Author
Padinhare Cholakkal Harikesh
Other affiliations: Alagappa University
Bio: Padinhare Cholakkal Harikesh is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Perovskite (structure) & Neuromorphic engineering. The author has an hindex of 12, co-authored 24 publications receiving 511 citations. Previous affiliations of Padinhare Cholakkal Harikesh include Alagappa University.
Papers
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TL;DR: It is shown, for the first time, the possibility of engineering the carriers in halide perovskite via metal cation transmutation to successfully form intrinsic p- and n-type materials and that this material possesses a direct-indirect bandgap enabling high absorption coefficient, extended carrier lifetimes >100 ns, and low trap densities similar to lead halideperovskites.
Abstract: Creating defect tolerant lead-free halide perovskites is the major challenge for development of high-performance photovoltaics with nontoxic absorbers. Few compounds of Sn, Sb, or Bi possess ns2 electronic configuration similar to lead, but their poor photovoltaic performances inspire us to evaluate other factors influencing defect tolerance properties. The effect of heavy metal cation (Bi) transmutation and ionic migration on the defects and carrier properties in a 2D layered perovskite (NH4 )3 (Sb(1-x) Bix )2 I9 system is investigated. It is shown, for the first time, the possibility of engineering the carriers in halide perovskites via metal cation transmutation to successfully form intrinsic p- and n-type materials. It is also shown that this material possesses a direct-indirect bandgap enabling high absorption coefficient, extended carrier lifetimes >100 ns, and low trap densities similar to lead halide perovskites. This study also demonstrates the possibility of electrical poling to induce switchable photovoltaic effect without additional electron and hole transport layers.
22 citations
TL;DR: In this paper, a solution-processed zinc oxide and zinc tin oxide (ZTO) films were used as highly efficient electron transport layer (ETL) for perovskite solar cells.
21 citations
TL;DR: In this article, the feasibility of all-ambient-processing of perovskite solar cells and evaluated their photovoltaic performance was systematically studied and it was shown that phase-pure crystalline tetragonal MAPbI3 films are instantly formed in ambient air at room temperature by a two-step spin coating process, undermining the need for dry atmosphere and postannealing.
19 citations
TL;DR: In this article, a lead-free halide perovskite semiconductors are necessary due to the atmospheric instability and lead toxicity associated with the 3D lead-halide pervskites.
Abstract: Lead-free halide perovskite semiconductors are necessary due to the atmospheric instability and lead toxicity associated with the 3D lead halide perovskites. However, a stable lead-free perovskite ...
18 citations
TL;DR: A general summary of the structural and optoelectronic characteristics of halide perovskite-based neuromorphic devices can be found in this paper, where the authors provide insights into the underlying switching mechanisms.
Abstract: Hybrid organic-inorganic halide perovskites have been recently explored as memristive devices that can be programmed to two or more stable conductance states for analog computing. The wide variety and range of optoelectronic phenomena these materials portray offer immense potential to develop scaled-in neuromorphic devices and architectures with multibit memory storage and multimodal accessibility. This article provides a general summary of the structural and optoelectronic characteristics of this material class that could be utilized for neuromorphic computing, discusses insights into the underlying switching mechanisms, and reviews recent developments in the field of halide perovskite-based neuromorphic devices.
15 citations
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TL;DR: The fundamentals, recent research progress, present status, and 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 are described.
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...
1,720 citations
TL;DR: In this paper, the halide double perovskites have been proposed as a solution-processable technology to outperform multicrystalline and thin-film silicon for photovoltaics.
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...
783 citations
TL;DR: Recent progress on lead-free PSCs is reviewed in terms of the theoretical insight and experimental explorations of the crystal structure of lead- free perovskite, thin film deposition, and device performance.
Abstract: Organic-inorganic hybrid halide perovskites (e.g., MAPbI3 ) have recently emerged as novel active materials for photovoltaic applications with power conversion efficiency over 22%. Conventional perovskite solar cells (PSCs); however, suffer the issue that lead is toxic to the environment and organisms for a long time and is hard to excrete from the body. Therefore, it is imperative to find environmentally-friendly metal ions to replace lead for the further development of PSCs. Previous work has demonstrated that Sn, Ge, Cu, Bi, and Sb ions could be used as alternative ions in perovskite configurations to form a new environmentally-friendly lead-free perovskite structure. Here, we review recent progress on lead-free PSCs in terms of the theoretical insight and experimental explorations of the crystal structure of lead-free perovskite, thin film deposition, and device performance. We also discuss the importance of obtaining further understanding of the fundamental properties of lead-free hybrid perovskites, especially those related to photophysics.
533 citations
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TL;DR: In this article, the authors proposed a new class of halide double perovskites, where the B$^{3+}$ and B$€ 2+} cations are In$^{2+} and Ag$^{+}, respectively.
Abstract: A$_2$BB$^\prime$X$_6$ halide double perovskites based on bismuth and silver have recently been proposed as potential environmentally-friendly alternatives to lead-based hybrid halide perovskites. In particular, Cs$_2$BiAgX$_6$ (X = Cl, Br) have been synthesized and found to exhibit band gaps in the visible range. However, the band gaps of these compounds are indirect, which is not ideal for applications in thin film photovoltaics. Here, we propose a new class of halide double perovskites, where the B$^{3+}$ and B$^{+}$ cations are In$^{3+}$ and Ag$^{+}$, respectively. Our first-principles calculations indicate that the hypothetical compounds Cs$_2$InAgX$_6$ (X = Cl, Br, I) should exhibit direct band gaps between the visible (I) and the ultraviolet (Cl). Based on these predictions, we attempt to synthesize Cs$_2$InAgCl$_6$ and Cs$_2$InAgBr$_6$, and we succeed to form the hitherto unknown double perovskite Cs$_2$InAgCl$_6$. X-ray diffraction yields a double perovskite structure with space group $Fm\overline{3}m$. The measured band gap is 3.3 eV, and the compound is found to be photosensitive and turns reversibly from white to orange under ultraviolet illumination. We also perform an empirical analysis of the stability of Cs$_2$InAgX$_6$ and their mixed halides based on Goldschmidt's rules, and we find that it should also be possible to form Cs$_2$InAg(Cl$_{1-x}$Br$_{x}$)$_6$ for $x<1$. The synthesis of mixed halides will open the way to the development of lead-free double perovskites with direct and tunable band gaps.
519 citations
TL;DR: Reviews on the theoretical understanding of the electronic, optical, and defect properties of Pb and Pb-free halide perovskites andperovskite derivatives are provided, as well as the experimental results available in the literature.
Abstract: Despite the exciting progress on power conversion efficiencies, the commercialization of the emerging lead (Pb) halide perovskite solar cell technology still faces significant challenges, one of which is the inclusion of toxic Pb. Searching for Pb-free perovskite solar cell absorbers is currently an attractive research direction. The approaches used for and the consequences of Pb replacement are reviewed herein. Reviews on the theoretical understanding of the electronic, optical, and defect properties of Pb and Pb-free halide perovskites and perovskite derivatives are provided, as well as the experimental results available in the literature. The theoretical understanding explains well why Pb halide perovskites exhibit superior photovoltaic properties, but Pb-free perovskites and perovskite derivatives do not.
503 citations