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• A ligand-exchange reaction using TOAB was present for stable CsPbI 3−x Br x quantum dots. • TOAB-passivated QDs showed environmental resistance, such as, moisture, light, and heat. • TOAB-passivated devices exhibited a maximum luminescence of 1345 cd/m2 and a maximum external quantum efficiency of 11.7%. In this study, we demonstrate a ligand-exchange reaction using tetraoctylammonium bromide (TOAB) salts for the as-synthesized CsPbI 3 perovskite nanoparticles (NPs) to ensure NPs with stable and improved device performance. TOAB passivation provides a negatively polarized halide-rich surface, higher steric hindrance, and a small amount of Br− anions in the NP lattice to significantly improve the NP stability. The red NP-based light-emitting diodes (NpLEDs) based on TOAB-passivated NPs also exhibited excellent performance because of shorter ligands and stable NPs, with a maximum luminescence of 1345 cd/m2 and a maximum external quantum efficiency of 11.7%. [ABSTRACT FROM AUTHOR]

Abstract: The advantages of using an anode buffer layer of ZnO on the electro–optical properties of organic light emitting devices (OLEDs) are reported. ZnO powders were thermal-evaporated and then treated with ultra-violet (UV) ozone exposure to make the ZnO layers. The turn-on voltage of OLEDs decreased from 4V (4.2cd/m2) to 3V (3.4cd/m2) and the power efficiency increased from 2.7lm/W to 4.7lm/W when a 1-nm-thick ZnO layer was inserted between indium tin oxide (ITO) anodes and α-naphthylphenylbiphenyl diamine (NPB) hole-transporting layers. X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS) results revealed the formation of the ZnO layer and showed that the work function increased by 0.59eV when the ZnO/ITO layer was treated by UV-ozone for 20min. The surface of the ZnO/ITO film became smoother than that of bare ITO film after the UV-ozone treatment. Thus, the hole-injection energy barrier was lowered by inserting an ZnO buffer layer, resulting in a decrease of the turn-on voltage and an increase of the power efficiency of OLEDs. [Copyright &y& Elsevier]

CH 3 NH 3 PbI 3 (MAPbI 3) perovskite thin films were fabricated by using the one-step spin-coating method with a washing-enhanced nucleation (WEN) process under various dropping times, and the resultant thin films were characterized through the reflected-type optical microscope, atomic force microscope, transmittance spectrometer, X-ray diffractometer, photoluminescence spectrometer and water droplet contact-angle imaging system. The experimental results show that the dropping time for the WEN process strongly influences the surface morphology, surface wettability, crystallinity and refractive index of the resultant MAPbI 3 thin films, which dominates the contact at the hydrophilic MAPbI 3 /hydrophobic 6,6-phenyl C 61 butyric acid methyl ester (PCBM) interface and thereby determines the photovoltaic performance. In addition, this investigation helps further understand the effects of the WEN process on the formation of a closely-packed MAPbI 3 thin film. Image 1 • The dropping time for the WEN process highly influences the formation of perovskite films. • The dropping time largely changes the optical and structural properties of perovskite films. • The dropping time can change the surface wettability of perovskite films. • The dropping time dominates the photovoltaic performance of perovskite solar cells. [ABSTRACT FROM AUTHOR]