Author

Other affiliations: Alagappa University
Bio: Padinhare Cholakkal Harikesh is an academic researcher from Nanyang Technological University. The author has contributed to research in topic(s): Perovskite (structure) & Passivation. The author has an hindex of 12, co-authored 24 publication(s) receiving 511 citation(s). Previous affiliations of Padinhare Cholakkal Harikesh include Alagappa University.

##### Papers
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TL;DR: In this article, Rb can template the formation of the desired layered phase irrespective of processing methodologies, enabling the demonstration of efficient lead-free perovskite solar cells.
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.

197 citations

Journal ArticleDOI
, Bo Wu1, Arramel2

42 citations

Journal ArticleDOI
, Wei Xie1
TL;DR: 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...
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...

41 citations

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TL;DR: In this article, the perovskite surface was passivated with a hydrophobic fluorinated organic salt, namely, pentafluoropropylamonium iodide (PFPAI), which not only narrowed the band gap but also contributed toward the modulation of surface and electronic properties of the resulting film.
Abstract: Despite the high-quality films achieved with triple-cation perovskites, the deviation from an optimized band gap by virtue of Shockley–Queisser estimation signifies consequential light absorption losses in this system. Herein, it is shown that, by passivating the perovskite surface with a hydrophobic fluorinated organic salt, namely, pentafluoropropylamonium iodide (PFPAI), not only is the band gap narrowed but the process also contributes toward the modulation of surface and electronic properties of the resulting film. The cumulative effect of these factors promotes the enhancement in the power conversion efficiency (PCE) and moisture stability of the perovskite solar cells (PSCs) fabricated with the PFPAI-passivated films. Suppression of surface defects and mitigation of interfacial charge recombination in the treated film are in good agreement with the longer photoluminescence (PL) decay lifetime observed. The PFPAI-passivated PSC afforded a PCE of 16.6% with good ambient stability, evidenced by minima...

35 citations

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TL;DR: In this paper, a solution-processed aluminium indium (AlIn)-TiO2 compact layer was used as a highly effective electron transport layer (ETL) to achieve outstanding performance of perovskite solar cells.
Abstract: Among the next-generation photovoltaic technologies, perovskite solar cells have attracted significant attention and interest. In addition to the perovskite absorber component, the adjacent layers within the stack play decisive roles in the stability and overall power conversion efficiency (PCE) of a device. In this study, we demonstrated the use of a solution-processed aluminium indium (AlIn)-TiO2 compact layer as a highly effective electron transport layer (ETL) to achieve outstanding performance of perovskite solar cells; our results showed that the incorporation of AlIn into the TiO2 layer allowed better energy band alignment of the ETL-perovskite interface, improved the transparency, and enhanced the conductivity as compared to the case of pristine TiO2. Via co-doping these trivalent metals, an enhancement in voltage, current density, and even fill factor was observed. In addition, the results obtained from electrochemical impedance spectroscopy (EIS) revealed that the AlIn-TiO2-based device exhibited larger recombination resistance, which significantly benefited the performance of the devices. As a result, the optimized AlIn-TiO2 ETL device attained the surpassing PCE of 19% as compared to the pristine TiO2 solar device having the PCE of 16.67%.

27 citations

##### Cited by
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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...

949 citations

Journal ArticleDOI
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...

580 citations

Journal ArticleDOI
, Jia Guo1, Qi Li2, Qi Li3
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.

408 citations

Posted Content
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.

367 citations

Journal ArticleDOI

TL;DR: In this article, the authors show that perovskite-based solar cells should have a high electronic dimensionality, because of barriers to isotropic current flow, enhanced electron/hole effective masses and fundamentally deeper defect states.
Abstract: Searching for promising nontoxic and air-stable perovskite absorbers for solar cell applications has drawn extensive attention. Here, we show that a promising perovskite absorber should exhibit a high electronic dimensionality. Semiconductors that exhibit a high structural dimensionality, but a low electronic dimensionality have less promise as an absorber, because of barriers to isotropic current flow, enhanced electron/hole effective masses and fundamentally deeper defect states (more effective at causing recombination). Our concept accounts for the device performance of the perovskite-based solar cells reported in literature so far.

363 citations