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Junctionless tunneling field-effect transistor (JL-TFET) is an excellent potential alternative to conventional MOSFET and TFET due to the lack of a steep doping profile, which makes it easier to fabricate. JL-TFET not only offers a lower subthreshold swing (SS) compared to MOSFET, but mitigates the low on-current problem associated with conventional TFET. The DC and analog characteristics of JL-TFET can be further improved by design modifications. In this research, we have presented two novel structures of JL-TFET: stimulated n-pocket JL-TFET (SNPJL-TFET) and SNPJL-TFET with heterogeneous gate dielectric. The performance of these devices has been gauged against conventional JL-TFET. Both novel structures exhibit excellent performance including point SS around 20 mV/dec, high ION/IOFF in the order of 1014 and lower threshold voltage (VT). By analyzing RF and linearity parameters such as the transconductance generation factor, FT, transit time, total factor productivity, second-order voltage intercept point, third-order voltage intercept point, third-order input intercept point and third-order intermodulation distortion, it is observed that the proposed devices are more suitable for RF applications since they show superiority in most of the analyzed parameters. [ABSTRACT FROM AUTHOR]

The rapid surge in perovskite solar cell efficiency has necessitated the development of viable metrology techniques during device integration, paving the way for commercialization. Ellipsometry is considered the most appropriate technique for fast and accurate thickness measurement for large scale production. However, a precise and well-calibrated model is a prerequisite for this technique. While ellipsometry of individual device layers has been reported in recent perovskite literature, a comprehensive multilayer modeling approach is thus far unavailable. Perovskite optoelectronic devices generally consist of a six-layer film stack with three transparent layers required for optical absorption in the perovskite layer. Spin casted thin films, now common in this line of research, impart their own difficulties into ellipsometric modeling. Roughnesses at each heterointerface, similarities in optical spectra of transparent layers, and anomalous dispersion of perovskite are just a few of such challenges. In this work, we report the process of building an ellipsometry model from scratch for thickness measurement of methylammonium lead iodide (MAPI) perovskite and indium tin oxide (ITO)/hole transport layer (HTL) bilayer thin film stacks on a glass substrate. Three promising representatives of HTLs (CuI, Cu2O, and PEDOT:PSS) were studied. The models were extended to measure the individual layer thicknesses of the MAPI/HTL/ITO film stack on a glass substrate using the models developed for individual layers. Optical constants of all the representative thin films were thus extracted for a wide wavelength range (300 nm–900 nm). [ABSTRACT FROM AUTHOR]

The nucleation and growth of organic–inorganic hybrid perovskite films induced by the molar ratio of precursor components and their role in optoelectronic performance are investigated. Lead iodide (PbI2), methylammonium acetate (MAAc) and methylammonium iodide (MAI) mixed in different ratios were used as starting precursors for active layer deposition. While all the as cast films showed the presence of a precursor intermediate (PbIx·MAAc·MAI), the films derived from 1 : 1 : 1 and 1 : 0.5 : 1 ratios also exhibited crystallization of the perovskite (CH3NH3PbI3) phase during the spin coating process. The nucleation and crystallization of the perovskite phase in films derived from the equimolar precursor ratio were found to be the key to growing larger, smoother and single crystalline grains along the thickness leading to higher carrier lifetimes. Perovskite solar cells fabricated utilizing such a morphology showed a much higher power conversion efficiency irrespective of the active layer thickness. Furthermore, methyl ammonium bromide based perovskite light emitting diodes were also fabricated using the aforementioned equimolar precursor ratio which exhibited superior device performance compared to diodes with active layers derived from other precursor ratios. This work highlights a facile deposition technique and growth mechanism to attain reproducible, low cost and high-performance perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]

Organohalide lead (hybrid) perovskites have emerged as competitive semiconducting materials for photovoltaic devices due to their high performance and low cost. To further the understanding and optimization of these materials, solution-based methods for interrogating and modifying perovskite thin films are needed. In this work, we report a hydrofluoroether (HFE) solvent-based electrolyte for electrochemical processing and characterization of organic-inorganic trihalide lead perovskite thin films. Organic perovskite films are soluble in most of the polar organic solvents, and thus until now, they were not considered suitable for electrochemical processing. We have enabled electrochemical characterization and demonstrated a processing toolset for these materials utilizing highly fluorinated electrolytes based on a HFE solvent. Our results show that chemically orthogonal electrolytes based on HFE solvents do not dissolve organic perovskite films and thus allow electrochemical characterization of the electronic structure, investigation of charge transport properties, and potential electrochemical doping of the films with in situ diagnostic capabilities. [ABSTRACT FROM AUTHOR]

Transparency loss and excess excitation loss are responsible for relatively lower conversion efficiency of single junction solar cell. One way to reduce these two losses is to use multijunction solar cell. In this research InxGa1-xN based single, double and triple junction solar cells were simulated employing AMPS-1D simulator. The band gap of each layer depends on the composition percentage of InN and GaN within InxGa1-xN. In this simulation the authors found 24.51, 33.89, and 42.12% efficiencies for single, double and triple junctions, respectively. [ABSTRACT FROM AUTHOR]