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We demonstrate efficient and air-stable small-molecule bulk heterojunction (SM BHJ) solar cells by introducing titanium suboxide (TiOx) between the active layer and the cathode as an electric adhesive layer. The SM BHJ solar cell with the TiOx interlayer exhibits improved power conversion efficiency of 6.4% as well as greatly enhanced device lifetime. Analysis of the dark diode characteristics and comparison of the current density-voltage characteristics upon heat annealing indicate that the TiOx interlayer improves the electrical contact between the active layer and the cathode, thereby resulting in efficient sweep-out of photogenerated charge carriers.

We fabricated ZnO-nanowire (NW) field-effect transistors (FETs) coated with poly(3-hexylthiophene) (P3HT) and characterized the electron-transfer characteristics from the P3HT to the ZnO NWs. Under irradiation by laser light with a wavelength of 532 nm, photo-induced electrons were created in the P3HT and then transported to the ZnO NWs, constituting a source-drain current in the initially enhancement-mode P3HT-coated ZnO-NW FETs. As the intensity of the light increased, the current increased, and its threshold voltage shifted to the negative gate-bias direction. We estimated the photo-induced electron density and the electron-transfer characteristics, which will be helpful for understanding organic-inorganic hybrid optoelectronic devices.

This work presents homogeneous bulk heterojunction (BHJ) networks between a push-pull π-conjugated polymer donor, poly(2,7-(5,5,10,10-tetrakis(2-ethylhexyl)-5,10-dihydroindeno[2,1-a]indene)-alt-5,5-(4,7-bis(2,2-bithien-5-yl)-2,2-dimethyl-2H-benzimidazole)) (PININE-BBTMBI) and a fullerene derivative acceptor, [6,6]-phenyl C71-butyric acid methyl ester (PC71BM). By introducing a bi-thiophene unit between the electron-rich and electron-deficient moieties in a repeating unit, the surface energy of PININE-BBTMBI increased to that of PC71BM, enhancing its miscibility in PININE-BBTMBI/PC71BM blends. Direct evidence obtained via atomic force microscopy and the performance of BHJ solar cells indicate that the introduction of the bi-thiophene unit leads to homogeneous BHJ networks and high-performance BHJ solar cells by matching the surface energies at the polymer/fullerene interfaces.

We report a novel approach that leads to a significant improvement in the performance of transparent polymer light-emitting diodes (TPLEDs). By introducing a solution-based titanium oxide (TiOx) layer, we have demonstrated that the device performance of TPLEDs using aluminum-doped zinc oxide (AZO) top electrodes is enhanced. The TiOx layer lowers the energy barrier between the luminescent polymer and the AZO top electrode by modifying the WF of the top AZO electrodes. Moreover, the TiOx layer prevents the damage caused by UV radiation and by highly energetic ions generated during the AZO sputtering.