Biplab Ghosh

Bio: Biplab Ghosh is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Perovskite (structure) & Materials science. The author has an hindex of 9, co-authored 17 publications receiving 863 citations. Previous affiliations of Biplab Ghosh include Academy of Scientific and Innovative Research & Council of Scientific and Industrial Research.

Rb as an Alternative Cation for Templating Inorganic Lead-Free Perovskites for Solution Processed Photovoltaics

Abstract: Even though perovskite solar cells have reached 22% efficiency within a very short span, the presence of lead is a major bottleneck to its commercial application. Tin and germanium based perovskites failed to be viable replacements due to the instability of their +2 oxidation states. Antimony could be a possible replacement, forming perovskites with structure A3M2X9. However, solution processing of Cs, organic ammonium based Sb perovskites result in the formation of the dimer phase with poor charge transport properties. Here we demonstrate that Rb can template the formation of the desired layered phase irrespective of processing methodologies, enabling the demonstration of efficient lead-free perovskite solar cells.

Limitations of Cs3Bi2I9 as Lead-Free Photovoltaic Absorber Materials.

Abstract: Lead (Pb) halide perovskites have attracted tremendous attention in recent years because of their rich optoelectronic properties, which have resulted in more than 22% power conversion efficient photovoltaics (PVs). Nevertheless, Pb-metal toxicity remains a huge hurdle for extensive applications of these compounds. Thus, alternative compounds with similar optoelectronic properties need to be developed. Bismuth possesses electronic structure similar to that of lead with the presence of ns2 electrons that exhibit rich structural variety as well as interesting optical and electronic properties. Herein, we critically assess Cs3Bi2I9 as a candidate for thin-film solar cell absorber. Despite a reasonable optical band gap (∼2 eV) and absorption coefficient, the power conversion efficiency of the Cs3Bi2I9 mesoscopic solar cells was found to be severely lacking, limited by the poor photocurrent density. The efficiency of the Cs3Bi2I9 solar cell can be slightly improved by changing the stoichiometry of the precursor...

Poor Photovoltaic Performance of Cs3Bi2I9: An Insight through First-Principles Calculations

Abstract: Bismuth-based halide perovskite derivatives have now attracted huge attention for photovoltaic (PV) applications after the unparalleled success of lead-based halide perovskites. However, the performances of PV devices based on these compounds are poor, despite theoretical predictions. In this Article, we have investigated the electronic structure and defect formation energies of Cs3Bi2I9 using density functional theory (DFT) calculations. The calculated electronic bandstructure indicates an indirect bandgap and high carrier effective masses. Our calculations reveal a large stability region for this compound; however, deep level defects are quite prominent. Even the varying chemical potentials from the stoichiometric region do not eliminate the presence of deep defects, ultimately limiting photovoltaic efficiencies.

High-throughput Computational Study of Halide Double Perovskite Inorganic Compounds

Abstract: Double perovskite halides are a class of materials with diverse chemistries that are amenable to solution-based synthesis routes, and display a range of properties for a variety of potential applic...

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...

Toward Lead-Free Perovskite Solar Cells

Abstract: Since the first reports of solar cells with power conversion efficiencies around 10% in 2012, the science and technology of perovskite photovoltaics has been progressing at an unprecedented rate. The current certified record efficiency of 22.1% makes perovskites the first solution-processable technology to outperform multicrystalline and thin-film silicon. For this technology to be deployed on a large scale, the two main challenges that need to be addressed are the material stability and the toxicity of lead. In particular, while lead is allowed in photovoltaic modules, it would be desirable to find alternatives which retain the unique optoelectronic properties of lead halide perovskites. Here we offer our perspective on the most exciting developments in the materials science of new halide perovskites, with an emphasis on alternatives to lead. After surveying recent developments of new perovskites and perovskite-related materials, we highlight the potential of halide double perovskites. This new family of...

An overview on enhancing the stability of lead halide perovskite quantum dots and their applications in phosphor-converted LEDs

Abstract: Beyond the unprecedented success achieved in photovoltaics (PVs), lead halide perovskites (LHPs) have shown great potential in other optoelectronic devices. Among them, nanometer-scale perovskite quantum dots (PQDs) with fascinating optical properties including high brightness, tunable emission wavelength, high color purity, and high defect tolerance have been regarded as promising alternative down-conversion materials in phosphor-converted light-emitting diodes (pc-LEDs) for lighting and next-generation of display technology. Despite the promising applications of perovskite materials in various fields, they have received strong criticism for the lack of stability. The poor stability has also attracted much attention. Within a few years, numerous strategies towards enhancing the stability have been developed. This review summarizes the mechanisms of intrinsic- and extrinsic-environment-induced decomposition of PQDs. Simultaneously, the strategies for improving the stability of PQDs are reviewed in detail, which can be classified into four types: (1) compositional engineering; (2) surface engineering; (3) matrix encapsulation; (4) device encapsulation. Finally, the challenges for applying PQDs in pc-LEDs are highlighted, and some possible solutions to improve the stability of PQDs together with suggestions for further improving the performance of pc-LEDs as well as the device lifetime are provided.

Dimensional tailoring of hybrid perovskites for photovoltaics

Abstract: Hybrid perovskites are currently one of the most active fields of research owing to their enormous potential for photovoltaics. The performance of 3D hybrid organic–inorganic perovskite solar cells has increased at an incredible rate, reaching power conversion efficiencies comparable to those of many established technologies. However, the commercial application of 3D hybrid perovskites is inhibited by their poor stability. Relative to 3D hybrid perovskites, low-dimensional — that is, 2D — hybrid perovskites have demonstrated higher moisture stability, offering new approaches to stabilizing perovskite-based photovoltaic devices. Furthermore, 2D hybrid perovskites have versatile structures, enabling the fine-tuning of their optoelectronic properties through compositional engineering. In this Review, we discuss the state of the art in 2D perovskites, providing an overview of structural and materials engineering aspects and optical and photophysical properties. Moreover, we discuss recent developments along with the main limitations of 3D perovskites and assess the advantages of 2D perovskites over their 3D parent structures in terms of stability. Finally, we review recent achievements in combining 3D and 2D perovskites as an approach to simultaneously boost device efficiency and stability, paving the way for mixed-dimensional perovskite solar cells for commercial applications. Combining low-dimensional and 3D perovskites is a promising approach to achieve stable and efficient solar cells. In this Review, we discuss the structural, optical and photophysical properties of low-dimensional perovskites, compare the stability and efficiency of 2D and 3D perovskite devices, and consider 2D/3D composites as a strategy to increase the stability of perovskite solar cells.

White-Light Emission from Layered Halide Perovskites.

Abstract: ConspectusWith nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400–700 nm) would obviate these problems.In 2014, we described broadband white-light emission upon near-UV excita...