Tarak Nath Mandal

Bio: Tarak Nath Mandal is an academic researcher from University of Calcutta. The author has contributed to research in topics: Schiff base & Pyrazole. The author has an hindex of 19, co-authored 36 publications receiving 6624 citations. Previous affiliations of Tarak Nath Mandal include Indian Institute of Science.

Chemical Management for Colorful, Efficient, and Stable Inorganic–Organic Hybrid Nanostructured Solar Cells

Abstract: Chemically tuned inorganic–organic hybrid materials, based on CH3NH3(═MA)Pb(I1–xBrx)3 perovskites, have been studied using UV–vis absorption and X-ray diffraction patterns and applied to nanostructured solar cells. The band gap engineering brought about by the chemical management of MAPb(I1–xBrx)3 perovskites can be controllably tuned to cover almost the entire visible spectrum, enabling the realization of colorful solar cells. We demonstrate highly efficient solar cells exhibiting 12.3% in a power conversion efficiency of under standard AM 1.5, for the most efficient device, as a result of tunable composition for the light harvester in conjunction with a mesoporous TiO2 film and a hole conducting polymer. We believe that the works highlighted in this paper represent one step toward the realization of low-cost, high-efficiency, and long-term stability with colorful solar cells.

Efficient inorganic–organic hybrid heterojunction solar cells containing perovskite compound and polymeric hole conductors

Abstract: Inorganic‐organic hybrid structures have become innovative alternatives for next-generation dye-sensitized solar cells, because they combine the advantages of both systems. Here, we introduce a layered sandwich-type architecture, the core of which comprises a bicontinuous three-dimensional nanocomposite of mesoporous (mp)-TiO2 ,w ith CH 3NH3PbI3 perovskite as light harvester, as well as a polymeric hole conductor. This platform creates new opportunities for the development of low-cost, solution-processed, high-efficiency solar cells. The use of a polymeric hole conductor, especially poly-triarylamine, substantially improves the open-circuit voltage V oc and fill factor of the cells. Solar cells based on these inorganic‐organic hybrids exhibit a short-circuit current density Jsc of 16.5 mA cm 22 , Voc of 0.997 V and fill factor of 0.727, yielding a power conversion efficiency of 12.0% under standard AM 1.5 conditions.

Sb2Se3‐Sensitized Inorganic–Organic Heterojunction Solar Cells Fabricated Using a Single‐Source Precursor

Abstract: The photovoltaic performance of Sb2Se3-sensitized heterojunction solar cells, which were fabricated by a simple deposition of Sb2Se3 on mesoporous TiO2 by an approach that features multiple cycles of spin coating with a single-source precursor solution and thermal decomposition, is reported. Poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothioadiazole)] was used as the hole-transporting material. The most efficient cell exhibited a short-circuit current density of 22.3 mA cm−2, an open-circuit voltage of 304.5 mV, and a fill factor of 47.2 %, yielding a power conversion efficiency of 3.21 % under standard test conditions (irradiation of 1000 W m−2, air mass=1.5 G). The results of this study imply that the developed approach has a high potential as a simple and effective route for the fabrication of efficient and inexpensive solar cells.

Efficient Inorganic‐Organic Heterojunction Solar Cells Employing Sb2(Sx/Se1‐x)3 Graded‐Composition Sensitizers

Abstract: Dr. Y. C. Choi, Dr. Y. H. Lee, Dr. J. H. Noh, Dr. T. N. Mandal, W. S. Yang, Dr. S. I. Seok Division of Advanced Materials Korea Research Institute of Chemical Technology 141 Gajeong-Ro, Yuseong-Gu, Daejeon , 305.600 , Republic of Korea Prof. S. H. Im Department of Chemical Engineering Kyung Hee University oungin-si , Y 446–701 , Republic of Korea Prof. S. I. Seok Department of Energy Science Sungkyunkwan University Suwon , 440–746 , Republic of Korea E-mail: seoksi@skku.edu

Ultrastable Luminescent Hybrid Bromide Perovskite@MOF Nanocomposites for the Degradation of Organic Pollutants in Water

Abstract: Hybrid bromide perovskites (HBPs) have emerged as a promising candidate in optoelectronic applications, although instability of the materials under working conditions has retarded the progress toward commercialization. As a rational approach to address this core issue, we herein report the synthesis of a series of ultrastable composite materials, wherein HBP nanocrystals (NCs) have been stabilized within a well-known chemically stable metal–organic framework (MOF) viz. zeolitic imidazolate framework (ZIF-8) via a pore-encapsulated solvent-directed (PSD) approach. The composites maintain their structural integrity as well as photoluminescence (PL) properties upon dipping into a wide range of polar solvents including water (even in boiling conditions), prolonged exposure to UV irradiation, and elevated temperature for longer periods of time. Further, on the basis of high stability, HBP@MOF composites have been demonstrated as heterogeneous photocatalysts to degrade toxic organic pollutants directly in water.

Sequential deposition as a route to high-performance perovskite-sensitized solar cells

Abstract: Following pioneering work, solution-processable organic-inorganic hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixture of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled precipitation of the perovskite produces large morphological variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from solution into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a solution of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphology than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approximately 15 per cent (measured under standard AM1.5G test conditions on solar zenith angle, solar light intensity and cell temperature). This two-step method should provide new opportunities for the fabrication of solution-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices.

Electron-hole diffusion lengths exceeding 1 micrometer in an organometal trihalide perovskite absorber.

Abstract: Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI(3-x)Cl(x)) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.

Efficient planar heterojunction perovskite solar cells by vapour deposition

Abstract: Many different photovoltaic technologies are being developed for large-scale solar energy conversion. The wafer-based first-generation photovoltaic devices have been followed by thin-film solid semiconductor absorber layers sandwiched between two charge-selective contacts and nanostructured (or mesostructured) solar cells that rely on a distributed heterojunction to generate charge and to transport positive and negative charges in spatially separated phases. Although many materials have been used in nanostructured devices, the goal of attaining high-efficiency thin-film solar cells in such a way has yet to be achieved. Organometal halide perovskites have recently emerged as a promising material for high-efficiency nanostructured devices. Here we show that nanostructuring is not necessary to achieve high efficiencies with this material: a simple planar heterojunction solar cell incorporating vapour-deposited perovskite as the absorbing layer can have solar-to-electrical power conversion efficiencies of over 15 per cent (as measured under simulated full sunlight). This demonstrates that perovskite absorbers can function at the highest efficiencies in simplified device architectures, without the need for complex nanostructures.

Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber

Abstract: Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI(3-x)Cl(x)) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.

Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH3NH3PbI3

Abstract: Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors.