Effect of fluorine on the photovoltaic properties of 2,1,3-benzothiadiazole-based alternating conjugated polymers by changing the position and number of fluorine atoms.

Fluorination is one of the most effective ways to manipulate molecular packing, optical bandgap and molecular energy levels in organic semiconductor materials. In this work, different number of fluorine atoms was introduced into the acceptor moiety 2,2'-dithiophene linked 2,1,3-benzothiadiazole, utilizing the alkylthiophene modified dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b] (DTBDT) as the donor unit, three polymers: PDTBDT-0F-BTs, PDTBDT-2F-BTs and PDTBDT-6F-FBTs were synthesized. With the number of fluorine atoms in each repeat unit of polymers varying from 0 to 2 and then up to 6, PDTBDT-0F-BTs, PDTBDT-2F-BTs and PDTBDT-6F-FBTs exhibited gradually downshifted energy levels and improved dielectric constants (εr) from 3.4 to 4.3 to 5.8, further successively increased charge transport mobilities. As a result, the power conversion efficiency (PCE) of the bulk heterojunction organic photovoltaic devices (BHJ-OPV) from the blend films of aforementioned polymers paired with PC71BM were gradually increased from 1.69 for PDTBDT-0F-BTs to 1.89 for PDTBDT-2F-BTs and then to 5.28 for PDTBDT-6F-FBTs. The results show that the continuous insertion of fluorine atoms into the repeating units of the benzothiadiazole conjugated polymer leads to the deepening of HOMO energy level, the increase of εr and the increase of charge mobility, which improve the efficiency of charge transfer and electron collection, thus improving the photovoltaic performance of BHJ-OPV.

Interfacial Engineering by VOx/m-TiO2 Films for Optimizing Photon-Generated Carrier to Boost Photoelectrochemical N2 Conversion to NH3.

Optimal design of the photocathode is crucial and a meaningful approach for regulating many important photoelectrochemical (PEC) reactions. Interfacial engineering is substantiated as an effective tactic for tuning the direction of the internal carrier flow in thin-film semiconductor solar devices. Yet, so far, the type of PV device architecture involving in the interfacial transport layer is less adopted in photoelectrochemical (PEC) devices. Herein, the coupled VOx/TiO2 interfacial engineering brings in the construction of an integrated p-ZnTe hetero-structured photocathode, which was composed of a PN junction constructed with p-ZnTe and CdS, VOx as the interface layer for hole transport, and m-TiO2 as the scaffold layer. Compared with the simple PN structure, the photocathodes with the assembly of interfacial engineering enable advances in the combination of apparent quantum efficiency (AQE: 0.6%) and better yield (6.23 µg h-1 cm-2) on photoelec-N2 conversion to NH3. Interfacial engineering and heterojunction construction effects synergistically optimize photoexcited carriers and the separation and transformation at the interface. This favors easier migration of holes to the back and the assembly of electrons on the surface, achieving the intensive charge separation and surface charge injection efficiency of photogenerated carriers. Our work represents a new enlightenment for building thin-film photocathode architectures to boost the effectiveness on solar-driven utilization.

Novel Alcohol-Soluble Nitroxide Radical Conjugated Polymer for Cathode Modifier of Efficient Organic Solar Cells with Enhanced Stability.

Alcohol-soluble conjugated polymers with polar side-chain components have been regarded as one of the most promising cathode interfacial modifers (CIMs) to achieve high-performance organic solar cells (OSCs). Herein, a novel alcohol-soluble nitrogen oxide radical conjugated polymer (PBN-NO) containing dimethylamine groups for regulating metal work function and the dangling of 2,2,6, 6-tetramethylpiperidine 1-oxy (TEMPO) radical side-chain groups for theoretically improving the conductivity, was prepared and characterized. As compared to the OSCs from PM6:Y6 blends with the most common CIMs of PFN, PDINO, and PDINN, the OSCs with PBN-NO as CIMs provide better or comparable power conversion efficiencies (PCEs) (16.19% vs 13.10%, 15.60%, and 16.15%), enhanced photostability, and thermal stability. Besides that, the reasons for the improving PCEs of the OSCs with PBN-NO modifier are systematically investigated and supported by a set of comparative experiments such as exciton dissociation, charge recombination, capacitance-voltage (C-V), etc. To the best of our knowledge, this is the first report of an alcohol-soluble nitroxide radical conjugated polymer that successfully integrates the interfacial modification of polar groups and improves conductivity by dangling radicals, therefore contributing to efficient OSCs with enhanced stability.

A Nitroxide Radical Conjugated Polymer as an Additive to Reduce Nonradiative Energy Loss in Organic Solar Cells.

Nonfullerene-acceptor-based organic solar cells (NFA-OSCs) are now set off to the 20% power conversion efficiency milestone. To achieve this, minimizing all loss channels, including nonradiative photovoltage losses, seems a necessity. Nonradiative recombination, to a great extent, is known to be an inherent material property due to vibrationally induced decay of charge-transfer (CT) states or their back electron transfer to the triplet excitons. Herein, it is shown that the use of a new conjugated nitroxide radical polymer with 2,2,6,6-tetramethyl piperidine-1-oxyl side groups (GDTA) as an additive results in an improvement of the photovoltaic performance of NFA-OSCs based on different active layer materials. Upon the addition of GDTA, the open-circuit voltage (VOC ), fill factor (FF), and short-circuit current density (JSC ) improve simultaneously. This approach is applied to several material systems including state-of-the-art donor/acceptor pairs showing improvement from 15.8% to 17.6% (in the case of PM6:Y6) and from 17.5% to 18.3% (for PM6:BTP-eC9). Then, the possible reasons behind the observed improvements are discussed. The results point toward the suppression of the CT state to triplet excitons loss channel. This work presents a facile, promising, and generic approach to further improve the performance of NFA-OSCs.

Two Compatible Acceptors as an Alloy Model with a Halogen-Free Solvent for Efficient Ternary Polymer Solar Cells.

A ternary strategy of halogen-free solvent processing can open up a promising pathway for the preparation of polymer solar cells (PSCs) on a large scale and can effectively improve the power conversion efficiency with an appropriate third component. Herein, the green solvent o-xylene (o-XY) is used as the main solvent, and the non-fullerene acceptor Y6-DT-4F as the third component is introduced into the PBB-F:IT-4F binary system to broaden the spectral absorption and optimize the morphology to achieve efficient PSCs. The third component, Y6-DT-4F, is compatible with IT-4F and can form an "alloy acceptor", which can synergistically optimize the photon capture, carrier transport, and collection capabilities of the ternary device. Meanwhile, Y6-DT-4F has strong crystallinity, so when introduced into the binary system as the third component can enhance the crystallization, which is conducive to the charge transport. Consequently, the optimal ternary system based on PBB-F:IT-4F:Y6-DT-4F achieved an efficiency of 15.24%, which is higher than that of the binary device based on PBB-F:IT-4F (13.39%).

Multistep Functional Embellishment for p-ZnTe as a Cathode to Boost the Faraday Efficiency of Nitrogen Conversion.

An electrochemical N2 reduction reaction (N2RR) is a selective sustainable approach to obtain NH3 at mild conditions and has been proposed as an alternative to the full-blown Haber-Bosch process. However, achieving high yields of NH3 and high faraday efficiency (FE) at a low overpotential remains a big challenge but has high expectations for the electrocatalytic N2RR. Herein, a novel p-ZnTe cathode multistep embellished with NiOx and ZnO thin films was prepared for boosting faraday efficiency to 9.89% for N2RR at -0.2 V vs reversible hydrogen electrode (RHE), about 12 times of p-ZnTe@ZnO. All components within the NiOx@p-ZnTe/ZnO electrode work cooperatively. A N source was determined through a 15N isotopic-labeling experiment. Using steady-state photoluminescence, electrochemical impedance spectroscopy, and control experiments, a possible model of charge transformation is built. In particular, a NiOx layer has an important impact on increasing interfacial contact between a bare fluorine-doped tin oxide (FTO) glass and p-ZnTe and further reinforcing interfacial electron transfer. This work provides a practical application and a feasible strategy to develop highly efficient catalysts for N2 reduction and also affords a guideline for the fabrication of a flat electrode.

Significantly Boosting Efficiency of Polymer Solar Cells by Employing a Nontoxic Halogen-Free Additive.

Traditional additives like 1,8-diiodooctane and 1-chloronaphthalene were successfully utilized morphology optimization of various polymer solar cells (PSCs) in an active layer, but their toxicity brought by halogen atoms limits their corresponding large-scale manufacturing. Herein, a new nontoxic halogen-free additive named benzyl benzoate (BB) was introduced into the classic PSCs (PTB7-Th:PC71BM), and an optimal power conversion efficiency (PCE) of 9.43% was realized, while there was a poor PCE for additive free devices (4.83%). It was shown that BB additives could inhibit PC71BM's overaggregation, which increased the interface contact area and formed a better penetration path of an active layer. In addition, BB additives could not only boost the distribution of a PTB7-Th donor at the surface, beneficial to suppressing exciton recombination in inverted devices but also boost the crystallinity of a blend layer, which is conducive to exciton dissociation and charge transport. Our work effectively improved a device performance by using a halogen-free additive, which can be referential for industrialization.

An Alternating Copolymer Derived from Indolo[3,2-b]carbazole and 4,7-Di(thieno[3,2-b]thien-2-yl)-2,1,3-benzothiadiazole for Photovoltaic Cells.

An alternating narrow bandgap conjugated copolymer (PICZ-DTBT, E(g) = 1.83 eV) derived from 5,11-di(9-heptadecanyl)indolo[3,2-b]carbazole and 4,7-di(thieno[3,2-b]thien-2-yl)-2,1,3-benzothiadiazole (DTBT), was prepared by the palladium-catalyzed Suzuki coupling reaction. The resultant polymer absorbs light from 350-690 nm, exhibits two absorbance peaks at around 420 and 570 nm and has good solution processibility and thermal stability. The highest occupied molecular orbital (HOMO) energy level and lowest unoccupied molecular orbital (LUMO) level of the copolymer determined by cyclic voltammetry were about -5.18 and -3.35 eV, respectively. Prototype bulk heterojunction photovoltaic cells from solid-state composite films based on PICZ-DTBT and [6,6]-phenyl-C(71) butyric acid methyl ester (PC(71) BM), show power conversion efficiencies up to 2.4% under 80 mW · cm(-2) illumination (AM1.5) with an open-circuit voltage of V(oc) = 0.75 V, a short current density of J(sc) = 6.02 mA · cm(-2) , and a fill factor of 42%. This indicates that the copolymer PICZ-DTBT is a viable electron donor material for polymeric solar cells.

Insights into Excitonic Dynamics of Terpolymer-Based High-Efficiency Nonfullerene Polymer Solar Cells: Enhancing the Yield of Charge Separation States.

Ternary copolymerization strategy is considered an effective method to achieve high-performance photovoltaic conjugated polymers. Herein, a donor-acceptor1-donor-acceptor2-type random copolymer, named PBDTNS-TZ-BDD (T1), containing one electron-rich unit alkylthionaphthyl-flanked benzo[1,2-b/4,5-b'] di-thiophene (BDTNS) as D and two electron-deficient moieties benzo[1,2-c/4,5-c']dithiophene-4,8-dione (BDD) and fluorinated benzotriazole as A, was synthesized to investigate the excitonic dynamic effect. Also, the D-A-type alternating copolymer PBDTNS-BDD (P1) was also prepared for a clear comparison. Although the UV-Vis spectra and energy levels of P1 and T1 are similar, the power conversion efficiencies (PCEs) of the related devices are 11.50% (T1/ITIC) and 8.89% (P1/ITIC), respectively. The reason for this is systematically investigated and analyzed by theoretical calculation, photoluminescence, and pump-probe transient absorption spectroscopy. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculation results show that the terpolymer T1 with a lower exciton binding energy and a longer lifetime of spontaneous luminescence can synergistically increase the number of excitons reaching the donor/acceptor interface. The results of the pump-probe transient absorption spectroscopy show that the yield of charge separation of T1/ITIC is higher than that of the P1/ITIC blend film, and improved PCE could be achieved via copolymerization strategies. Moreover, the fabrication of the T1-based device is also simple without any additive or postprocessing. Therefore, it provides a promising and innovative method to design high-performance terpolymer materials.

Enhanced Organic Photovoltaic Performance through Modulating Vertical Composition Distribution and Promoting Crystallinity of the Photoactive Layer by Diphenyl Sulfide Additives.

To understand the vertical phase separation in the bulk junction active layer of organic photovoltaic devices is essential for controlling the charge transfer behavior and achieving effective charge collection. Here, diphenyl sulfide (DPS) was introduced as a novel additive into the PTB7-Th:PC71BM-based inverted polymer solar cells (PSCs), and the effect of additives on active blend films and photovoltaic characteristics was carefully studied. The results show that DPS could not only modulate the vertical composition distribution but also promote the ordered molecular packing of the photoactive layer, thus effectively improving exciton dissociation, charge transport, and collection, and thus exhibit an excellent power conversion efficiency of 9.7% with an improved fill factor (>70%) after using 3% DPS additive. The results show that the DPS solvent additive can effectively adjust the vertical phase distribution and crystallinity of blend films and improve the photovoltaic performance of the inverted organic photovoltaic devices.

Effect of Flank Rotation on the Photovoltaic Properties of Dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene-Based Narrow Band Gap Copolymers.

Side chain engineering has been an effective approach to modulate the solution processability, optoelectronic properties and miscibility of conjugated polymers (CPs) for organic/polymeric photovoltaic cells (PVCs). As compared with the most commonly used method of introducing alkyl chains, the employment of alkyl-substituted aryl flanks would provide two-dimensional (2-D) CPs having solution processability alongside additional merits like deepened highest occupied molecular orbital (HOMO) energy levels, increased absorption coefficient and charger transporting, etc. In this paper, the triple C≡C bond was used as conjugated linker to decrease the steric hindrance between the flanks of 4,5-didecylthien-2-yl (T) and dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene (DTBDT) core. In addition, an alternating CP derived from 4,5-didecylthien-2-yl-ethynyl (TE) flanked DTBDT, and 4,9-bis(4-octylthien-2-yl) naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole (DTNT), named as PDTBDT-TE-DTNT, was synthesized and characterized. As compared with the controlled PDTBDT-T-DTNT, which was derived from 4,5-didecylthien-2-yl flanked DTBDT and DTNT, the results for exciton dissociation probability, density functional theory (DFT), time-resolved photoluminescence (PL) measurements, etc., revealed that the lower steric hindrance between TE and DTBDT might lead to the easier rotation of the TE flanks, thus contributing to the decrease of the exciton lifetime and dissociation probability, finally suppressing the short-circuit current density (JSC), etc., of the photovoltaic devices from PDTBDT-TE-DTNT.

Synthesis and Photovoltaic Effect of Electron-Withdrawing Units for Low Band Gap Conjugated Polymers Bearing Bi(thienylenevinylene) Side Chains.

A novel (E)-5-(2-(5-alkylthiothiophen-2-yl)vinyl)thien-2-yl (TVT)-comprising benzo[1,2-b:4,5-b']dithiophene (BDT) derivative (BDT-TVT) was designed and synthetized to compose two donor-acceptor (D-A) typed copolymers (PBDT-TVT-ID and PBDT-TVT-DTNT) with the electron-withdrawing unit isoindigo (ID) and naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole (NT), respectively. PBDT-TVT-ID and PBDT-TVT-DTNT showed good thermal stability (360 °C), an absorption spectrum from 300 nm to 760 nm and a relatively low lying energy level of Highest Occupied Molecular Orbital (EHOMO) (-5.36 to -5.45 eV), which could obtain a large open-circuit voltage (Voc) from photovoltaic devices with PBDT-TVT-ID or PBDT-TVT-DTNT. The photovoltaic devices with ITO/PFN/polymers: PC71BM/MoO3/Ag structure were assembled and exhibited a good photovoltaic performance with a power conversion efficiency (PCE) of 4.09% (PBDT-TVT-ID) and 5.44% (PBDT-TVT-DTNT), respectively. The best PCE of a PBDT-TVT-DTNT/PC71BM-based device mainly originated from its wider absorption, higher hole mobility and favorable photoactive layer morphology.

Enhanced Photovoltaic Performance in D-π-A Copolymers Containing Triisopropylsilylethynyl-Substituted Dithienobenzodithiophene by Modulating the Electron-Deficient Units.

Three alternated D-π-A type 5,10-bis(triisopropylsilylethynyl)dithieno[2,3-d:2',3'-d']-benzo[1,2-b:4,5-b']dithiophene (DTBDT-TIPS)-based semiconducting conjugated copolymers (CPs), PDTBDT-TIPS-DTBT-OD, PDTBDT-TIPS-DTFBT-OD, and PDTBDT-TIPS-DTNT-OD, bearing different A units, including benzothiadiazole (BT), 5,6-difluorinated-BT (FBT) and naphtho[1,2-c:5,6-c']-bis[1,2,5]thiadiazole (NT), were designed and synthesized to investigate the impact of the variation in electron-deficient units on the properties of these photovoltaic polymers. It was exhibited that the down-shifted highest occupied molecular orbital energy level (EHOMO), the enhanced aggregation in both the chlorobenzene solution and the solid film, as well as the better molecular planarity, were achieved using methods involving fluorination and the replacement of BT with NT on the polymer backbone. The absorption profile was little changed upon fluorination; however, it was greatly broadened during replacement of BT with NT. Consequently, the optimized photovoltaic device based on the PDTBDT-TIPS-DTNT-OD exhibited synchronous enhancements in the open-circuit voltage (VOC) of 0.88 V, the short-circuit current density (JSC) of 7.21 mA cm-2, and the fill factor (FF) of 52.99%, resulting in a drastic elevation in the PCE by 129% to 3.37% compared to that of the PDTBDT-TIPS-DTBT-OD. This was triggered by PDTBDT-TIPS-DTNT-OD's broadened absorption, deepened EHOMO, improved coplanarity, and enhanced SCLC mobility (which increased 3.9 times), as well as a favorable morphology of the active layer. Unfortunately, the corresponding PCE deteriorated after incorporating fluorine into the BT, due to the oversized aggregation and large phase separation morphology in the blend films, severely impairing its JSC. Our preliminary results demonstrated that the replacement of BT with NT in a D-π-A type polymer backbone was an effective strategy of tuning the molecular structure to achieve highly efficient polymer solar cells (PSCs).

36% Enhanced Efficiency of Ternary Organic Solar Cells by Doping a NT-Based Polymer as an Electron-Cascade Donor.

In recent years, ternary organic photovoltaic cells (OPVs) have been dedicated to improving power conversion efficiency (PCE) by broadening optical absorption spectra. Ternary OPVs with different poly[thieno[3,2-b]thiophene-2,5-diyl-alt-4,9-bis(4-(2-decyltetradecyl)thien-2-yl)naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole-5,5'-diyl] (PTT-DTNT-DT) doping concentrations were designed and the effect of PTT-DTNT-DT as a complementary electron donor on the performance of OPVs was investigated. The optimized PCE of OPVs was increased from 3.42% to 4.66% by doping 20 wt % PTT-DTNT-DT. The remarkable improvement in the performance of the ternary device is mainly attributed to the sharp increase in the short-circuit current density and fill-factor. The major reasons have been systematically studied from atomic force microscopy, electrochemical impedance spectroscopy, surface energy, space charge limited current and photocurrent behavior. It has been found that the separation of excitons and the transportation of charge are enhanced while light absorption is increased, and the charge recombination also decreases due to the optimization of the cascade energy level and the morphology of the ternary active layer. The results show that it is feasible to improve the performance of ternary OPVs by their complementary absorption.

In Situ Growth of Metal Sulfide Nanocrystals in Poly(3-hexylthiophene): [6,6]-Phenyl C61-Butyric Acid Methyl Ester Films for Inverted Hybrid Solar Cells with Enhanced Photocurrent.

It has been reported that the performance of bulk heterojunction organic solar cells can be improved by incorporation of nano-heterostructures of metals, semiconductors, and dielectric materials in the active layer. In this manuscript, CdS or Sb2S3 nanocrystals were in situ generated inside the poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid (P3HT:PC61BM) system by randomly mixing P3HT and PC61BM in the presence of cadmium or antimony xanthate precursor. Hybrid solar cells (HSCs) with the configurations of tin-doped indium oxide substrate (ITO)/CdS interface layer/P3HT:PC61BM: x wt.% CdS/MoO3/Ag and ITO/CdS interface layer /P3HT:PC61BM: x wt.% Sb2S3/MoO3/Ag were fabricated. Hybrid active layers (P3HT:PC61BM: x wt.% CdS or P3HT:PC61BM: x wt.% Sb2S3) were formed completely by thermally annealing the film resulting in the decomposition of the cadmium or antimony xanthate precursor to CdS or Sb2S3 nanocrystals, respectively. The effects of x wt.% CdS (or Sb2S3) nanocrystals on the performance of the HSCs were studied. From UV-Vis absorption, hole mobilities, and surface morphological characterizations, it has been proved that incorporation of 3 wt.% CdS (or Sb2S3) nanocrystals in the active layer of P3HT:PC61BM-based solar cells improved the optical absorption, the hole mobility, and surface roughness in comparison with P3HT:PC61BM-based solar cells, thus resulting in the improved power conversion efficiencies (PCEs) of the devices.

Boosting Up Performance of Inverted Photovoltaic Cells from Bis(alkylthien-2-yl)dithieno[2,3-d:2',3'-d']benzo[1,2-b:4',5'-b']di thiophene-Based Copolymers by Advantageous Vertical Phase Separation.

The photovoltaic cells (PVCs) from conjugated copolymers of PDTBDT-BT and PDTBDT-FBT with 5,10-bis(4,5-didecylthien-2-yl)dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene as electron donor moieties and benzothiadiazole and/or 5,6-difluorobenzothiadiazole as electron acceptor moieties are optimized by employing alcohol-soluble PFN (poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) as cathode modification interlayer. The power conversion efficiencies (PCEs) of inverted PVCs (i-PVCs) from PDTBDT-BT and PDTBDT-FBT with devices configuration as ITO/PFN/active layer/MoO3/Ag are increased from 4.97% to 8.54% and 5.92% to 8.74%, in contrast to those for the regular PVCs (r-PVCs) with devices configuration as ITO/PEDOT:PSS/active layer/Ca/Al under 100 mW/cm2 AM 1.5 illumination. The optical modeling calculations and X-ray photoelectron spectroscopy (XPS) investigations reveal that the r-PVCs and i-PVCs from the copolymers exhibit similar light harvesting characteristics, and the enhancements of the PCEs of the i-PVCs from the copolymers are mainly contributed to the favorable vertical phase separation as the strongly polymer-enriched top surface layers and slightly PC71BM (phenyl-C71-butyric acid methyl ester)-enriched bottom surface layers are correspondingly connected to the anodes and cathodes of the i-PVCs, while they are opposite in the r-PVCs. As we known, it is the first time to experimentally verify that the i-PVCs with alcohol-soluble conjugated polymers cathode modification layers enjoy favorable vertical phase separation.

Synthesis, crystal structure and photoluminescence of 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin.

A new coumarin derivative, 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin, was synthesized and characterized by FT-IR, (1)H NMR, element analysis and single crystal X-ray crystallography. The dihedral angle of benzo[5,6]coumarin ring and phenyl group is 36.15 degrees, and the dihedral angle of phenyl group and anthracene skeleton is 89.37 degrees. The UV-vis absorption and photoluminescence of the compound were discussed. The result shown that the compound exhibits high fluorescence quantum yield (Phi(F)), large Stokes shift and green emission (508 nm). The molecular structure of the compound was optimized using density functional theory (DFT) at B3LYP/6-31G(d) level, and the HOMO and LUMO levels of the compound were deduced.

High-detectivity polymer photodetectors with spectral response from 300 nm to 1450 nm.

Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Today, gallium nitride-, silicon-, and indium gallium arsenide--based detectors are used for different sub-bands within the ultraviolet to near-infrared wavelength range. We demonstrate polymer photodetectors with broad spectral response (300 to 1450 nanometers) fabricated by using a small-band-gap semiconducting polymer blended with a fullerene derivative. Operating at room temperature, the polymer photodetectors exhibit detectivities greater than 10(12) cm Hz(1/2)/W and a linear dynamic range over 100 decibels. The self-assembled nanomorphology and device architecture result in high photodetectivity over this wide spectral range and reduce the dark current (and noise) to values well below dark currents obtained in narrow-band photodetectors made with inorganic semiconductors.

Amorphous fluorescent organic emitters for efficient solution-processed pure red electroluminescence: synthesis, purification, morphology, solid-state photoluminescence, and device characterizations.

New soluble and intrinsic amorphous red emitters 1 and 2 were obtained by Suzuki coupling. Due to the close molecular polarities, separation of target products from monocoupling impurities presents a challenge. The results showed highly pure 2 would be a potentially valuable fluorophore for solution-processed pure red electroluminescence in terms of visual sensitivity with respect to 1.