Publications by authors named "Narayanaswamy Kamatham"

In this contribution, doping of oriented thin films is investigated for three PBTTT polymers bearing different side chains including linear alkyl ─(CH)─H, single ether ─(CH)─O─(CH)─H and alkyl-siloxane ─(CH)─(Si(CH)O)─Si(CH) A combination of transmission electron microscopy, polarized UV-vis-NIR spectroscopy and transport measurements helps uncover the essential role of the chemical nature of side chains on the efficacy of the doping and on the resulting thermoelectric performances in oriented PBTTT films. Siloxane side chains help to reach record alignment level of PBTTT with dichroic ratio beyond 50 for an optimized rubbing temperature but they impede effective doping of PBTTT crystals with FTCNNQ, resulting in very poor TE properties. By contrast, doping the amorphous phase of all three PBTTTs with magic blue (MB) results in excellent TE performances.

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Two novel BODIPY dyes, BOC3 and BC12, were synthesized with variable alkyl chains at terminal amide functional units. BC12, featuring a longer alkyl chain (-C12H25), formed a gel compared to BOC3, which has a shorter alkyl chain (-CH2OCH3), due to supra molecular self-assembly in film. Both dyes exhibited absorption peaks around 530 nm in the visible region, with a red shift of about 30 nm in the film state, essential for organic electronic applications.

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Article Synopsis
  • Two-dimensional perovskites with organic fluorophores can serve as effective emitters for LEDs, though previous designs had low external quantum efficiencies (EQEs).
  • This study increased EQE to about 10% by selecting a fluorophore that complements the energy levels of the perovskite structure, improving exciton formation and avoiding energy losses.
  • Enhanced light-outcoupling efficiency due to light scattering in the polycrystalline perovskite layer also contributes to effective electroluminescence, paving the way for high-performance, low-cost LED products.
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We report the design of novel medium bandgap nonfullerene small molecule acceptor NFSMA with A-π-A-π-A architecture, with the molecular engineering of this material comprising a strong electron-accepting backbone unit DPP (A) as the acceptor, which is attached to the dicyanomethylene-3-hexylrhodanine (A) acceptor via a furan (π-spacer) linker. We systematically studied its structural and optoelectronic properties. The incorporation of dicyanomethylene-3-hexylrhodanine and furan enhance the light absorption and electrochemical properties by extending π-conjugation and is anticipated to improve by decreasing the LUMO level.

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Herein, the synthesis of the novel acceptor-donor-acceptor (A-D-A)-structured small molecule Si-PO-2CN based on dithienosilole (DTS) as building block flanked by electron-rich phenoxazine (POZ) units, which are terminated with dicyanovinylene, is presented. Si-PO-2CN showed unique electrochemical and photophysical properties and has been successfully employed in perovskite solar cells (PSCs) as well as in bulk heterojunction organic solar cells (OSCs). The PSCs fabricated with dopant-free Si-PO-2CN as hole-transport material (HTM) exhibited a power conversion efficiency (PCE) of 14.

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Synthesis and photophysical characterizations of two novel small molecules and with D-A-D molecular structure consisting of squaraine as central unit and benzothiophene and benzofuran as end groups are being reported. Apart from very sharp and intense light absorption by these molecular sensitizers in near-infrared (NIR) wavelength region, their possibility as small molecular organic semiconductor was also explored after fabricating organic field-effect transistors (OFETs). Results obtained from photophysical, electrochemical, and quantum chemical studies were combined to elucidate the structural and optoelectronic properties.

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Solution-processable D-π-A-π-D structured two organic small molecules bearing thienyl diketopyrrolopyrrole (TDPP) and furanyl diketopyrrolopyrrole (FDPP) as central acceptor units and cyano on the π-bridge and phenothiazine as the terminal donor units, coded as and , are designed and synthesized. The C-H arylation and Suzuki coupling protocols have been adopted for synthesizing the molecules. Solution-processed organic solar cells (OSCs) were constructed with these molecules as the donors and phenyl-C-butyric acid methyl ester as the acceptor yielding power conversion efficiencies (PCE) of 4.

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