We report experimental and theoretical investigations with an in-house fabricated Tris(8‐hydroxyquinoline)‐aluminum (Alq3)-based high-speed μ-OLEDs and demonstrate very promising optical pulse responses as short as 400 ps. With a model for an electrically pumped OLED, we simulate the emission of sub-nanosecond optical pulses. The model includes field-dependent (Poole-Frenkel) Langevin recombination and reabsorption of photons by singlets (Stokes-shifted), and by triplets (TA). The good agreement between the measurement and the simulation is the basis for further study of the prospects on the ps time scale, i.e., stimulated emission and conditions for laser operation. For an Alq3-based micro-OLED with high-Q optical cavity, we predict pulsed laser operation with damped relaxation oscillations in the GHz regime and several orders of magnitude linewidth narrowing, but only during 3 ns at most. The simulated current density threshold values vary from 10 kA/cm2 for Q = 500 to less than 1 kA/cm2 for Q = 1000. No CW lasing is found due to the accumulation of triplet excitons for t > 5 ns, which has two deteriorating effects, (1) suppression of the gain-providing singlet excitons due to singlet-triplet absorption (STA) and (2) suppression of the photon density due to photon absorption by triplets (TA). Prospects for CW-lasing with other organic molecules are discussed.

No abstract

We study theoretically the enhancement of the light extraction from an OLED (Organic Light-Emitting Diode) with nanoair-bubbles embedded inside a glass substrate. Due to such a nanostructure inside the substrate, the critical angle which limits the light extraction outside the substrate from the OLED is increased. The theoretical results show that the nanoair bubbles near by the substrate surface can improve the efficiency of the light extraction by 7%. Such a substrate may also be suitable for photovoltaic cells or display screens.

In this work, the one-pot process was employed to synthesize polyaniline/cadmium sulfide hybrid nanocomposite. Herein, for the first time, we report a comprehensive study from the synthesis of the raw materials to the photovoltaic cell performance investigation including the synthesis of the polyaniline/cadmium sulfide hybrid nanocomposite through a one-pot process, a morphology study, the fabrication of a hybrid organic/inorganic solar cell, and the evaluation of the cell performance. To this end, the CdS-to-PANI weight ratio was considered as a key parameter, and 0, 2.5, 5, 10, 15, 20, and 40% were used as the CdS values. FTIR, XRD, and FESEM analyses confirmed that the presence of CdS in the PANI nanotubular network affected the morphology of the hybrid nanocomposite, and changing the CdS-to-PANI ratio tuned the nanotubular network morphology from coarse to fine. UV–visible absorption spectrum studies validated the reduction of PANI bandgap due to the presence of CdS. Likewise, the conductivity of the nanocomposites was also improved compared to neat PANI due to the increasing of charge density. These controlled-morphology nanocomposites were used for organic/inorganic hybrid solar cells based on the configuration of the FTO/ZnO/CdS@PANI/Ag device, and the morphology effects on their performance were investigated. When CdS was incorporated in the PANI nanotubular network, J SC and efficiency increased by, respectively, 4.471 mA·cm–1 and 1.87%. This means a 22-fold increase in J SC and a 1700-fold increase in the solar cell based on 20%CdS@PANI compared to those in the solar cell made with pure PANI. In short, by using the one-pot process, it is possible to hierarchically ensure better control of the morphology of organic and inorganic components, increasing the light absorption edge, reducing the bandgap, and improving the photovoltaic performance of CdS@PANI organic–inorganic hybrid nanocomposites.