Comparison of Optical and Electrical Properties of Different Hole-Transporting Materials for Solution-Processable Organic Light-Emitting Diodes.

Achieving well-defined multilayer structure is a key to improve device performance of organic light-emitting diodes (OLEDs), especially in solution-processed OLEDs. Use of cross-linkable hole-transporting materials (HTMs) is therefore gaining much attention to achieve such multilayer structures. One of representative solution-processable HTM is TFB, poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)], but it does not have any cross-linkable units in its chemical structures. In this work, we performed basic physical characterization of a new cross-linkable HTM, HL-X026, and we also investigated its OLED characteristics. Actual solvent resistance by varying the thermal curing temperatures was measured. The thermally cross-linkable HL-X026 showed better device performances than simple TFB with higher luminance and efficiencies.

Interfacial Modifier Having Julolidine for the Cathode Buffer Layer in PTB-7:PC70BM Based Inverted Organic Photovoltaic Cells.

The julolidine based interfacial modifier (IM-J) for cathode buffer layer following the "donor-acceptor" design concept with julolidine substituent as an electron donating moiety was incoporated to improve the surface properties of ZnO. Simple treatment of metal oxide type cathode buffer materials with organic interfacial modifier induces the enhanced photovoltaic performance and could effectively overcome several interfacial problems in inverted organic photovoltaic cells (I-OPVs). We studied on the coverage of IM-J on ZnO surface with variation of solution concentrations to reduce charge recombination and macroscopic phase separation. At the optimum condition, ZnO/IM-J (0.05 w/v%), IM-J significantly decreased the surface tension (46.1 mN/m) and improved surface morphology (RMS roughness: 0.61 nm). As a result, compared to the unmodified ZnO based device, the ZnO/IM-J based I-OPVs showed significantly improved power conversion efficiency (PCE) from 7.41 to 8.07% due to the increased photocurrent density (Jsc) and fill factor (FF). It is concluded that IM-J is one of the promising candidates for controlling electronic property of ZnO buffer layer in inverted organic photovoltaic cells. Also, our interfacial modified system can be utilized in other optoelectronic devices.

Syntheses of D-A-A Type Small Molecular Donor Materials Having Various Electron Accepting Moiety for Organic Photovoltaic Application.

Small molecular donor, DTDCTB achieved a high power conversion efficiency (PCE) value of 6.6 ± 0.2% in vacuum-deposited planar mixed heterojunction (PMHJ) structure. However, the same material just recorded PCE of 0.34% in solution processed small molecule based bulk heterjunction (BHJ) organic photovoltaic cells. For the improvement of organic photovoltaic cells (OPVs), In this study, we designed and synthesized several D-A-A (donor-acceptor-acceptor) type molecular electron donating materials. Ditolylaminothienyl moiety as an electron donating group connected to 1,2,5-benzothiadiazole as a conjugated electron accepting unit, simultaneously with an electron accepting terminal group such as cyano alkyl acetate and N-alkyl rhodanine. The thermal, photophysical, and electrochemical properties of prepared small molecules were investigated by DSC, UV/Vis spectroscopy and Cyclic Voltametry, respectively. As a result, 0.89% of PCE can be obtained from OPV using a mixture of DTATBTER and PCBM as an active layer with a Voc of 0.87 V, a Jsc of 3.20 mA/cm2, and a fill factor of 31.9%.

Solution Processed Organic Photovoltaic Cells Using D-A-D-A-D Type Small Molecular Donor Materials with Benzodithiophene and Diketopyrrolopyrrole Units.

Organic photovoltaic Cells (OPVs) have been considered to be a next-generation energy source to overcome exhaustion of resources. Currently, OPVs are developed based on two types of donor material with polymer and small molecule. Polymeric donor materials have shown better power conversion efficiency (PCE) than small molecular donor materials, since it's easy to control the morphology of photoactive film. However, the difficulty in synthetic reproducibility and purification of polymeric donor were main drawback to overcome. And then, recently small molecule donor materials have been overcome bad morphology of OPVs film by using appropriate alkyl substituents and relatively long conjugation system. In this study, we designed and synthesized D-A-D-A-D type small molecular donor materials containing alternatively linked benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) units. Also, we studied on the effect of photovoltaic performance of prepared small molecular D-A-D-A-D type donor with variation of thiophene links and with/without hexyl substituent. Our small molecular donors showed HOMO energy levels from -5.26 to -5.34 eV and optical bandgaps from 1.70 to 1.87 eV by CV (cyclic voltammetry) and UV/Vis spectroscopy, respectively. Finally, 3.4% of PCE can be obtained using a mixture of BDT(DPP)2-T2 and PCBM as an active layer with a Voc of 0.78 V, a Jsc of 9.72 mA/cm2, and a fill factor of 0.44 under 100 mW/cm2 AM 1.5G simulated light. We will discuss the performance of D-A-D-A-D type small molecular donor based OPVs with variation of both terminal substituents.

A new prognostic model for chemotherapy-induced febrile neutropenia.

BACKGROUND: The objective of this study was to develop and validate a new prognostic model for febrile neutropenia (FN). METHODS: This study comprised 1001 episodes of FN: 718 for the derivation set and 283 for the validation set. Multivariate logistic regression analysis was performed with unfavorable outcome as the primary endpoint and bacteremia as the secondary endpoint. RESULTS: In the derivation set, risk factors for adverse outcomes comprised age ≥ 60 years (2 points), procalcitonin ≥ 0.5 ng/mL (5 points), ECOG performance score ≥ 2 (2 points), oral mucositis grade ≥ 3 (3 points), systolic blood pressure <90 mmHg (3 points), and respiratory rate ≥ 24 breaths/min (3 points). The model stratified patients into three severity classes, with adverse event rates of 6.0 % in class I (score ≤ 2), 27.3 % in class II (score 3-8), and 67.9 % in class III (score ≥ 9). Bacteremia was present in 1.1, 11.5, and 29.8 % of patients in class I, II, and III, respectively. The outcomes of the validation set were similar in each risk class. When the derivation and validation sets were integrated, unfavorable outcomes occurred in 5.9 % of the low-risk group classified by the new prognostic model and in 12.2 % classified by the Multinational Association for Supportive Care in Cancer (MASCC) risk index. CONCLUSIONS: With the new prognostic model, we can classify patients with FN into three classes of increasing adverse outcomes and bacteremia. Early discharge would be possible for class I patients, short-term observation could safely manage class II patients, and inpatient admission is warranted for class III patients.

High Detectivity Near Infrared Organic Photodetectors Using an Asymmetric Non-Fullerene Acceptor for Optimal Nanomorphology and Suppressed Dark Current.

Recently, the development of non-fullerene acceptors (NFAs) for near-infrared (NIR) organic photodetectors (OPDs) has attracted great interest due to their excellent NIR light absorption properties. Herein, we developed NFAs by substituting an electron-donating moiety (branched alkoxy thiophene (BAT)) asymmetrically (YOR1) and symmetrically (YOR2) for the Y6 framework. YOR1 exhibited nanoscale phase separation in a film blended with PTB7-Th. Moreover, substituting the BAT unit effectively extended the absorption wavelengths of YOR1 over 1000 nm by efficient intramolecular charge transfer and extension of the conjugation length. Consequently, YOR1-OPD exhibited significantly reduced dark current and improved responsivity by simultaneously satisfying optimal nanomorphology and significant suppression of charge recombination, resulting in 1.98 × 1013 and 3.38 × 1012 Jones specific detectivity at 950 and 1000 nm, respectively. Moreover, we successfully demonstrated the application of YOR1-OPD in highly sensitive photoplethysmography sensors using NIR light. This study suggests a strategic approach for boosting the overall performance of NIR OPDs targeting a 1000 nm light signal using an all-in-one (optimal morphology, suppressed dark current, and extended NIR absorption wavelength) NFA.

Synthesis and characterization of conjugated low band-gap terpolymers incorporating carbazole for photovoltaic application.

A series of photoactive conjugated low band-gap copolymer (CPSB) and terpolyemrs (TPSBCz-n, n = 1 to 4) based on N-alkyl carbazole, 4,4'-dialkyl dithienosilole, and bezothiadiazole were synthesized. The copolymer and terpolymers were built with the fraction of the carbazole unit varied for 0, 2.5, 5, 10 and 25 mol%. Among the mixtures, the composition of 25 wt% of terpolymer bearing 10 mol.% of the carbazole unit, TPSBCz-3, and 75 wt% of C71-PCBM found a power conversion efficiency of 0.86% with a open-circuit voltage of 0.59 V, the short-circuit current of 4.85 mA and fill factor of 0.30 under AM 1.5 spectral illumination. Our findings suggest that terpolymer bearing low concentration of carbazole lead to a high power conversion efficiency with improved the short-circuit current due to hole mobility enhancement effect of carbazole unit.

Synthesis of fluorene-based semiconducting copolymers for organic solar cells.

Semiconducting polymers composed of 2,2'-(9,9-dioctyl-9H-fluorene-2,7-diyl)dithiophenes (F8T2s) and (2E,2'E)-3,3'-(2,5-bis(octyloxy)-1,4-phenylene) bis(2-(5-bromothiophene-2-yl)acrylonitrile)s (OPTANs) have been synthesized through Pd(O)-catalyzed Suzuki coupling polymerization by controlling the monomer ratio. The synthesized polymers were confirmed to exhibit good solubility in common solvents, simple processability, and thermal stability up to 350 degrees C. The highest occupied molecular orbitals (HOMOs), lowest unoccupied molecular orbitals (LUMOs), and optical band-gap energies were determined using cyclic voltammetry (CV) and UV-visible spectrometry. The synthesized polymers showed their maximum absorption and edge at around 520 and 650 nm, respectively. The optical band-gap energies of the polymers were determined to be 1.89 eV. Bulk heterojunction organic solar cells were fabricated using the conjugated polymer as the electron donor, and 6,6-phenyl C61-butyric acid methylester (PC61BM) or 6,6-phenyl C71-butyric acid methylester (PC71BM) as the electron acceptor. The power conversion efficiencies (PCEs) of the solar cells based on polymer:PC71BM (1:1) and polymer:PC71BM (1:2) were 0.68% and 1.22%, respectively, under air mass 1.5 global (AM 1.5 G) illumination at 100 mW/cm2.

Preparation and characterization of high molecular weight low bandgap polymers based on poly(2,7-carbazole)s for organic solar cells.

We report the PCDTBT {Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]}, an alternating copolymer of 2,7-carbazole and dithienyl-2,1,3-benzothiazole, has high molecular weight and narrow molecular weight distribution. Our PCDTBT can be successfully prepared as good yield by using tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] catalyst instead of Pd2dba3/P(o-Tol)3 catalyst. From the UV/Vis absorption spectroscopy, we can observe that absorption bands of PCDTBT are bathochromically shifted by increasing the molecular weight, that is to say, our high molecular weight PCDTBT can absorb much longer wavelength light compare to low molecular weight PCDTBT. The best performance can be obtained from device based on the mixture of PCDTBT (polymer-30) and PC70BM {[6,6]-phenyl C71-butyric acid methyl ester} (1:4) as an active layer, which shows 4.50% of PCE with 10.1 mA/cm2 of short-circuit current density (J(SC)), 0.85 V of open-circuit voltage (V(OC)), and 52.3% of fill factor which is very similar with Leclerc's published result.

Stretchable graphene transistors with printed dielectrics and gate electrodes.

With the emergence of human interface technology, the development of new applications based on stretchable electronics such as conformal biosensors and rollable displays are required. However, the difficulty in developing semiconducting materials with high stretchability required for such applications has restricted the range of applications of stretchable electronics. Here, we present stretchable, printable, and transparent transistors composed of monolithically patterned graphene films. This material offers excellent mechanical, electrical, and optical properties, capable of use as semiconducting channels as well as the source/drain electrodes. Such monolithic graphene transistors show hole and electron mobilities of 1188 ± 136 and 422 ± 52 cm(2)/(V s), respectively, with stable operation at stretching up to 5% even after 1000 or more cycles.

Highly Sensitive and Durable Organic Photodiodes Based on Long-Term Storable NiOx Nanoparticles.

Organic optoelectronic devices that can be fabricated at low cost have attracted considerable attention because they can absorb light over a wide frequency range and have high conversion efficiency, as well as being lightweight and flexible. Moreover, their performance can be significantly affected by the choice of the charge-selective interlayer material. Nonstoichiometric nickel oxide (NiOx) is an excellent material for the hole-transporting layer (HTL) of organic optoelectronic devices because of the good alignment of its valence band position with the highest occupied molecular orbital level of many p-type polymers. Herein, we report a simple low-temperature process for the synthesis of NiOx nanoparticles (NPs) that can be well dispersed in solution for long-term storage and easily used to form thin NiOx NP layers. NiOx NP-based organic photodiode (OPD) devices demonstrated high specific detectivity (D*) values of 1012-1013 jones under various light intensities and negative biases. The D* value of the NiOx NP-based OPD device was 4 times higher than that of a conventional poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based device, an enhancement that originated mainly from the 16 times decreased leakage current. The NiOx NP-based OPD device demonstrated better reliability over a wide range of light intensities and operational biases in comparison to a device with a conventional sol-gel-processed NiOx film. More importantly, the NiOx NP-based OPD showed long-term device stability superior to those of the PEDOT:PSS and sol-gel-processed NiOx-based devices. We highlight that our low-temperature solution-processable NiOx NP-based HTL could become a crucial component in the fabrication of stable high-performance OPDs.

Synthesis and characterization of new dithienosilole-based copolymers for polymer solar cells.

A series of dithienosilole-based copolymers, poly [(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-5,5'-diyl] (P1), poly[(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,2'-bithiazole)-5,5'-diyl] (P2), poly[(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2, 6-diyl-alt-(10 -methyl-phenothiazine)-3,7-diyl](P3), poly[(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-9,10-anthracene)-5,5'-diyl] (P4) were synthesized by the Pd-catalyzed Stille polymerization method. Electron-deficient benzothiadiazole and bithiazole units and electron-rich phenothiazine and anthracene moieties were incorporated into the polymer backbone to obtain the broad absorption spectrum and to improve the hole-transporting characteristics, respectively. The polymer solar cell (PSC) was fabricated with a layered structure of ITO/PEDOT:PSS/polymer:C71-PCBM (1:3)/LiF/Al. The best performance of PSC was obtained at P3:C71-PCBM which reaches a power conversion efficiency (PCE) of 1.18%, with a short circuit current density (J(sc)) of 4.75 mA/cm2, an open circuit voltage (V(oc)) of 0.71 V, and a fill factor (FF) of 0.35 under AM 1.5G irradiation (100 mW/cm2).

Synthesis of a new conjugated polymer composed of pyrene and bithiophene units for organic solar cells.

An alternating conjugated copolymer composed of pyrene and bithiophene units, poly(DHBT-alt-PYR) has been synthesized. The synthesized polymer was found to exhibit good solution processibility and thermal stability, losing less than 5% of their weight on heating to approximately 370 degrees C. The synthesized polymer showed its maximum absorption and peak PL emission at 401 and 548 nm, respectively. The optical band gap energy of the polymer was determined by absorption onset to be 2.64 eV. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the polymer was determined to be -5.48 and -2.84 eV by cyclic voltametry (CV) and the optical band gap. The polymer photovoltaic devices were fabricated with a typical sandwich structure of ITO/PEDOT:PSS/active layer/LiF/Al using poly(DHBT-alt-PYR) as an electron donor and C60-PCBM or C70-PCBM as electron acceptors. The open circuit voltage, short circuit current and fill factor of the device using C70-PCBM as an acceptor were 0.75 V, 3.80 mA/cm2 and 0.28, respectively, and the maximum power conversion efficiency of the device was 0.80%.

Synthesis and properties of copolymers composed of arylenevinylene and phenothiazine for organic solar cells.

A series of new organic semiconducting copolymers composed of {(2E,2'E)-3,3'-[2,5-bis(octyloxy)-1,4-phenylene]-bis[2-(thiophen-2-yl)acrylonitrile]}(OPTAN) and 10(2'-ethylhexylphenothiazine) (PTZ) monomers, (the copolymers are hereafter referred to as poly(OPTAN-co-PTZ)s), were synthesized by using Suzuki coupling polymerization in which the monomer ratios were controlled. An increase in the OPTAN content shifted the peak and onset absorption of the copolymers to the longer wavelength regions, which resulted in a decrease in the band gap energy. The maximum UV absorption of the polymer films was in the range 523-540 nm and the optical band gap energies were in the range 1.90-1.87 eV. Energy levels of the highest occupied molecular orbital (HOMO) of the polymers were determined by cyclic voltammetry (CV). The HOMO energy level of the copolymers was between -5.07 and -5.12 eV. Photovoltaic devices were fabricated by using the copolymers as the p-type donor and C60-PCBM or C70-PCBM as the electron acceptors. The device with poly(50OPTAN-alt-50PTZ) and C70-PCBM showed the best performance among the fabricated devices; the open circuit voltage, short circuit current, fill factor, and maximum power conversion efficiency of this device were 0.79 V, 5.25 mA/cm2, 0.30, and 1.25%, respectively.

Recent progress of ultra-narrow-bandgap polymer donors for NIR-absorbing organic solar cells.

Solution-processed near-infrared (NIR)-absorbing organic solar cells (OSCs) have been explored worldwide because of their potential as donor:acceptor bulk heterojunction (BHJ) blends. In addition, NIR-absorbing OSCs have attracted attention as high specialty equipment in next-generation optoelectronic devices, such as semitransparent solar cells and NIR photodetectors, owing to their feasibility for real-time commercial application in industry. With the introduction of NIR-absorbing non-fullerene acceptors (NFAs), the value of OSCs has been increasing while organic donor materials capable of absorbing light in the NIR region have not been actively studied yet compared to NIR-absorbing acceptor materials. Therefore, we present an overall understanding of NIR donors.

Enhanced Static and Dynamic Properties of Highly Miscible Fullerene-Free Green-Selective Organic Photodetectors.

We developed p-n junction organic photodetectors (OPDs) composed of a polymer donor and a nonfullerene acceptor (NFA) to increase both the responsivity (R) and detectivity (D*) while maintaining a narrow wavelength selectivity. The selection of the polymer donor and NFA with similar green (G) absorption is important for achieving G-wavelength selectivity in these OPDs, which differentiates them from current fullerene-based OPDs and NFA-based panchromatic absorption OPDs. In addition, mixing the polymer donor and asymmetric NFA was efficient toward increasing the miscibility and decreasing the interfacial energy difference of the blended films, resulting in the formation of a uniform and well-mixed nanomorphology in the photoconductive layer. Two-dimensional (2D) grazing incidence X-ray diffraction and Fourier-transform infrared spectroscopy revealed that the lamellar ordering of the polymer donor was enhanced in the blend film prepared with an asymmetric NFA, whereas the aggregation of a symmetric NFA in the blend films did not increase the lamellar ordering of the polymer donor. Consequently, we achieved an R value of 0.31 A/W and D* value of 2.0 × 1013 Jones with a full width at half-maximum value of 230 nm at -2 V and fast response time of 27 µs without any external bias in the asymmetric NFA-based OPDs. The enhancement in the lamellar ordering and miscibility of the blended films are crucial toward increasing the static and dynamic properties of OPDs.

Layer-by-layer assembled multilayer TiO(x) for efficient electron acceptor in polymer hybrid solar cells.

We demonstrate that TiO(x) nanocomposite films fabricated using electrostatic layer-by-layer (LbL) assembly improve the power conversion efficiency of photovoltaic cells compared to conventional TiO(x) films fabricated via the sol-gel process. For this study, titanium precursor/poly(allylamine hydrochloride) (PAH) multilayer films were first deposited onto indium tin oxide-coated glass to produce TiO(x) nanocomposites (TiO(x)NC). The specific effect of the LbL processed TiO(x) on photovoltaic performance was investigated using the planar bilayer TiO(x)NC and highly regioregular poly(3-hexylthiophene) (P3HT) solar cells, and the P3HT/LbL TiO(x)NC solar cells showed a dramatic increase in power efficiency, particularly in terms of the short current density and fill factor. The improved efficiency of this device is mainly due to the difference in the chemical composition of the LbL TiO(x)NC films, including the much higher Ti(3+)/Ti(4+) ratio and the highly reactive facets of crystals as demonstrated by XPS and XRD measurement, thus enhancing the electron transfer between electron donors and acceptors. In addition, the grazing incidence wide-angle X-ray scattering (GIWAXS) study revealed the presence of more highly oriented P3HT stacks parallel to the substrate on the LbL TiO(x)NC film compared to those on the sol-gel TiO(x) films, possibly influencing the hole mobility of P3HT and the energy transfer near and at the interface between the P3HT and TiO(x) layers. The results of this study demonstrate that this approach is a promising one for the design of hybrid solar cells with improved efficiency.

Orthogonal Printable Reduced Graphene Oxide 2D Materials as Hole Transport Layers for High-Performance Inverted Polymer Solar Cells: Sheet Size Effect on Photovoltaic Properties.

Creating an orthogonal printable hole-transporting layer (HTL) without damaging the underlying layer is still a major challenge in fabricating large-area printed inverted polymer solar cells (PSCs). In this study, we prepared orthogonal-processable fluorine-functionalized reduced graphene oxide (FrGO) series with various two-dimensional sheet sizes such as large-sized FrGO (1.1 µm), medium-sized FrGO (0.7 µm), and small-sized FrGO (0.3 µm) and systematically investigated the size effect of FrGOs on the hole transport properties of PSCs. The FrGOs exhibit highly stable dispersion without change over 90 days in 2-propanol solvent, indicating very high dispersion stability. Decreasing the sheet size of FrGOs enhanced hole-transporting properties, resulting in power conversion efficiencies (PCEs) of 9.27 and 9.02% for PTB7-Th:EH-IDTBR- and PTB7-Th:PC71BM-based PSCs, respectively. Compared to devices with solution-processed poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), a 14% enhancement of PCEs was achieved. Interestingly, the PCEs of devices with the smallest FrGO sheet are higher than the PCE of 8.77% of a device with vacuum-deposited MoO3. The enhancement in the performance of PSCs is attributed to the enhanced charge collection efficiency, decreased leakage current, internal resistance, and minimized charge recombination. Finally, small-sized FrGO HTLs were successfully coated on the photoactive layer using the spray coating method, and they also exhibited PCEs of 9.22 and 13.26% for PTB7-Th:EH-IDTBR- and PM6:Y6-based inverted PSCs, respectively.

Composite Interlayer Consisting of Alcohol-Soluble Polyfluorene and Carbon Nanotubes for Efficient Polymer Solar Cells.

We report the synthesis of composite interlayers using alcohol-soluble polyfluorene (ASP)-wrapped single-walled carbon nanotubes (SWNTs) and their application as electron-transport layers for efficient organic solar cells. The ASP enables the individual dispersion of SWNTs in solution. The ASP-wrapped SWNT solutions are stable for 54 days without any aggregation or precipitation, indicating their very high dispersion stability. Using the ASP-wrapped SWNTs as a cathode interlayer on zinc oxide nanoparticles (ZnO NPs), a power conversion efficiency of 9.45% is obtained in PTB7-th:PC71BM-based organic solar cells, which is mainly attributed to the improvement in the short circuit current. Performance enhancements of 18 and 17% are achieved compared to those of pure ZnO NPs and ASP on ZnO NPs, respectively. In addition, the composite interlayer is applied to non-fullerene-based photovoltaics with PM6:Y6, resulting in a power conversion efficiency of up to 14.37%. The type of SWNT (e.g., in terms of diameter range and length) is not critical to the improvement in the charge-transport properties. A low density of SWNTs in the film (∼1 SWNTs/µm2 for ASP-wrapped SWNTs) has a significant influence on the charge transport in solar cells. The improvement in the performance of the solar cell is attributed to the increased internal quantum efficiency, balanced mobility between electrons and holes, and minimized charge recombination.

A study on the photopolymerization of acrylic monomers having fluorene moiety for the application of holographic data storage system.

We have prepared photopolymer compositions for holographic data storage system from aromatic diacrylate having fluorine moiety, a hybrid sol-gel, and photoinitiator. The fluorenyl diacrylate monomer was synthesized via nucleophilic substitution reaction of fluorene diphenol with an excess of 2-chloroethoxyethanol, followed by the reaction with acryloyl chloride. The physical and holographic properties of photopolymer were controlled by the ratio of precursor triethoxysilylpropyl polyethyleneglycol carbamate (TSPEG) in a hybrid sol-gel binder and the content of monomer. Also, we measured the photopolymerization rate and conversion of monomer by photo-differential scanning calorimeter (photo-DSC). Holographic recording was attempted by photopolymerization of the monomers in the photopolymer film using a 532 nm laser light in the presence of Irgacure 784 and holographic gratings were recorded into the photopolymer films by interfering two collimated plane wave beams. Contents of monomer and TSPEG were changed in the range of 0.25-1.0 equiv. and the composition were optimized in terms of diffraction efficiency. Finally, we obtained that efficient photopolymer films showed diffraction efficiency of 78% when 0.5 equiv. of TESPEG in sol-gel binder and 40% of compound 4 were added.