Inorganic perovskites for optoelectronic devices
We are involved in advanced research in perovskites (ABX3). We specially focus on synthesis of comparatively stable perovskites in high yield for large area photonic applications. All inorganic perovskites (CsPbX3: X = Cl, Br, and I) are very promising for the development of next-generation optoelectronic and photovoltaic (PV) devices. Inorganic perovskites are important due to its high diffusion length, high absorption coefficient, excellent charge transport properties, and high photostability. In these perovskites, cation or anion substitution can change the optical absorption edge, with or without a change in structure. The realization of highly stable halide perovskites in humid and hot weather like in India is difficult. So our study also focuses on stable phases of perovskites. Besides the photodetectors and LEDs, perovskites possess a great potential for PV applications requiring them to be synthesized using a low cost colloidal synthesis process.
Atomic-Scale Imaging and Nano-Scale Mapping of Perovskite Nanocrystals
Atomic scale transmission electron microscopic images have been utilized to probe the precise arrangement of Cs, Pb, and I atoms in a unit cell of α-CsPbI3 NCs, which is well supported by the VESTA structure. Theoretical calculation using density functional theory of our experimental structure reveals the realization of direct band to band transition with a lower band gap, a higher absorption coefficient, and stronger covalent bonding between the Pb and I atoms in the [PbI6]4– octahedral, as compared to reported standard structure. Nanoscale surface mapping using Kelvin probe force microscopy yielding contact potential difference (CPD) and conductive atomic force microscopy for current mapping have been employed on α-CsPbI3 NCs films deposited on different DMSO doped PEDOT:PSS layers.
-Mahato, S et al. “Atomic-Scale Imaging and Nano-Scale Mapping of Cubic α-CsPbI3 Perovskite Nanocrystals for Inverted Perovskite Solar Cells” in ACSami (2022). DOI: 10.1021/acsami.1c20794
Inorganic mixed halide perovskites for wavelength tunable LED
Utilizing the superior luminescence properties and high color purity of inorganic perovskite nanocrystals (NCs), we report the fabrication of color-saturated CsPbBr3−xIx (x = 0–3)/ZnO heterojunctions based white light emitting diodes (LEDs) on a flexible platform. Here, bandgap engineered mixed halide perovskite NCs have been prepared by solution phase synthesis technique that was spin coated on sputtered ZnO film, acting as an electron injector layer as well as an efficient luminescent material.
-Pal, S et al. “Strain mediated light emission using heterojunctions of all-inorganic mixed-halide perovskite nanocrystals via piezo-phototronic effect” in Nano Energy (2021). DOI: 10.1016/j.nanoen.2021.106200
Single-crystalline β-CsPbI3 nanorods for photovoltaic devices
Colloidal synthesis of all inorganic single-crystalline β-CsPbI3 nanorods with an excellent photostability under 45–55% humidity displays the superior characteristics of fabricated inverted perovskite solar cells without any device passivation. Atomic resolution transmission electron micrography reveals the probable distribution of Cs, Pb, and I atoms in a single β-phase CsPbI3 nanorod.
-Mahato, S et al. “Highly Air-Stable Single-Crystalline β-CsPbI3 Nanorods: A Platform for Inverted Perovskite Solar Cells” in Adv. Energy. Mat. (2020). DOI: 10.1002/aenm.202001305
Tunable properties of lead halide perovskites
Environmentally stable lead halide perovskite nanostructures with engineered composition and morphology are attractive because of their exotic optical properties. Here, we report the synthesis of monodispersed (∼20 nm) CsPbI3 cubic perovskite nanocrystals (NCs) using edible olive oil as a solvent as well as a chelating reagent. The anion exchange temperature has a distinct effect on the morphology of the CsPbBr3 nanostructure and the anion exchange reaction rate.
-Ghorai, A et al. “Surfactant-Induced Anion Exchange and Morphological Evolution for Composition-Controlled Caesium Lead Halide Perovskites with Tunable Optical Properties” in ACSomega (2019). DOI: 10.1021/acsomega.9b00829
