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In this work, a flexible perovskite photodetector is demonstrated with a transferable TiO2 nanorod (NR) as an electron transport layer (ETL). The TiO2 NRs are grown by the hydrothermal method on Ni metal buffer layer/Si (100) substrates. During the growth process of TiO2 NRs in solution, the Ni sacrificial buffer layer is removed by hydrochloric acid in the initial stage. The resulting suspended seed layer can then sustain the growth of TiO2 NRs in both the top and bottom directions. The successfully grown TiO2 NRs are now transferred onto an ITO‐coated PET substrate as an ETL for the flexible Cs2AgBiBr6 perovskite photodetectors. The fabricated photodetector operates under a wavelength of 405 nm, and at an external bias voltage of −0.3 V, it exhibits an outstanding performance with an on/off ratio of 1.23 × 104, photoresponsivity (R) of 0.666 A W−1, and a detectivity (D*) of 9.29 × 1012 Jones. In terms of flexibility, the optoelectronic performance of each device is well kept within 5% after 300 bending test cycles with a radius of 1 cm. The suggested transferable TiO2 NRs can improve the efficiency of flexible optoelectronic devices that require synergistic electron transfer effects by using heterostructures with TiO2 nanostructures. [ABSTRACT FROM AUTHOR]

We report on the fabrication of TiO2 nanosphere (NS) monolayer arrays for the enhancement of light extraction quantum efficiency of GaN-based light-emitting diodes (LEDs). The fabricated TiO2 NSs monolayer arrays were composed of different phases of anatase (An-) and amorphous (Am-) TiO2. The arrays were transferred onto the topmost layer of LED chips via the facile icing transfer method. The LED chips covered with Am-TiO2 NS monolayer arrays showed 3.0- times enhanced light output power intensity compared with reference LED chips at a fixed injection current of 100 mA. The enhanced light extraction of LED chips by an Am-TiO2 NS monolayer can be attributed to a high transmittance (91.1%) in visible and increased light extraction probability of photons generated in LEDs, resulting from the enhanced light coupling efficiency by reduced total internal reflection (TIR). Finite-difference time-domain (FDTD) simulation results also agreed well with the experimentally observed results. Based on the experimental and theoretical results, our suggested Am- and An-TiO2 NS arrays can be considered a very facile and effective method to improve the device performance of various visible LED chips. [ABSTRACT FROM AUTHOR]

A thermal interface material (TIM) is a substance that reduces the thermal resistance between a heat source and heat sink, which facilitates heat conduction towards the outside. In this study, a TiO2 nanosphere (NS)-filler based TIM was fabricated via facile processes such as spin-coating and icing methods. Thermal conductivity of the fabricated TiO2 NS-based TIM was enhanced by increasing the loading contents of the TiO2 NS-filler and successfully cooling down the GPU chipset temperature from 62 °C to 50 °C. Moreover, the TIM with the TiO2 NS-monolayer additionally lowered the GPU temperature by 1–7 °C. The COMSOL simulation results show that the TiO2 NS-monolayer, which was in contact with the heat source, boosts the heat transfer characteristics from the heat source toward the inside of the TIM. The suggested metal oxide monolayer-based TIM is an effective structure that reduces the temperature of the device without an additional filler loading, and it is expected to have a wide range of applications for the thermal management of advanced devices. [ABSTRACT FROM AUTHOR]

Given a factor code ${\it\pi}$ from a shift of finite type $X$ onto a sofic shift $Y$, the class degree of ${\it\pi}$ is defined to be the minimal number of transition classes over the points of $Y$. In this paper, we investigate the structure of transition classes and present several dynamical properties analogous to the properties of fibers of finite-to-one factor codes. As a corollary, we show that for an irreducible factor triple, there cannot be a transition between two distinct transition classes over a right transitive point, answering a question raised by Quas. [ABSTRACT FROM PUBLISHER]