Trilok Singh

Effect of Electron Transporting Layer on Bismuth-Based Lead-Free Perovskite (CH3NH3)3 Bi2I9 for Photovoltaic Applications

Methylammonium iodo bismuthate ((CH3NH3)3Bi2I9) (MBI) perovskite is a promising alternative to rapidly progressing hybrid organic-inorganic lead perovskites because of its better stability and low toxicity compared to lead-based perovskites. Solution-processed perovskite fabricated by single-step spin-coating and subsequent heating produced polycrystalline films of hybrid perovskite (CH3NH3)3Bi2I9), whose morphology was influenced drastically by the nature of substrates. The optical measurements showed a strong absorption band around 500 nm. The devices made on anatase TiO2 mesoporous layer showed good performance with current density over 0.8 mA cm(-2) while the devices on brookite TiO2 layer and planar (free of porous layer) was inefficient. However, all the MBI devices were stable to ambient conditions for more than 10 weeks.

Role of Metal Oxide Electron-Transport Layer Modification on the Stability of High Performing Perovskite Solar Cells.

Organic-inorganic hybrid perovskite light absorbers have recently emerged as a holy grail for next generation thin-film photovoltaics with excellent optoelectronics properties and low fabrication cost. In a very short span of time, we have witnessed a pronounced and unexpected progress in organic- inorganic perovskite solar cells (PSCs) with a vertical rise in power conversion efficiency from 3.8 to 22.1u2009%. In this manuscript we focus specifically on the recent development of metal oxide-based electron-transporting layer (ETL) modification for high performing PSCs and their stability. This review highlights various methodologies to modify existing compact/scaffold layers for improving device performance and stability. Various aspects of the ETL are discussed with different metal oxide compact layers in their relation to modification in mesoporous layers towards the design of a cell structure with high performance and stability.

Photovoltaic enhancement of bismuth halide hybrid perovskite by N-methyl pyrrolidone-assisted morphology conversion

Low toxicity and highly stable methylammonium bismuth iodide (MBI) ((CH3NH3)3Bi2I9) as a solution-processable photovoltaic absorber produces hexagonal non-uniform morphology leading to poor interfacial contacts with the electron and hole transporting layers. Herein, we tuned the morphology of MBI perovskite by bringing in a small amount of N-methyl-2-pyrrolidone (NMP) as a morphology controller into the MBI–DMF solution. The incorporation of various concentrations of NMP into the precursor solution was found to control the rate of crystallization. An optimal low concentration of 2.5% NMP added to the MBI–DMF precursor solution showed a 50% enhancement in short-circuit current (Jsc). The device showed power conversion efficiencies up to 0.31% with high reproducibility. Moreover, the devices were quite stable when exposed to an ambient atmosphere (relative humidity of 50–60%) for 30 days.

Classicalization of inflationary perturbations by collapse models in the light of BICEP2

Inflationary and hence quantum origin of primordial perturbations is on a firmer ground than ever post the BICEP2 observations of primordial gravitational waves. One crucial ingredient of success of this paradigm rests on explaining the observed classicality of cosmological inhomogeinities despite their quantum origin. Although decoherence provides a partial understanding of this issue, the question of single outcome motivates the analysis of quantum collapse models in cosmological context which generically modify the dynamics of primordial perturbations and hence can leave their imprints on observables. We revisit one such recently proposed working model of classicalization by spontaneous collapse cite{Das:2013qwa} in the light of BICEP2 observations to look for possible modifications to tensor power spectra and their implications. We show that it can potentially change the consistency relation of single-field models and a precise measurement of

New Acyclic Chalcogen Bearing Ligands and their Complexation Reactions

n_T

Tuning of perovskite solar cell performance via low-temperature brookite scaffolds surface modifications

and its running could serve as a test of such dynamics in the early universe.

Vapor Annealing Controlled Crystal Growth and Photovoltaic Performance of Bismuth Triiodide Embedded in Mesostructured Configurations

Two (N 3 Se 2) type acyclic Schiff-bases, [{PhSe(CH2)n N=C(CH3)}2C5H3N] (n = 2,3), and their complexes with Cd(II) have been synthesized and characterized. The geometry around central cadmium has been assigned on the basis of physicochemical and spectral studies.Structure of the cadmium complex [PhSe(CH2)3NC(CH3)C5H5N.C(CH3)NH] .CdCl2 has been confirmed by single crystal X-ray diffraction method.

Signatures of spontaneous collapse-dynamics-modified single-field inflation

The nature of metal oxide scaffold played a pivotal role for the growth of high quality perovskites and subsequently facilitates efficient photovoltaics devices. We demonstrate an effective way to fabricate a low-temperature TiO2 brookite scaffold layer with a uniform and pinhole-free layer for enhancing photovoltaic properties of perovskite solar cells. Various concentrations of TiCl4 were used to modify brookite TiO2 for efficient charge generation and fast charge extraction. We observed that the brookite layer with an appropriate TiCl4 treatment possesses a smooth surface with full coverage of the substrates, whereas TiCl4 treatment further improves the contact of the TiO2/perovskite interface which facilitates charge extraction and drastically influenced charge recombination. The surface treated brookite scaffolds perovskite devices showed an improved performance with an average power conversion efficiency more than 17%. The time resolved photoluminescence showed that the treated samples have obvious ...

Quantum to classical transition of inflationary perturbations: Continuous spontaneous localization as a possible mechanism

Low stability of organic-inorganic lead halide perovskite and toxicity of lead (Pb) still remain a concern. Therefore, there is a constant quest for alternative nontoxic and stable light-absorbing materials with promising optoelectronic properties. Herein, we report about nontoxic bismuth triiodide (BiI3) photovoltaic device prepared using TiO2 mesoporous film and spiro-OMeTAD as electron- and hole-transporting materials, respectively. Effect of annealing methods (e.g., thermal annealing (TA), solvent vapor annealing (SVA), and Petri dish covered recycled vapor annealing (PR-VA)) and different annealing temperatures (90, 120, 150, and 180 °C for PR-VA) on BiI3 film morphology have been investigated. As found in the study, grain size increased and film uniformity improved as temperature was raised from 90 to 150 °C. The photovoltaic devices based on BiI3 films processed at 150 °C with PR-VA treatment showed power conversion efficiency (PCE) of 0.5% with high reproducibility, which is, so far, the best PCE reported for BiI3 photovoltaic device employing organic hole-transporting material (HTM), owing to the increase in grain size and uniform morphology of BiI3 film. These devices showed stable performance even after 30 days of exposure to 50% relative humidity, and after 100 °C heat stress and 20 min light soaking test. More importantly, the study reveals many challenges and room (discussed in the details) for further development of the BiI3 photovoltaic devices.

Stabilizing the Efficiency Beyond 20% with a Mixed Cation Perovskite Solar Cell Fabricated in Ambient Air under Controlled Humidity

The observed classicality of primordial perturbations, despite their quantum origin during inflation, calls for a mechanism for quantum-to-classical transition of these initial fluctuations. As literature suggests a number of plausible mechanisms which try to address this issue, it is of importance to seek for concrete observational signatures of these several approaches in order to have a better understanding of the early universe dynamics. Among these several approaches, it is the spontaneous collapse dynamics of Quantum Mechanics which is most viable of leaving discrete observational signatures as collapse mechanism inherently changes the generic Quantum dynamics. We observe in this study that the observables from the scalar sector, i.e. scalar tilt