Author: Valligatla, Sreeramulu × DDC: 540 ×

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    A thiazolo[5,4-: D] thiazole-bridged porphyrin organic framework as a promising nonlinear optical material
    (London : Royal Society of Chemistry (RSC), 2019) Samal, Mahalaxmi; Valligatla, Sreeramulu; Saad, Nabil A.; Rao, M. Veeramohan; Rao, D. Narayana; Sahu, Rojalin; Biswal, Bishnu P.
    Porphyrin-based porous organic frameworks are an important group of materials gaining interest due to their structural diversity and distinct opto-electronic properties. However, these materials are seldom explored for nonlinear optical (NLO) applications. In this work, we investigate a thiazolo[5,4-d]thiazole-bridged porous, porphyrin framework (Por-TzTz-POF) with promising NLO properties. The planar TzTz moiety coupled with integrated porphyrin units enables efficient π-conjugation and charge distribution in the Por-TzTz-POF resulting in a high nonlinear absorption coefficient (β = 1100 cm GW-1) with figure of merit (FoM) σ1/σ0 = 5571, in contrast to analogous molecules and material counterparts e.g. metal-organic frameworks (MOFs; β = ∼0.3-0.5 cm GW-1), molecular porphyrins (β = ∼100-400 cm GW-1), graphene (β = 900 cm GW-1), and covalent organic frameworks (Por-COF-HH; β = 1040 cm GW-1 and FoM = 3534). This journal is © The Royal Society of Chemistry.
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    Fast-Response Micro-Phototransistor Based on MoS2/Organic Molecule Heterojunction
    (Basel : MDPI, 2023) Andleeb, Shaista; Wang, Xiaoyu; Dong, Haiyun; Valligatla, Sreeramulu; Saggau, Christian Niclaas; Ma, Libo; Schmidt, Oliver G.; Zhu, Feng
    Over the past years, molybdenum disulfide (MoS2) has been the most extensively studied two-dimensional (2D) semiconductormaterial. With unique electrical and optical properties, 2DMoS2 is considered to be a promising candidate for future nanoscale electronic and optoelectronic devices. However, charge trapping leads to a persistent photoconductance (PPC), hindering its use for optoelectronic applications. To overcome these drawbacks and improve the optoelectronic performance, organic semiconductors (OSCs) are selected to passivate surface defects, tune the optical characteristics, and modify the doping polarity of 2D MoS2. Here, we demonstrate a fast photoresponse in multilayer (ML) MoS2 by addressing a heterojunction interface with vanadylphthalocyanine (VOPc) molecules. The MoS2/VOPc van der Waals interaction that has been established encourages the PPC effect in MoS2 by rapidly segregating photo-generated holes, which move away from the traps of MoS2 toward the VOPc molecules. The MoS2/VOPc phototransistor exhibits a fast photo response of less than 15 ms for decay and rise, which is enhanced by 3ordersof magnitude in comparison to that of a pristine MoS2-based phototransistor (seconds to tens of seconds). This work offers a means to realize high-performance transition metal dichalcogenide (TMD)-based photodetection with a fast response speed.