Abhijit Hazarika

Bio: Abhijit Hazarika is an academic researcher from National Renewable Energy Laboratory. The author has contributed to research in topics: Perovskite (structure) & Quantum dot. The author has an hindex of 17, co-authored 35 publications receiving 1381 citations. Previous affiliations of Abhijit Hazarika include S.N. Bose National Centre for Basic Sciences & University of Chicago.

Near-room-temperature colossal magnetodielectricity and multiglass properties in partially disordered La2NiMnO6

Abstract: We report magnetic, dielectric, and magnetodielectric responses of the pure monoclinic bulk phase of partially disordered La2NiMnO6, exhibiting a spectrum of unusual properties and establish that this compound is an intrinsically multiglass system with a large magnetodielectric coupling (8%-20%) over a wide range of temperatures (150-300 K). Specifically, our results establish a unique way to obtain colossal magnetodielectricity, independent of any striction effects, by engineering the asymmetric hopping contribution to the dielectric constant via the tuning of the relative-spin orientations between neighboring magnetic ions in a transition-metal oxide system. We discuss the role of antisite (Ni-Mn) disorder in emergence of these unusual properties.

High efficiency perovskite quantum dot solar cells with charge separating heterostructure.

Abstract: Metal halide perovskite semiconductors possess outstanding characteristics for optoelectronic applications including but not limited to photovoltaics. Low-dimensional and nanostructured motifs impart added functionality which can be exploited further. Moreover, wider cation composition tunability and tunable surface ligand properties of colloidal quantum dot (QD) perovskites now enable unprecedented device architectures which differ from thin-film perovskites fabricated from solvated molecular precursors. Here, using layer-by-layer deposition of perovskite QDs, we demonstrate solar cells with abrupt compositional changes throughout the perovskite film. We utilize this ability to abruptly control composition to create an internal heterojunction that facilitates charge separation at the internal interface leading to improved photocarrier harvesting. We show how the photovoltaic performance depends upon the heterojunction position, as well as the composition of each component, and we describe an architecture that greatly improves the performance of perovskite QD photovoltaics.

Size-Dependent Lattice Structure and Confinement Properties in CsPbI3 Perovskite Nanocrystals: Negative Surface Energy for Stabilization

Abstract: CsPbI3 nanocrystals with narrow size distributions were prepared to study the size-dependent properties. The nanocrystals adopt the perovskite (over the nonperovskite orthorhombic) structure with i...

Perovskite Quantum Dot Photovoltaic Materials beyond the Reach of Thin Films: Full-Range Tuning of A-Site Cation Composition.

Abstract: We present a cation-exchange approach for tunable A-site alloys of cesium (Cs+) and formamidinium (FA+) lead triiodide perovskite nanocrystals that enables the formation of compositions spanning the complete range of Cs1–xFAxPbI3, unlike thin-film alloys or the direct synthesis of alloyed perovskite nanocrystals. These materials show bright and finely tunable emission in the red and near-infrared range between 650 and 800 nm. The activation energy for the miscibility between Cs+ and FA+ is measured (∼0.65 eV) and is shown to be higher than reported for X-site exchange in lead halide perovskites. We use these alloyed colloidal perovskite quantum dots to fabricate photovoltaic devices. In addition to the expanded compositional range for Cs1–xFAxPbI3 materials, the quantum dot solar cells exhibit high open-circuit voltage (VOC) with a lower loss than the thin-film perovskite devices of similar compositions.

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects

Abstract: The photovoltaics of organic–inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regardi...

Colloidal Quantum Dot Solar Cells.

Abstract: Graham H. Carey,† Ahmed L. Abdelhady,‡ Zhijun Ning, Susanna M. Thon, Osman M. Bakr,‡ and Edward H. Sargent*,† †Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada ‡Division of Physical Sciences and Engineering, Solar & Photovoltaics Engineering Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia School of Physical Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai 201210, China Department of Electrical and Computer Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States

Colloidal CsPbBr3 Perovskite Nanocrystals: Luminescence beyond Traditional Quantum Dots.

Abstract: Traditional CdSe-based colloidal quantum dots (cQDs) have interesting photoluminescence (PL) properties. Herein we highlight the advantages in both ensemble and single-nanocrystal PL of colloidal CsPbBr3 nanocrystals (NCs) over the traditional cQDs. An ensemble of colloidal CsPbBr3 NCs (11 nm) exhibits ca. 90 % PL quantum yield with narrow (FWHM=86 meV) spectral width. Interestingly, the spectral width of a single-NC and an ensemble are almost identical, ruling out the problem of size-distribution in PL broadening. Eliminating this problem leads to a negligible influence of self-absorption and Forster resonance energy transfer, along with batch-to-batch reproducibility of NCs exhibiting PL peaks within ±1 nm. Also, PL peak positions do not alter with measurement temperature in the range of 25 to 100 °C. Importantly, CsPbBr3 NCs exhibit suppressed PL blinking with ca. 90 % of the individual NCs remain mostly emissive (on-time >85 %), without much influence of excitation power.

Mn-Doped Quantum Dot Sensitized Solar Cells: A Strategy to Boost Efficiency over 5%

Abstract: To make Quantum Dot Sensitized Solar Cells (QDSC) competitive, it is necessary to achieve power conversion efficiencies comparable to other emerging solar cell technologies. By employing Mn2+ doping of CdS, we have now succeeded in significantly improving QDSC performance. QDSC constructed with Mn-doped-CdS/CdSe deposited on mesoscopic TiO2 film as photoanode, Cu2S/Graphene Oxide composite electrode, and sulfide/polysulfide electrolyte deliver power conversion efficiency of 5.4%.

Quantum Dot Solar Cells. The Next Big Thing in Photovoltaics.

Abstract: The recent surge in the utilization of semiconductor nanostructures for solar energy conversion has led to the development of high-efficiency solar cells. Some of these recent advances are in the areas of synthesis of new semiconductor materials and the ability to tune the electronic properties through size, shape, and composition and to assemble quantum dots as hybrid assemblies. In addition, processes such as hot electron injection, multiple exciton generation (MEG), plasmonic effects, and energy-transfer-coupled electron transfer are gaining momentum to overcome the efficiency limitations of energy capture and conversion. The recent advances as well as future prospects of quantum dot solar cells discussed in this perspective provide the basis for consideration as “The Next Big Thing” in photovoltaics.