We report on light-emitting diodes (LEDs) made from blend polymers composed of two organic soluble and emittable conducting polymers, poly[2-methoxy-5-(2-ethylhexyloxy-1,4-phenylenevinylene] (MEH-PPV) and poly[1,3-propanedioxy-1,4-phenylene-1,2-ethenylene(2,5-bis(trimethylsilyl)-1,4phenylene)-1,2-ethenylene-1,4-phenylene] (DSiPV), as the emitting layers. The emitting colors of the blend polymers were yellowish orange, which indicates that the emission is mainly due to MEH-PPV and DSiPV greatly contributes to the enhancement of the luminescence. The efficiencies of the blend polymers increase with decreasing MEH-PPV/DSiPV weight ratio. In blending MEH-PPV with DSiPV, DSiPV is believed to serve as an EL enhancing polymer rather than EL active in our devices. The quantum efficiency is measured as the function of MEH-PPV content in the blend. Especially, the maximum quantum efficiency of MEH-PPV/DSiPV(1/15) blend polymer is about 500 times greater than that of MEH-PPV homopolymer, and the luminance is up to 500 cd/m 2 at 30 V with 23.6 mA/cm 2 current density.

Light emission from pale blue to greenish blue is successfully obtained from the diodes made of the trimethylsilyl-, monoalkoxy-, and dialkoxy-substituted polymers with welldefined conjugation length containing phenylenevinylene units. The conjugation length is adjusted by incorporating the nonconjugated spacer group in the backbone. The polymers are organic soluble and allow the fabrication of the light-emitting diode by spinning without further thermal processes. The fabricated devices show typical diode characteristics with operation voltages of 15-20 V, and the light is visible at the current density of about less than 0.5 mA/cm* 12 345for all three devices. The electroluminescence spectra are similar to the photoluminescence spectra and show the red shift as the electron-donation effects of the substituents become stronger. The bluest color of light emission corresponds to 470 nm for the polymer with trimethylsilyl substituent.

We designed and synthetized a new poly{4,8-bis ((2-ethylhexyl)The optical bandgap of PTTBDT-FTT was 1.55 eV. The energy levels of the highest occupied and lowest unoccupied molecular orbitals of PTTBDT-FTT were −5.31 and −3.73 eV, respectively. Two-dimensional grazing-incidence X-ray scattering measurements showed that the film's PTTBDT-FTT chains are predominantly arranged with a face-on orientation with respect to the substrate, with strong π−π stacking. An organic thin-film transistor fabricated using PTTBDT-FTT as the active semiconductor showed high hole mobility of 2.1 × 10 −2 cm 2 /(V•s). Single-junction bulk heterojunction photovoltaic cells with the configuration ITO/PEDOT:PSS/PTTBDT-FTT:PC 71 BM/Ca/Al were fabricated, which showed a maximum power conversion efficiency (PCE) of 7.44%. Inverted photovoltaic cells with the structure ITO/PEIE/PTTBDT-FTT:PC 71 BM/MoO 3 /Ag were also fabricated, with a maximum PCE of 7.71%. A tandem photovoltaic device comprising the inverted PTTBDT-FTT:PC 71 BM cell and a P3HT:ICBA-based cell as the top and bottom cell components, respectively, showed a maximum PCE of 8.66%. This work demonstrated that the newly developed PTTBDT-FTT polymer was very promising for applications in both single and tandem solar cells. Furthermore, this work highlighted the fact that an extended π-system in the electron-donor moiety in low bandgap polymers is crucial for improving polymer solar cells.

There has been growing interest in organic thin-film transistors (OTFTs) because of their potential applications in flexible, low-cost integrated circuits, such as smart cards, RF identification tags, and display backplanes, such as liquid crystal displays, electronic paper, and organic electroluminescent displays. [1,2] In particular, since organic semiconductors based on polymers and oligomers are attractive for their easy solution processing for film formation, recent research on OTFTs has been more focused on flexible electronic devices/display applications. Therefore, the most desired ultimate goal of organic semiconductor devices is to realize flexible electronics and displays that can be processed through all-solution processes including deposition of the active organic layers, the gate insulators, and the electrodes. Here we demonstrate all-solutionprocessed n-type organic transistors for the first time by depositing the source and drain metal by a spinning metal process.Despite the great interest and progress in organic and polymeric TFTs, most of the high field-effect-mobility OTFTs have been based on p-type channel materials. However, even if n-channel semiconducting materials are important for making ambipolar transistors [3,4] and complementary circuits, [5] they are relatively rare compared with the p-type materials. The reported field-effect mobilities of n-type OTFTs to date also show lower values than those of p-type devices. In addition, it has usually been observed that the solution-processed OTFTs show poorer performance than the vacuum-processed devices: for example, although the vacuum-evaporated pentacene transistor has shown high field-effect hole mobilities exceeding 1 cm 2 V ±1 s ±1 , [6] the solution-processed p-type transistor using the pentacene precursor showed low fieldeffect mobilities below 0.1 cm 2 V ±1 s ±1 . [7] Reports about the solution-processed n-type transistors are also relatively rare [5,8±10] and they usually show low charge-carrier mobilities (~10 ±2 cm 2 V ±1 s ±1 or less) [5,8,10,11] except that most recently the observation of a field-effect electron mobility as high as 0.1 cm 2 V ±1 s ±1 for a solution spin-coated conjugated ladder polymer was reported.[9] Here we report on solution-processed n-type OTFTs with high field-effect mobilities, based on the soluble derivatives of fullerene (C 60 ) as n-type channel materials. We obtained high field-effect electron mobilities of 0.02±0.1 cm 2 V ±1 s ±1 depending on the work-function of the source and drain metals, demonstrating that the electron injection current is contact-limited because of the Schottky barrier at the contact. Furthermore, we fabricated n-type OTFTs by an all-solution-deposition process including source and drain metals as well as gate insulators and organic semiconductors. These types of OTFTs are well suited for a wide range of existing and future flexible circuits and display applications that require a simplified production process and low-weight and low-cost products. In order to achieve the solu...

We have synthesized a new p-type polymer, poly(9,9‘-n-dioctylfluorene-alt-biselenophene) (F8Se2), via the palladium-catalyzed Suzuki coupling reaction. The number-average molecular weight (M n) of F8Se2 was found to be 72 600. F8Se2 dissolves in common organic solvents such as chloroform and chlorobenzene. The PL emission peak of a film of F8Se2 is clearly red-shifted with respect to that of its sulfur analogue, poly(9,9‘-n-dioctylfluorene-alt-bithiophene) (F8T2), due to the electron-donating properties of selenium and the strong interactions between the biselenophene moieties in neighboring copolymer chains. We confirmed that F8Se2 is a thermotropic liquid crystalline polymer with an aligned structure by carrying out DSC, PLM, and XRD measurements. The introduction of the selenophene moiety into the liquid-crystalline polymer system results in better field-effect transistor (FET) performance than that of F8T2. A solution-processed F8Se2 FET device with a bottom contact geometry was found to exhibit a hole mobility of 0.012 cm2/(V s) and a low threshold voltage of −4 V, which is the one of the highest solution-processable FET performances.

A highly processable, new semiconducting polymer, PCDTTz, based on alternating thiazolothiazole and carbazole units was synthesized. The new polymer exhibited a field-effect carrier mobility of up to 3.8 × 10(-3) cm(2) V(-1) s(-1) and bulk heterojunction solar cells made from PCDTTz produced a power conversion efficiency of 4.88% under AM 1.5 G (100 mW cm(-2)) conditions.

Two semiconducting conjugated polymers were synthesized via Stille polymerization. The structures combined unsubstituted or (triisopropylsilyl)ethynyl (TIPS)-substituted 2,6-bis(trimethylstannyl)benzo[1,2-b:4.5-b']dithiophene (BDT) as a donor unit and benzotriazole with a symmetrically branched alkyl side chain (DTBTz) as an acceptor unit. We investigated the effects of the different BDT moieties on the optical, electrochemical, and photovoltaic properties of the polymers and the film crystallinities and carrier mobilities. The optical-band-gap energies were measured to be 1.97 and 1.95 eV for PBDT-DTBTz and PTIPSBDT-DTBTz, respectively. Bulk heterojunction photovoltaic devices were fabricated and power conversion efficiencies of 5.5% and 2.9% were found for the PTIPSBDT-DTBTz- and PBDT-DTBTz-based devices, respectively. This difference was explained by the more optimal morphology and higher carrier mobility in the PTIPSBDT-DTBTz-based devices. This work demonstrates that, under the appropriate processing conditions, TIPS groups can change the molecular ordering and lower the highest occupied molecular orbital level, providing the potential for improved solar cell performance.

Solution-processable semiconducting copolymers, poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5′-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and poly [4,8-bis(2-ethylhexyl-2-thenyl)-benzo[1,2-b:4,5-b′]dithiophene-alt-5,5′-(4′,7′-di-2thienyl-2′,1′,3′-benzothiadiazole)] (PBDTDTBT), and their pyrene-containing terpolymers were synthesized using Suzuki or Stille coupling. Pyrene units were introduced to improve the chargetransporting abilities of the polymers. The resulting polymers were found to be soluble in common organic solvents and formed smooth and uniform spin-coated thin films. They also exhibited good thermal stability and lost <5% of their weight upon heating to ∼350 °C. Solution-processed field-effect transistors fabricated using these polymers showed p-type organic thin-film transistor characteristics. The pyrene-containing terpolymers showed higher field-effect mobilities than their corresponding parent polymers, and their mobility increased with increasing pyrene content. Furthermore, they had lower HOMO energy levels than the corresponding PCDTBT or PBDTDTBT polymers. Bulk heterojunction solar cells with an ITO/PEDOT:PSS/ polymer:PC 71 BM/Ca/Al configuration fabricated using the pyrene-containing polymers had higher power conversion efficiencies than those using the corresponding parent polymers.