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Ajay Kumar Jena

Bio: Ajay Kumar Jena is an academic researcher from Toin University of Yokohama. The author has contributed to research in topics: Perovskite (structure) & Photovoltaics. The author has an hindex of 21, co-authored 46 publications receiving 2412 citations. Previous affiliations of Ajay Kumar Jena include Indian Institute of Technology Bombay.

Papers published on a yearly basis

Papers
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Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this paper, the performance degradation of perovskite solar cells at high temperature (60, 80, 100 and 120 °C) and under a humid (30-50% relative humidity) environment, and then tried to reuse the perov-skite films from the degraded cells to recover the cell efficiency so as to avoid dumping of Pb-waste into the environment.
Abstract: As the long-term stability and toxicity of Pb are two profound concerns for the commercialization of Pb-based perovskite solar cells, we have undertaken this study to understand the performance degradation of perovskite solar cells at high temperature (60, 80, 100 and 120 °C) and under a humid (30–50% relative humidity) environment, and then tried to reuse the perovskite films from the degraded cells to recover the cell efficiency so as to avoid dumping of Pb-waste into the environment. As found in this study, the performance of MAPbI3 (MA = CH3NH3) cells using spiro-OMeTAD as the hole transport material (HTM) deteriorated mainly not due to the degradation of the perovskite but because of the modification of the interface between the perovskite and spiro-OMeTAD at high temperature. In addition, the spiro-OMeTAD layer underwent a severe morphological deformation at high temperature, showing large voids in it, which reduced the cell performance further. However, despite the complete reconversion of PbI2 to perovskite and the replacement of the degraded spiro-OMeTAD film with a fresh layer in the MAPbI3 cells, the cell performance was not recovered to the initial value because the modified perovskite/spiro-OMeTAD interface became worse after recycling. The thermal stability and performance recovery upon recycling were found to depend on the composition of the perovskite; faster degradation of MAPbI3 cells with a slight excess of MAI and better stability of cells not containing MA (FA0.85Cs0.15PbI3, FA = CH(NH2)2) indicated certain involvement of MA+ ions in the alteration of the perovskite/spiro-OMeTAD interface. Unlike the heat-treatment case, MAPbI3 cells, when exposed to a humid environment, degraded significantly to PbI2 and the reconversion of this PbI2 to perovskite followed by deposition of a fresh spiro-OMeTAD layer increased the cell performance but it did not recover to the initial value. This poor recovery in these cells was due to inefficient carrier transport that resulted in a lower photocurrent in the recycled devices.

198 citations

Journal ArticleDOI
TL;DR: In this paper, the photoactive black phase (α-CsPbI3) was stabilized by incorporating Eu3+ (EuCl3) into CsPb-I3:xEu cells with 5-6 mol % of Eu.
Abstract: Although inorganic perovskite, CsPbI3, shows superior thermal stability over organic–inorganic hybrid perovskites, stabilization of the photoactive black phase (α-CsPbI3) of CsPbI3 perovskite at room temperature and in ambient conditions has remained a challenge. Herein, we present a method of stabilizing the α-CsPbI3 at lower annealing temperature (85 °C) by incorporation of Eu3+ (EuCl3) into CsPbI3, which prevents the black to the yellow phase (δ-CsPbI3) transformation in ambient air (room temperature) for a reasonably long time (>30 days). Photovoltaic performance of this Eu-stabilized α-CsPbI3, as assessed in planar heterojunction solar cells (FTO/TiO2/CsPbI3:xEu/spiro-OMeTAD/Au), shows a power conversion efficiency above 6% on backward scan (stabilized power output above 4%) for CsPbI3:xEu cells with 5–6 mol % of Eu, while CsPbI3 without Eu, as expected, shows no photovoltaic property at all. However, as the cell stability was found to be affected by composition of organic hole transport material (HT...

177 citations

Journal ArticleDOI
TL;DR: In this article, the use of the Ti3C2 MXene in organic-inorganic lead halide perovskite solar cells (PSCs) was explored, and the electron transport layers were used as ETLs in low-temperature processed planar-structured PSCs.
Abstract: MXenes, a class of two-dimensional (2D) transition metal carbides and nitrides, have a wide range of potential applications due to their unique electronic, optical, plasmonic, and other properties. Herein, we explore the use of the Ti3C2 MXene in organic–inorganic lead halide perovskite solar cells (PSCs). SnO2–Ti3C2 MXene nanocomposites with different contents of Ti3C2 (0, 0.5, 1.0, 2.0, and 2.5 wt‰) were used as electron transport layers (ETLs) in low-temperature processed planar-structured PSCs. Mixing SnO2 with 1.0 wt‰ Ti3C2 effectively increases the power conversion efficiency (PCE) from 17.23% to 18.34%, whereas the device prepared with pristine Ti3C2 as the ETL achieves a PCE of 5.28%. Photoluminescence and electrochemical impedance spectroscopy results reveal that metallic Ti3C2 MXene nanosheets provide superior charge transfer paths, enhancing electron extraction, electron mobility, and decreasing the electron transfer resistance at the ETL/perovskite interface, and thus leading to higher photocurrents. This work proposes a new field of application for MXenes and a promising method to increase the efficiency of solar cells.

153 citations


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Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: A reversible photo-induced instability has been found in mixed-halide photovoltaic perovskites that limits the open circuit voltage in solar cells.
Abstract: We report on reversible, light-induced transformations in (CH3NH3)Pb(BrxI1−x)3. Photoluminescence (PL) spectra of these perovskites develop a new, red-shifted peak at 1.68 eV that grows in intensity under constant, 1-sun illumination in less than a minute. This is accompanied by an increase in sub-bandgap absorption at ∼1.7 eV, indicating the formation of luminescent trap states. Light soaking causes a splitting of X-ray diffraction (XRD) peaks, suggesting segregation into two crystalline phases. Surprisingly, these photo-induced changes are fully reversible; the XRD patterns and the PL and absorption spectra revert to their initial states after the materials are left for a few minutes in the dark. We speculate that photoexcitation may cause halide segregation into iodide-rich minority and bromide-enriched majority domains, the former acting as a recombination center trap. This instability may limit achievable voltages from some mixed-halide perovskite solar cells and could have implications for the photostability of halide perovskites used in optoelectronics.

1,549 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarize what is known and unknown about charge transport in HOIPs, with particular emphasis on their advantages as photovoltaic materials and highlight the fundamental questions that need to be addressed regarding the charge-transport properties of these materials.
Abstract: Solution-processed hybrid organic–inorganic perovskites (HOIPs) exhibit long electronic carrier diffusion lengths, high optical absorption coefficients and impressive photovoltaic device performance. Recent results allow us to compare and contrast HOIP charge-transport characteristics to those of III–V semiconductors — benchmarks of photovoltaic (and light-emitting and laser diode) performance. In this Review, we summarize what is known and unknown about charge transport in HOIPs, with particular emphasis on their advantages as photovoltaic materials. Experimental and theoretical findings are integrated into one narrative, in which we highlight the fundamental questions that need to be addressed regarding the charge-transport properties of these materials and suggest future research directions. The charge transport properties of hybrid organic—inorganic perovskites, which can explain their excellent photovoltaic performance, are reviewed through an integrated summary of experimental and theoretical findings. The potential origins of these properties are discussed and future research directions are indicated.

1,161 citations

Journal ArticleDOI
TL;DR: Recommendations are made on how accelerated testing should be performed to rapidly develop solar cells that are both extraordinarily efficient and stable.
Abstract: This review article examines the current state of understanding in how metal halide perovskite solar cells can degrade when exposed to moisture, oxygen, heat, light, mechanical stress, and reverse bias. It also highlights strategies for improving stability, such as tuning the composition of the perovskite, introducing hydrophobic coatings, replacing metal electrodes with carbon or transparent conducting oxides, and packaging. The article concludes with recommendations on how accelerated testing should be performed to rapidly develop solar cells that are both extraordinarily efficient and stable.

962 citations