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Solution-processable non-polymeric organic semiconductors are attractive for opto-electronic applications due to their relatively simple synthetic reproducibility and characterization, and enhanced capability for fine-tuning of their properties. We report the synthesis, charge transport, photophysics, and photovoltaic properties of three non-polymeric materials based upon bisarylthiophenyl diketopyrrolopyrrole [DPP(ThAr) 2 ]. The DPP(ThAr) 2 molecules are comprised of solubilizing alkyl groups, 2-ethylhexyl (for 1a ) and 2-octyldodecyl (for 1b and 2 ), which are capped with "electron accepting" moieties - fluorenone ( 1 ) or benzothiadiazole ( 2 ). While the materials could be prepared under standard Suzuki-Miyaura cross-coupling conditions, a simple direct arylation afforded 2 and 1b in good yields. We found 1a with a short alkyl chain lacked sufficient solubility for solution processing but 1b and 2 are solution processable and form good quality films. All three materials exhibited ambipolar charge transport in field effect transistors, with 1b showing balanced charge mobilities of about 10 −3 cm 2 V −1 s −1 . Bulk heterojunction solar cells of 1b or 2 with PC71BM were found to have high open-circuit voltages (up to 0.9 V) with power conversion efficiencies of up to 4.5% and 2.6%, respectively. [ABSTRACT FROM AUTHOR]

We present ITO-free rigid and flexible monolithic organic solar cells with an active area of 25 cm 2 . The devices employ a transparent insulator/metal/insulator anode consisting of a molybdenum oxide/silver/zinc sulfide stack that had a peak transmittance of 80% and a sheet resistance of 3.6 Ω/□. Neutron reflectometry showed that zinc sulfide formed a more stable capping layer at the air interface than molybdenum oxide. It was found that blade coating could be used to form good quality large area films on both rigid (glass) and flexible [poly(ethylene terephthalate)] substrates with much reduced material consumption. Cells with an active layer comprised of a blend of poly[ N -9″-heptadecanyl-2,7-carbazole- alt -5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 70 BM) gave a power conversion efficiency of 2.7%, which was 40% higher than a standard ITO-based device. No loss in efficiency was observed when a flexible substrate was used. [ABSTRACT FROM AUTHOR]

Skin-conformable photoplethysmogram (PPG) sensors enable continuous and accurate monitoring of physiological states to efficiently prevent cardiovascular-related diseases. Herein, novel PPG sensors consisting of polymer/oxide hybrid phototransistors, mini-light-emitting diodes, and a framework conformable to epidermis are developed. The key element, a heterojunction phototransistor for efficient energy usage, is composed of an indium gallium zinc oxide (IGZO)-based active layer for low-power consumption and a specific diketopyrrolopyrrole (DPP) polymer layer affording high near-infrared (NIR) light absorbability and hydrophobicity. Therefore, the phototransistors with NIR detectivity of 1.00 × 1013 Jones, rapid photoresponse within the human heart rate range, high reliability against perspiration and mechanical stress, and low operating voltages (< 5 V) are achieved. Using the developed PPG sensors, the heart rate and oxygen saturation of human subjects are successfully detected, which is comparable to the commercial PPG sensors. Furthermore, controlling potential barrier energy at the interface between heterojunction layers, PPG sensors that operate separately at low and high heart rates are implemented for continuous monitoring. Consequently, a distinguished configuration of skin-conformable PPG sensors and a novel concept of an always-on cardiovascular monitoring system while consuming less power are suggested. The study contributes to the development of PPG sensors and may become a potential solution for Healthcare 4.0 applications. [Display omitted] • Photoplethysmogram sensors monitor cardiovascular status to prevent an acute disease. • Limitations of existing sensors are discontinuity and high-power consumption. • Skin-conformable sensors are appropriate to continuous monitoring. • Oxide semiconductors and the novel operation system enable efficient energy usage. • Always-on monitoring system contributes to the development of Healthcare 4.0. [ABSTRACT FROM AUTHOR]

The nanoscale morphology of bulk heterojunctions is highly important for the charge dissociation and transport in organic solar cells and ultimately defines the performance of the cell. The visualization of this nano-morphology in terms of domain size and polymer orientation in a fast and straightforward way is therefore of great interest to evaluate the suitability of a film for efficient solar cells. Here, we demonstrate that the morphology of different blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) can be imaged and analyzed by employing photoemission electron microscopy. • Table-top laser PEEM based measurements of the polymer chain orientation and dichroism are demonstrated for P3HT:PCBM films. • Chain orientation and dichroism are evaluated as discriminators for different film compositions. • Contrast limitations are discussed and possible enhancements are proposed. [ABSTRACT FROM AUTHOR]