEA strongly interacts with organic cations (i.e., MABr, FAI) to form more stable organic cation-HEA complex selectively, delaying the crystallization process of perovskite. As a result, HEA improves crystallinity and grain size of perovskite and reduces charge trapping density by passivation and/or suppression of defect states. HEA raises average cell-efficiency from 17.37% to 19.01% and the maximum efficiency is reached to 21.01% for the inverted planar PSC. In addition, large-area (1.08 cm2) PSCs show an excellent efficiency of 20.40%, which is the highest efficiency in large-area inverted planar PSCs to date. PSCs with HEA also show long-term stability and better moisture resistance capabilities in ambient air conditions.

Carbon quantum dots (CQDs) have attracted extreme interest as a promising nanocarbon platform for divergence optoelectronics due to their high stability, good dispersibility in solvents, and tunable optical and electronic properties. Herein, planar p-i-n type perovskite solar cells (PSCs) with enhanced efficiency and long-term stability were developed by incorporating CQDs into a nickel oxide (NiO) hole transport layer (HTL). The incorporation of CQDs downshifts the band structure of NiO, leading to good alignment with the work-function of the tin-doped indium oxide (ITO) electrode and the band-edges of the perovskite. The efficient cascade charge transport achieved with the optimized incorporation ratio of CQDs resulted in an enhanced power conversion efficiency (PCE) of 17.02%, compared to that of the PSC fabricated with bare NiO (15.66%), even though they were fabricated in air. The suppressed charge recombination accompanied by restricted charge accumulation curtails the J-V hysteresis, with a reduction from 4.5% to less than 1%. Moreover, long-term stability under atmospheric conditions without any encapsulation was achieved with CQD-incorporated NiO. More than 70% of the initial PCE was retained over 190 h. This work suggests a novel strategy for fabricating solution-processible metal oxide interlayers with highly efficient charge migration for divergence energy conversion devices.

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.

Highly transparent and stretchable Ag nanowire (NW)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid electrodes were prepared on stretchable polyurethane substrates by using simple and cost-effective brush painting technique. The optimized Ag NW/PEDOT:PSS hybrid electrode showed a sheet resistance of 19.7 Ohm/square and a high optical transmittance of 88.64% comparable to conventional ITO electrode. It was found that shear stress of the paintbrush led to an effective lateral alignment of the Ag NWs into the PEDOT:PSS matrix during brush painting process. In addition, we investigated mechanical properties of the brush painted Ag NW/PEDOT:PSS hybrid electrode using inner/outer bending test, stretching tests, twisting test and rolling test in detail. The optimized brush painted Ag NW/PEDOT:PSS electrode showed a higher strain (~30%) than brush painted Ag NW or sputtered ITO electrode. Furthermore, we demonstrated the outstanding stretchability of brush painted Ag NW/PEDOT:PSS hybrid electrode in two applications: stretchable interconnectors and stretchable electrodes for stretchable and wearable thin film heaters. These results provide clear evidence for its potential and widespread applications in next-generation, stretchable displays, solar cells, and electronic devices.

MoS2 counter electrodes obtained via spin-coating of MoS2 nanosheets followed by thermal treatment at varied temperatures were used as highly transparent counter electrodes in dye-sensitized solar cells, and the effect of temperatures on electrocatalytic activity as well as overall power conversion efficiency (PCE) of DSSCs was investigated. DSSC with thermally treated MoS2 at 100 °C exhibited comparable PCE of 7.35% to conventional Pt contained DSSC showing 7.53%, whereas cell performance with MoS2 thermally treated at higher temperature over 300 °C showed significant decrease in PCE due to the chemical change of MoS2 to poor electrocatalytic MoO3.

The spray process is compatible with the roll-to-roll process, which has the highest productivity and the lowest costs among the developed processing techniques. In this study, we demonstrated a technique involving the spraying of a secondary solvent after the formation of an active layer, by using a spray process with a relatively lowboiling- point solution. With this technique, we obtained the much smoother surface topography and more ordered bulk heterojunction morphology through enhanced self-organization of the composite materials. Consequently, the device with additionally sprayed high-boiling-point solvent allowed to achieve fill factor (FF) and power conversion efficiency (PCE) values as high as 67% and 3.76%, respectively.

Enhanced cell-efficiency of inverted bulk-heterojunction based polymer solar cells (PSCs) was achieved by anode modification with reduced graphene oxide (rGO). The rGO thin film was obtained with spin-coating of a cost-effective rGO solution dissolved in ethanol on top of the organic photoactive layer, and the effects of the rGOs as a new interlayer on device-performances of inverted-structure PSCs were investigated. The inverted PSC with r-GO showed a remarkable enhancement in power conversion efficiency compared with the cells with no interfacial layers. In particular, the inverted device with r-GO showed highly comparable efficiencies and superior PSC-stability to conventional PEDOT:PSS-based inverted PSCs.

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.

As an alternative hole transport layer (HTL) to poly(3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), we investigated V2O5 thin films fabricated by simple brush painting without any post-treatments. Polymer solar cells (PSCs) with V2O5 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 RS is obtained; thus, the resulting device shows higher performance. PSC with brush painted V2O5 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 V2O5 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 V2O5 based PSC to over 60% after exposure in air for 96 h without any encapsulation).

We demonstrate that radiation-induced reduced graphene oxide (RrGO) can efficiently function as a hole transporting layer (HTL) for polymer solar cells (PSCs). The solution-processable RrGO was simply obtained by γ-ray irradiation of a graphene oxide (GO) solution dispersed in ethanol and water. Changes in the chemical composition, conductivity, work-function, and morphology in RrGO films that resulted from the increase in absorbed dose amounts were systematically investigated. In addition, GO, a conventional hydrazine-based GO (CRGO), and the RrGOs were also studied as HTLs in PSCs, and as a result, the RrGO-based PSC showed more enhanced PSC performance than those of GO and CRGO due to better conductivity than GO and better film morphology and work function than CRGO. More importantly, the best RrGO-based PSC showed comparable cell performance to the conventional poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-based PSC and better stability than PEDOT:PSS, indicating that the use of the RrGO is more desirable as an efficient HTL than the PEDOT:PSS for high-performance and high-stability PSCs.

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.

a b s t r a c t Polymer solar cells (PSCs) with a structure of transparent electrodes/moderately reduced graphene oxide (GO)/active layer/LiF/Al were fabricated, in which moderately reduced GO serves as a hole transport layer (HTL). The GO based HTLs were prepared using spray process, which is one of the most promising methods to demonstrate cost-efficient high speed mass production of PSCs, on hot substrate fixed at various temperatures of 100, 200, 300, and 400 ◦ C, respectively. Power conversion efficiencies (PCEs) of PSCs with sprayed GO HTLs were gradually increased as the temperature of substrate was going up and in particular PSC including sprayed GO at the highest temperature, 400 ◦

To use as counter electrode in dye-sensitized solar cells (DSSCs) highly transparent graphene oxide (GO)–Pt composite film was fabricated via spin-coating of synthesized GO followed by pulse current (PC) electrodeposition of Pt, which has many benefits such as controlling of particle size and density, remarkable adhesion, uniform morphology, and simple and atmospheric pressure method without any use of vacuum systems. Compared to GO counter electrode, uniform distribution of Pt nanoparticles with a size of ~ 30 nm on GO leads to dramatic improvement of electrocatalytic activity toward the I3− + 2e− = 3I− reaction, and thus overall power conversion efficiency was increased from 3.99% to 7.10%. Moreover, GO–Pt composite counter electrode showed superior characteristics to PC electrodeposited Pt counter electrode showing ununiform distribution of Pt nanoparticles on rough fluorine-doped tin oxide (FTO) coated glass substrates.

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.

A r-GO with sulfonic acid groups (sr-GO) was newly developed and it showed dramatically concentrated aqueous dispersions with high film conductivity. With the aid of sulfonic acid groups, good compatibility with various HOMO materials was achieved, resulting in PCEs over 7% for sr-GO-based cells with superior device stability to PEDOT:PSS-based devices.

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.

A one-step reduction and functionalization of graphene oxide (FrGO) was easily achieved using a novel phenylhydrazine-based reductant containing fluorine atoms, which can induce p-type doping due to its high electronegativity. The FrGO-based OPV exhibited a high power conversion efficiency of ∼6.71% and a superior OPV-stability to commercial PEDOT:PSS.

Efficient inverted polymer solar cells (PSCs) were fabricated with ZnO electron transport layers (ETLs) prepared by spray pyrolysis, which is a simple and cost efficient method producing a thin oxide layer by direct spray of precursor on hot substrate. To investigate the effect of substrate temperature on the structural and optical properties as well as performance of PSCs, ZnO ETLs were fabricated by spray pyrolysis on hot substrate controlled at 150, 250, and 350 °C, respectively. The PSC with ZnO prepared by spray pyrolysis at 150 °C exhibited poor power conversion efficiency (PCE) of 0.94% due to the mis-matched energy level and microscopic roughness of ZnO ETL. On the other hand, enhanced efficiency of 2.99% and 3.22% was obtained by using ZnO prepared by spray pyrolysis at 250 and 350 °C, respectively. Enhancement of efficiency at higher temperature is attributed to better matching of ZnO coated ITO work-function with the lowest unoccupied molecular orbital (LUMO) energy level of PCBM and the formation of smooth and homogeneous polycrystalline ZnO, resulting in improved interfacial property and electron transport. In the durability test, inverted ZnO solar cell was retained above 80% during 9 days in an ambient atmosphere without any encapsulation, while conventional solar cells showed dramatic decrease of efficiency.

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.

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.

Moderately reduced graphene oxide (GO) films were fabricated by simple and fast thermal treatment of solution processed GO, and their application as an alternative to conventional Pt counter electrode in dye-sensitized solar cells (DSSCs) was investigated. GO without thermal treatment and thermally treated GO at 150 °C showed low efficiency of ∼0.5%, whereas cell performance was significantly improved by applying thermal treatment over 250 °C. In particular, the DSSC with GO thermally treated at 350 °C exhibited the highest performance with open-circuit voltage ( V OC ) of 0.66 V, short-circuit current density ( J SC ) of 16.35 mA/cm 2 , F.F. of 33.33%, and overall power conversion efficiency (PCE) of 3.60%. Moderate reduction of GO by simple thermal treatment over 250 °C was confirmed through the measurements of X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Enhancement of efficiency after high temperature thermal treatment might be attributed to the improved electrical conductivities and higher catalytic activities, resulting from the reduction of GO.

Background Hyaluronic acid (HA) dermal biphasic fillers are synthesized for their efficacy in correcting aesthetic defects such as wrinkles, scars and facial contouring defects. The fillers consist of crosslinked HA microspheres suspended in a noncrosslinked HA. To extend the duration of HAs within the dermis and obtain the particle texturing feel, HAs are crosslinked to obtain the suitable mechanical properties. Results Hyaluronic acid (HA) dermal biphasic fillers are prepared by mixing the crosslinked HA microspheres and the noncrosslinked HAs. The elastic modulus of the fillers increased with raising the volume fraction of the microspheres. The mechanical properties and the particle texturing feel of the fillers made from crosslinked HA (1058 kDa) microspheres suspended in noncrosslinked HA (1368 kDa) are successfully achieved, which are adequate for the fillers. Conclusions Dermal biphasic HA fillers made from 1058 kDa exhibit suitable elastic moduli (211 to 420 Pa) and particle texturing feel (scale 7 ~ 9).

In the present study, a novel polar-solvent vapor annealing (PSVA) was used to induce a significant structural rearrangement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films in order to improve their electrical conductivity and work function. The effects of polar-solvent vapor annealing on PEDOT:PSS were systematically compared with those of a conventional solvent additive method (SAM) and investigated in detail by analyzing the changes in conductivity, morphology, top and bottom surface composition, conformational PEDOT chains, and work function. The results confirmed that PSVA induces significant phase separation between excess PSS and PEDOT chains and a spontaneous formation of a highly enriched PSS layer on the top surface of the PEDOT:PSS polymer blend, which in turn leads to better 3-dimensional connections between the conducting PEDOT chains and higher work function. The resultant PSVA-treated PEDOT:PSS anode films exhibited a significantly enhanced conductivity of up to 1057 S cm(-1) and a tunable high work function of up to 5.35 eV. The PSVA-treated PEDOT:PSS films were employed as transparent anodes in polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs). The cell performances of organic optoelectronic devices with the PSVA-treated PEDOT:PSS anodes were further improved due to the significant vertical phase separation and the self-organized PSS top surface in PSVA-treated PEDOT:PSS films, which can increase the anode conductivity and work function and allow the direct formation of a functional buffer layer between the active layer and the polymeric electrode. The results of the present study will allow better use and understanding of polymeric-blend materials and will further advance the realization of high-performance indium tin oxide (ITO)-free organic electronics.

To increase the efficiency of TiO 2 nanotube-based dye-sensitized solar cells, we fabricated TiO 2 nanotubes and decorated them with ZnO rod-like nanostructures via anodization of Ti metal sheets followed by the hydrothermal growth of ZnO. Compared to conventionally anodized nanotubes, the modified nanotubes provided a higher specific surface area for dye adsorption. Besides increased dye adsorption, suppression of the recombination of photo-induced electrons at the electrode/electrolyte interface was observed in the modified nanotube-based systems because of the existence of a ZnO thin layer on the surface of nanotubes. This thin layer was applied as a seed for an oriented growth of ZnO. Dye-sensitized solar cells based on TiO 2 nanotubes decorated with ZnO rod-like nanostructures showed a higher power conversion efficiency of 3.84%, compared to standard nanotube devices with an efficiency of 2.06%.

One of the attractions of solution-processed polymer solar cells (PSCs) is the potential for low-cost production by high-throughput roll-to-roll processes. The spray process can be suggested as an elegant alternative for PSCs fabrication due to its high production speed. We highlight the effects of sprayed droplet sizes on the film topography and drying time of droplets. We relate the latter to the PSCs device performances. The transfer efficiency and deposition rate of the spray process as a function of the droplet size are investigated for the high production speed and lowering the cost. PSC device fabrication with an optimized spray-operating condition yielded a power conversion efficiency of 3.4%. The comparable efficiency of PSCs fabricated by a roll-to-roll compatible process compared to spin-coated one achieved in this paper brings these devices one step closer to the realization of low-cost PSCs production.

Highly efficient and cost-effective polymer solar cells (PSCs) based poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) have been fabricated by inkjet-printing with various additives. All solution-processed layers in the solar cells—a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer and a photoactive layer based on P3HT and PCBM with additives—were inkjet-printed. The device performance is strongly influenced by the addition of high boiling point additives in the photoactive ink with chlorobenzene (CB) solvent. The morphology, optoelectronic properties, and overall solar cell performance of the devices were dramatically affected by additives, such as 1,8 octanedithiol (ODT), o-dichlorobenzene (ODCB) and chloronaphthalene (Cl-naph). A device fabricated from ink formulated with ODT exhibited the best overall performance with power conversion efficiency (PCE) of 3.71%.