Browsing by Author "Subarna Pramanik"

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Enhancement in photo-response of CuZnS nanocrystals-based photodetector using asymmetric work function electrodes
(Elsevier B.V., 2024) Sandeep Dahiya; Sobhan Hazra; Utkarsh Pandey; Subarna Pramanik; Pardeep Dahiya; Satya Veer Singh; Nikita Kumari; Bhola Nath Pal
In this study, an efficient visible light photodetector has been fabricated by using heavy metal-free CuZnS Nanocrystals with average particle size of 13 ± 1 nm and has been synthesized by a microwave (MW) assisted synthesis technique. The optical band gap of this nanocrytstal is ∼1.7 eV and has an absorbance spectra ranging from 300 to700 nm. This low bandgap nanocrystals has been used to fabricate a photoconductor device with a CuZnS/ZnO bilayer structure. Besides, the device performance has been enhanced by using an asymmetric work-function lateral electrodes. The work-function difference between the electrodes gives a driven voltage between the electrodes, which allows faster collection of charge carriers from the device. As a consequence, a significant photocurrent is generated by the device even without any external bias. The self-biased (at 0 V) external quantum efficiency (EQE) of this device is ∼ 4 % (at 430 nm) whereas this value reaches ∼ 20 % under 2 V external bias. The device possesses the responsivity (Rλ) and detectivity (D) of 8.8 A/W and 3.8 × 1012 Jones at 320 nm respectively under 2 V external bias. © 2024 Elsevier B.V.
Piezopotential Gated Self-Biased Conducting Polymer-Based Flexible Transistor for Mechanical Energy Harvesting Device
(American Chemical Society, 2025) Utkarsh S. Pandey; Sandeep Dahiya; Rajarshi Chakraborty; Subarna Pramanik; Sobhan Hazra; Bhola Nath Pal
A self-biased thin-film transistor (TFT) has been fabricated by using poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) as a conducting channel that works as an efficient mechanical energy harvesting device. The self-biasing of this top-gated TFT has been accomplished through the integration of two voltage sources within the device structure, which are essential for its operation. The LiF/Al and MoO3/Ag electrodes serve as the source and drain, respectively, of this TFT that has a work-function difference of ∼−1.16 eV, which works as the drain bias (VD). The poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) thin film that has been employed as a gate dielectric generates a piezo-potential due to the application of external pressure and works as gate bias (VG) of this TFT. The unique feature of this device is its prolonged electrical power generation in DC form during the application of mechanical force that enables us to measure its mechanical-to-electrical power conversion energy accurately. The extracted power conversion efficiencies of hard and flexible (flat) substrate-based TFTs are 0.4 and 1.9%, respectively. Interestingly, the conversion efficiency of a flexible TFT increases with bending and can reach up to 33% which is unusually high for a mechanical energy harvesting device. In addition, electrical characterization of these devices shows transistor-like behavior with an On-Off ratio and subthreshold swing of 2 × 102 and 5.88 N/decade, respectively, for hard substrate, while on a flexible substrate, these values are 1 × 104 and 1.35 N/decade, respectively. © 2025 American Chemical Society.