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We report a fabrication method of controlling the doped concentration of phosphorescent dye to induce the trap-site in an emitting layer (EML) for an efficient near-infrared (NIR) organic upconversion device (OUD). Such an OUD was used as a device configuration of ITO/mixed layer of chloroaluminum phthalocyanine and C60/1,1-bis(di-4-tolylaminophenyl) cyclohexane/4,4′ -Bis(N-carbazolyl)-1,1′ -biphenyl doped with fac-tris (2-phenylpyridine) iridium (III) [Ir(ppy)3]/4,7-diphenyl-l,10-phenanthroline/CS2CO3/Ag to provide a green emission under NIR illumination. Our optimized OUD with a high Ir(ppy)3 doped concentration of ∼13 wt% exhibited a higher electroluminescent efficiency in the display unit and was suitable for inducing a large amount of trap-sites in the EML, which effectively blocked the hole and electron carrier in the EML. To induce the trap-site in the EML by the doping process, we used a hole- and electron-only device to examine the OUD with a lower dark current density. As a result, an optimal OUD with a current gain as high as 21,300 (defined as the light current density divided by dark current density) at a driving voltage of 3 V was successfully achieved.

We report here synthesis and photovoltaic properties of three merocyanines dyes (DPPT, DTPT, 1-NPPT) which are functionalized with electron withdrawing thiazolidenemalononitrile and electron rich diarylamine functionalities. It is found that structural feature of the diarylamino groups has a profound effect on the physical properties such as the absorption spectrum, oxidation potential, and HOMO/LUMO energy levels. The compound DTPT containing a better electron-donating ditolyl group, exhibits red-shifted absorption with relatively higher molar extinction coefficient, indicating its better light-harvesting ability. Hole mobility of these compounds is found to be strongly dependent on the various intermolecular interactions. Interestingly, single crystal structures reveal that the crystal packing motifs are rather closely related to the observed hole mobility in a trend of DPPT > DTPT > 1-NPPT. Vacuum-processed small-molecule organic solar cells were fabricated using the title merocyanines as p-type materials (donor) in combination with fullerene (C60 or C70) as n-type material (acceptor) with various device configurations. Among them, the DPPT-based devices outperform the devices based on DTPT and 1-NPPT. The power conversion efficiency (PCE) of DPPT-based device was improved from 1.55% of a BHJ device to 2.63% of a PMHJ device and 3.52% of a PMHJ device without the thin donor layer.

A topological insulating Bi2Te3 single crystal was successfully grown with good uniformity using a home-made resistance-heated floated zone furnace. The temperature-dependent resistance and Hall voltage confirm that the transport is metallic and the overall carriersareholes. The angle and temperature dependence of the quantum Shubnikov–de Haas oscillation period amplitude suggests that the transport comes from the carriers of surface states. The Berry phase, determined from Landau level diagram, also reveals that the transport carriers are Dirac fermions. In contrast with many previous publications, the transport parameters relating to the surface carriers derived from the relationship of the Lifshitz–Kosevich (LK) theory are consistent with angle resolved photoemission spectroscopy results.