Enhanced Device Performances of MAFACsPb(IxBr1-x) Perovskite Solar Cells with Dual-Functional 2-Chloroethyl Acrylate Additives.

Perovskite photovoltaics (PePVs) tend to suffer from a high density of defects that restrict the device in terms of performances and stability. Therefore, defect passivation and film-quality improvement of perovskite active layers are crucial for high-performance PePVs. In this work, 2-chloroethyl acrylate (CEA) with C═O and -Cl groups in Cs0.175FA0.750MA0.075Pb (I0.880Br0.120) precursor solutions is introduced as a novel bifunctional additive to act as both a defect passivator and perovskite-growth controller. With the aid of CEA, the perovskite crystallinity and average grain size are improved, and perovskite defects are effectively reduced, thus increasing the representative efficiency (PCE = 19.32%). PePVs with CEA also maintain their initial efficiency of 85% even after about 500 h under air conditions with a humidity of 40 ± 5%. As a result, this study proves that the novel additive CEA can produce higher PePV efficiency and more stable devices.

Beyond Fullerenes: Indacenodithiophene-Based Organic Charge-Transport Layer toward Upscaling of Low-Cost Perovskite Solar Cells.

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.

Hysteresis data of planar perovskite solar cells fabricated with different solvents.

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]).

Brush-paintable and highly stretchable Ag nanowire and PEDOT:PSS hybrid electrodes.

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.

Photo-cross-linked perylene diimide derivative materials as efficient electron transporting layers in inverted polymer solar cells.

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.

Effect of molecular weight of hyaluronic acid (HA) on viscoelasticity and particle texturing feel of HA dermal biphasic fillers.

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).

Graphene oxide/PEDOT:PSS composite hole transport layer for efficient and stable planar heterojunction perovskite solar cells.

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.

Efficient PEDOT:PSS-Free Polymer Solar Cells with an Easily Accessible Polyacrylonitrile Polymer Material as a Novel Solution-Processable Anode Interfacial Layer.

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) ( PEDOT: PSS). These results demonstrate that the inexpensive solution-processed PAN polymer can be an attractive PEDOT: PSS alternative and is more powerful for achieving better cell performances and lower cost PSC production.

Planar heterojunction perovskite solar cells with superior reproducibility.

Perovskite solar cells (PeSCs) have been considered one of the competitive next generation power sources. To date, light-to-electric conversion efficiencies have rapidly increased to over 10%, and further improvements are expected. However, the poor device reproducibility of PeSCs ascribed to their inhomogeneously covered film morphology has hindered their practical application. Here, we demonstrate high-performance PeSCs with superior reproducibility by introducing small amounts of N-cyclohexyl-2-pyrrolidone (CHP) as a morphology controller into N,N-dimethylformamide (DMF). As a result, highly homogeneous film morphology, similar to that achieved by vacuum-deposition methods, as well as a high PCE of 10% and an extremely small performance deviation within 0.14% were achieved. This study represents a method for realizing efficient and reproducible planar heterojunction (PHJ) PeSCs through morphology control, taking a major step forward in the low-cost and rapid production of PeSCs by solving one of the biggest problems of PHJ perovskite photovoltaic technology through a facile method.

An approach for an advanced anode interfacial layer with electron-blocking ability to achieve high-efficiency organic photovoltaics.

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.

Fluorine-functionalized and simultaneously reduced graphene oxide as a novel hole transporting layer for highly efficient and stable organic photovoltaic 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.

Significant vertical phase separation in solvent-vapor-annealed poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) composite films leading to better conductivity and work function for high-performance indium tin oxide-free optoelectronics.

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.