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The capacitance-voltage (C-V) characterization of polymer light-emitting diodes (PLEDs) employing poly[5-(2'-ethylexyloxy)-2-methoxy-1,4-phenylene vinylene], as light-emitting layer is discussed. Several metals, such as calcium, aluminum, and gold were used as the cathode in order to investigate the influence of the charge injection on the C-V characteristics.

Device characteristics of polymer based bulk-heterojunction photovoltaic cells incorporating poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] and methanofullerene ([6,6]-phenyl C61-butyric acid methyl ester) as the active materials are examined as a function of active layer thickness. The dependence of short circuit current on optical effects and its oscillatory variation on the polymer layer thickness is explained by solving the short circuit current using the drift-diffusion equations, where the light intensity calculated from the optical transfer matrix theory is used as the input for optical carrier generation. Furthermore, the effects of polymer layer thickness on other device operation parameters such as open-circuit voltage, fill factor, and series resistivity are measured. Considering the variation of above mentioned parameters, an optimized power conversion efficiency as high as 1.8% (under simulated air mass 1.5 global conditions) was achieved for a device with a polymer layer thickness of 55 nm. [ABSTRACT FROM AUTHOR]

Regioregular poly(3-hexylthiophene) (RR-P3HT) is a promising candidate for polymer photovoltaic research due to its stability and absorption in the red region. In this manuscript, we report polymer photovoltaic devices based on RR-P3HT:methanofullerene [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) 1:1 weight-ratio blend. We studied the effects of annealing temperature and time on the device performance for devices annealed before and after cathode deposition. Thermal annealing shows significant improvement in the performance for both types of annealing conditions, with postproduction annealing being slightly better. For devices with a 43-nm-thick active layer, maximum power conversion efficiency (PCE) of 3.2% and fill factor up to 67% is achieved under Air Mass 1.5, 100-mW/cm2 illumination. We performed atomic force microscopy and ultraviolet-visible absorption spectroscopy on the P3HT:PCBM films to explain the effect of thermal annealing. By keeping the optimized thermal annealing condition and by varying the active layer thickness, we fabricated devices with PCE up to 4.0%, which is the highest efficiency reported so far for this system. [ABSTRACT FROM AUTHOR]

Converting solar energy into electricity provides a much-needed solution to the energy crisis the world is facing today. Polymer solar cells have shown potential to harness solar energy in a cost-effective way. Significant efforts are underway to improve their efficiency to the level of practical applications. Here, we report highly efficient polymer solar cells based on a bulk heterojunction of polymer poly(3-hexylthiophene) and methanofullerene. Controlling the active layer growth rate results in an increased hole mobility and balanced charge transport. Together with increased absorption in the active layer, this results in much-improved device performance, particularly in external quantum efficiency. The power-conversion efficiency of 4.4% achieved here is the highest published so far for polymer-based solar cells. The solution process involved ensures that the fabrication cost remains low and the processing is simple. The high efficiency achieved in this work brings these devices one step closer to commercialization. [ABSTRACT FROM AUTHOR]

The article focuses on the advancement of polymer solar cells (PSCs) and its various applications such as consolidation into textiles or as rollable charging pads for portable electronics. It notes several advantages of PSCs including low-cost fabrication of large-area devices, low specific-weight, and mechanical flexibility. It notes the applicability of PSCs to be integrated into various textiles and fabrics for use in clothing, wallpaper, and curtains.

We compare organic donor/acceptor heterojunction photovoltaic devices based on copper phthalocyanine (CuPc) as the donor and [6,6]-phenyl C60 butyric acid methyl ester (PCBM) or buckminsterfullerene (C60) as the acceptor. The effect of the two acceptors on open-circuit voltage and short-circuit current density is studied. Improved interface properties, optimal energy level matching, and more balanced charge transport are believed to be the reasons for better performance of CuPc/PCBM heterojunction device, in terms of photocurrent and fill factor. The energy conversion efficiency of the devices under AM1.5G solar illumination at 130 mW/cm2 is improved to 1.18%, up from 0.74%. [ABSTRACT FROM AUTHOR]

We demonstrate bilayer source-drain (S-D) electrodes for organic thin film transistors (OTFT). The bilayer consists of a transition metal oxide (MoO3,WO3, or V2O5) layer and a metal layer. The metal oxide layer, directly contacting the organic semiconducting layer, serves as the charge-injection layer. The overcoated metal layer is responsible for the conduction of charge carriers. We found that the metal oxide layer coupled between pentacene and metal layers played an important role in improving the field-effect transistor characteristics of OTFTs. Devices with the bilayer S-D electrodes showed enhanced hole-injection compared to those with only metal electrode. High field-effect mobility of 0.4 cm2/V s and on/off current ratios of 104 were obtained in the pentacene based TFTs using the bilayer S-D electrodes at a gate bias of -40 V. The improvement is attributed to the reduction in the contact barrier and the prevention of metal diffusion into the organic layer and/or unfavorable chemical reaction between the organic layer and the metal electrode. [ABSTRACT FROM AUTHOR]

We report organic solar cells fabricated with small-molecule organic semiconductor tetracene/C60 heterojunction as the photoactive layer. The external power conversion efficiency of the devices under AM 1.5 solar illumination at 100 mW/cm2 (1 sun) is 2.3±0.5% with relatively high open-circuit voltage (Voc=0.58±0.06 V) compared to most of the other small-molecular donor-acceptor (D-A) heterojunction solar cells reported so far. Using atomic force microscopy and x-ray diffraction we found that tetracene thin films consist of submicron-sized grains with rough surface and well defined molecular order. Therefore, using high mobility polycrystalline tetracene thin films for D-A heterojunction devices dramatically increases area of tetracene and C60 interface for exciton diffusion to reduce the recombination. [ABSTRACT FROM AUTHOR]