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Although all-inorganic perovskite light emitting diodes (PeLED) have satisfactory stability under an ambient atmosphere, producing devices with high performance is challenging.

To employ TiO2 as an efficient photocatalyst, high reactivity under visible light and improved separation of photoexcited carriers are required. An effective co-doping approach is applied to modify the photocatalytic properties of TiO2 by doping vanadium (transition metal) and yttrium (rare earth element). V and/or Y codoped TiO2 was prepared using hydrothermal method without any post calcination for crystallization. Based on density functional theory, compensated and noncompensated V, Y codoped TiO2 models were constructed and their structural, electronic, and optical properties were calculated. Through combined experimental characterization and theoretical modeling, V, Y codoped TiO2 exhibited high absorption coefficient with enhanced visible light absorption. All the prepared samples showed pure anatase phase and spherical morphology with uniform particle distribution. Electronic band structure demonstrates that V, Y codoping drastically reduced the band gap of TiO2. It is found that both the doped V and Y exist in the form of substitutional point defects replacing Ti atom in the lattice. The photocatalytic activity, evaluated by the degradation of methyl orange, displays that the codoped TiO2 sample exhibits enhanced visible light photocatalytic activity. The synergistic effects of V and Y drastically improved the Brunauer-Emmett-Teller specific surface area, visible light absorption, and electron-hole pair's separation leading to the enhanced visible light catalytic activity.

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performance such as low operation voltages, good device stability, and high color quality. [1][2][3] However, the deep valence band (VB) level of QDs results in a large band offset for hole injection and limits the electroluminance (EL) efficiency. [4][5][6][7][8] To overcome the hindrance, multi-holetransporting layers (multi-HTLs) have been used to increase the external quantum efficiency (EQE) up to 20.5%, bringing it closer to the theoretical maximum of 21%. [9][10][11][12] Nevertheless, the number of transport layers can limit the device performance in a multi-HTL device because of charge imbalance and accumulation. [11,13,14] In this regard, HTL materials with proper band alignment and precise thickness are required to maximize the hole diffusion in materials. [15] In particular, the unequal energy barriers at both sides of QD layer cause imbalanced charge injection (CI) into the QD layer, leading to charge density accumulation at the interfaces of HTL/QDs and QD/electron transport layer (ETL). [16] The charge imbalance will further lead to luminance quenching via the nonradiative Auger recombination mechanism. [17] Depending on the density of available electrons and holes, the charge accumulation facilitates Förster resonance energy transfer (FRET), which is a dominating undesirable process limiting the QLED efficiency. [18,19] Furthermore, the limited carrier injection normally results in instability and higher operation voltage of Development of quantum dots (QDs) based light-emitting diodes (QLEDs) is driven by attractive properties of these fluorophores such as precise Gaussian distribution, tunable emission, and facile solution processability. The performance of QLED devices is limited by intrinsic factors such as luminance quenching in quantum dots due to imbalanced carrier injection predominantly caused by a large hole injection barrier as well as by extrinsic processes such as nonradiative recombination at active layer interfaces.The Auger recombination problem is overcome by charge siphoning at the interfaces between QDs and charge-transporting material. A simplest trilayer (p-i-n) LED structure is fabricated using an all-solution processing method: a carefully engineered p-type polymeric hole transport layer with a gradient work function is incorporated. The gradient work function creates the cascading energy levels from the moderate Fermi level anode to the deeplying valence band level of QDs. As a result, the QLEDs exhibit significantly improved external quantum efficiencies and luminous efficiencies of 15.9% and 31.8 cd A −1 , 17.4% and 59.3 cd A −1 , and 12.8% and 14.4 cd A −1 for red, green, and blue light-emitting devices, respectively. It is expected that the concept demonstrated here will facilitate the design and development of efficient solution-processible QLEDs for full-color displays.

Photoanode materials with optimized particle sizes, excellent surface area and dye loading capability are preferred in good-performance dye sensitized solar cells. Herein, we report on an efficient dye-sensitized mesoporous photoanode of Ti doped zinc oxide (Ti-ZnO) through a facile hydrothermal method. The crystallinity, morphology, surface area, optical and electrochemical properties of the Ti-ZnO were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction. It was observed that Ti-ZnO nanoparticles with a high surface area of 131.85 m2 g−1 and a controlled band gap, exhibited considerably increased light harvesting efficiency, dye loading capability, and achieved comparable solar cell performance at a typical nanocrystalline ZnO photoanode.

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