Roadmap on organic–inorganic hybrid perovskite semiconductors and devices

in APL Materials (2021)

Metal halide perovskites are the first solution processed semiconductors that can compete in their functionality with conventional semiconductors, such as silicon. Over the past several years, perovskite ... [more ▼]

Metal halide perovskites are the first solution processed semiconductors that can compete in their functionality with conventional semiconductors, such as silicon. Over the past several years, perovskite semiconductors have reported breakthroughs in various optoelectronic devices, such as solar cells, photodetectors, light emitting and memory devices, and so on. Until now, perovskite semiconductors face challenges regarding their stability, reproducibility, and toxicity. In this Roadmap, we combine the expertise of chemistry, physics, and device engineering from leading experts in the perovskite research community to focus on the fundamental material properties, the fabrication methods, characterization and photophysical properties, perovskite devices, and current challenges in this field. We develop a comprehensive overview of the current state-of-the-art and offer readers an informed perspective of where this field is heading and what challenges we have to overcome to get to successful commercialization. [less ▲]

The other model antiferroelectric: PbHfO3 thin films from ALD precursors

in APL MATERIALS (2021), 9(2),

Antiferroelectric PbHfO3 is grown from atomic layer deposition precursors lead bis(dimethylaminomethylpropanolate) and tetrakis dimethylamino hafnium with H2O and O-3 oxidizers in thicknesses from 20 nm ... [more ▼]

Antiferroelectric PbHfO3 is grown from atomic layer deposition precursors lead bis(dimethylaminomethylpropanolate) and tetrakis dimethylamino hafnium with H2O and O-3 oxidizers in thicknesses from 20 nm to 200 nm at a substrate temperature of 250 degrees C. X-ray analysis shows an as-grown crystalline PbO phase that diffuses into an amorphous HfO2 matrix upon annealing to form a randomly oriented, orthorhombic PbHfO3 thin film. Electrical characterization reveals characteristic double hysteresis loops with maximum polarizations of around 30 mu C/cm(2) and transition fields of 350 kV/cm-500 kV/cm depending on the thickness. Temperature-dependent permittivity and polarization testing show a phase transition at 185 degrees C, most probably to the paraelectric phase, but give no clear evidence for the intermediate phase known from bulk PbHfO3. The energy storage density for the films reaches 16 J/cm(3) at 2 MV/cm. A dielectric tunability of 221 is available within 1 V for the thinnest film. These results highlight the unique spectrum of properties available for thin film perovskite antiferroelectrics. [less ▲]

Role of the ferroelastic strain in the optical absorption of BiVO4

in APL MATERIALS (2020), 8(8),

Bismuth vanadate (BiVO4) has recently been under focus for its potential use in photocatalysis thanks to its well-suited absorption edge in the visible light range. Here, we characterize the optical ... [more ▼]

Bismuth vanadate (BiVO4) has recently been under focus for its potential use in photocatalysis thanks to its well-suited absorption edge in the visible light range. Here, we characterize the optical absorption of a BiVO4 single crystal as a function of temperature and polarization direction by reflectance and transmittance spectroscopy. The optical bandgap is found to be very sensitive to the temperature, and to the tetragonal-to-monoclinic ferroelastic transition at 523 K. The anisotropy, as measured by the difference in the absorption edge for the light polarized parallel and perpendicular to the principal axis, is reduced from 0.2 eV in the high-temperature tetragonal phase to 0.1 eV at ambient temperature. We show that this evolution is dominantly controlled by the ferroelastic shear strain. These findings provide a route for further optimization of bismuth vanadate-based light absorbers in photocatalytic devices. [less ▲]