The authors report on highly efficient organic light emitting diodes (OLEDs) consisting of only two organic layers. The key to the simplification is the direct injection of holes into the wide band gap hole transport material 4,4′,4″-tris(N-carbazolyl)-triphenyl amine (highest occupied molecular orbital is 5.9eV) through an indium tin oxide/tungsten oxide (WO3) anode. Kelvin probe analysis has revealed an extremely high work function of 6.4eV for WO3. The efficiencies of the simplified OLEDs exceed 40lm∕W and 45cd∕A at a brightness of 100cd∕m2, unsurpassed by other comparably simple OLED devices. Therefore, our OLED architecture demonstrates highly efficient, yet easy to fabricate devices.

We demonstrate an organic thin-film distributed feedback (DFB) laser pumped by an inorganic violet laser diode (λ=406nm). The active organic medium consists of a highly efficient, modified poly(9,9-dioctylfluorene) derivative containing 12% of statistical intrachain 6,6′-(2,2′-octyloxy-1,1′-binaphthalene) binaphthyl spacer groups. The polymer is doped with 4wt% of the stilbene dye 1,4-bis(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinylbenzene). This guest-host system features minimum lasing threshold energy densities below 1μJ∕cm2 for second order DFB resonator geometries and significant absorption (7.3×104cm−1) at the wavelength of the pumping diode laser. The entire setup states an extremely compact and cost effective, laser source tunable between 496 and 516nm.

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We present highly efficient transparent organic light emitting diodes (OLEDs) with Al doped ZnO (AZO) electrodes prepared by atomic layer deposition and pulsed laser deposition (PLD). The power and current efficiencies exceed 27 lm/W and 44 cd/A at a brightness level of 100 cd/m2, respectively. At the same time, the transmissivity of the devices is above 73% in the visible part of the spectrum. Owing to an efficient WO3 buffer layer and an optimized PLD process for the deposition of the top AZO electrode, the OLEDs show leakage current densities as low as 3×10−5 mA/cm2 at a reverse bias of 6 V. Therefore, our study paves the way for indium-free, see-through OLED displays.

Tandem solar cells based on the combination of a poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester and a copper phthalocyanine:fullerene subcell are reported. By using a highly transparent, high-work function WO3 layer as part of the interconnecting system for the two subcells, the authors demonstrate stacked devices with power conversion efficiencies as high as 4.6%. The efficiency of the stacked devices is close to the sum of the efficiencies of the individual subcells.