Microwave-Assisted Non-aqueous and Low-Temperature Synthesis of Titania and Niobium-Doped Titania Nanocrystals and Their Application in Halide Perovskite Solar Cells as Electron Transport Layers.

Undoped and Nb-doped TiO2 nanocrystals are prepared by a microwave-assisted non-aqueous sol-gel method based on a slow alkyl chloride elimination reaction between metal chlorides and benzyl alcohol. Sub-4 nm nanoparticles are grown under microwave irradiation at 80 °C in only 3 h with precise control of growth parameters and yield. The obtained nanocrystals could be conveniently used to cast compact TiO2 or Nb-doped TiO2 electron transport layers for application in formamidinium lead iodide-based photovoltaic devices. Niobium doping is found to improve the cell performance by increasing the conductivity and mobility of the electron transport layer. At the same time, a measurable decrease in parasitic light absorption in the low wavelength portion of the spectrum was observed.

Direct X-ray and electron-beam lithography of halogenated zeolitic imidazolate frameworks.

Metal-organic frameworks (MOFs) offer disruptive potential in micro- and optoelectronics because of the unique properties of these microporous materials. Nanoscale patterning is a fundamental step in the implementation of MOFs in miniaturized solid-state devices. Conventional MOF patterning methods suffer from low resolution and poorly defined pattern edges. Here, we demonstrate the resist-free, direct X-ray and electron-beam lithography of MOFs. This process avoids etching damage and contamination and leaves the porosity and crystallinity of the patterned MOFs intact. The resulting high-quality patterns have excellent sub-50-nm resolution, and approach the mesopore regime. The compatibility of X-ray and electron-beam lithography with existing micro- and nanofabrication processes will facilitate the integration of MOFs in miniaturized devices.