Asymmetric Electrode-Driven Self-Powered Photodetector Using Cu2-xS Film Karthickraja Ramakrishnan, Y. Ashok Kumar Reddy, B. Ajitha ACS Applied Electronic Materials, 2025 Self-powered photodetectors through asymmetric contact modulation are a simple and efficient approach that has gained a lot of attention because they form an energy gradient in the band gap of the semiconductor. This energy gradient develops the self-assembly of the built-in electric field to separate the electron–hole pairs without any external bias, which facilitates long-term functioning of the device. Copper sulfide (Cu2-xS) is a promising p-type semiconductor for visible-near-infrared photodetectors due to its tunable band gap and electrical properties. In this work, a Cu2-xS-based metal–semiconductor–metal (MSM) photodetector with asymmetric electrodes (Au/Cu2-xS/Ag) is fabricated, and its photodetector properties are measured under visible and near-infrared (NIR) light illuminations. The fabricated Au/Cu2-xS/Ag structured device shows responsivity of 5.66 × 10–3 A/W and 11.24 × 10–3 A/W under visible (λ = 530 nm) and NIR (λ = 980 nm) light illuminations, respectively, even at zero bias. Finally, the obtained results attest that the fabricated self-powered photodetector is highly suitable for modern self-powered optoelectronic applications.
Self-Powered Photodetector Based on p(Cu2O)–n(MoO3) Junction Architecture: Analyzing the Influence of Depletion Region Width on the Photodetector Properties Anibrata Mondal, Karthickraja Ramakrishnan, Sourav Deb, B. Ajitha, Y. Ashok Kumar Reddy ACS Applied Energy Materials, 2025 In this study, the fabrication of the p–n junction photodetector (PD) based on p-type Cu2O and n-type MoO3 semiconductor, which shows a broadband photoresponse (ultraviolet to near-infrared) at self-powered mode, is presented. The thin films are grown through the sputtering technique by varying the depletion region width (DRW) by 2 mm, 3.5 mm, and 5 mm, and the photodetector properties are studied. The fabricated device with a DRW of 3.5 mm, depending on the generation of a stronger electric field, with less recombination of the charge carriers at the depletion region, results in achieving higher photodetector properties. Consequently, the Ag/Cu2O:MoO3/Ag@DRW of the 3.5 mm device shows the highest photocurrent of 16.6 and 39.12 nA under the illumination of 550 and 1000 nm wavelengths. Furthermore, the photodetector properties of the device fabricated on the polyethylene terephthalate (PET) substrate are studied by applying a bias voltage. At 5 V bias voltage and under the illumination of UV light, the Ag/Cu2O:MoO3/Ag@DRW of a 3.5 mm device grown on the PET substrate shows the Rλ of 11.4 μA/W and D* of 1.45 × 106 Jones. Finally, these superior figures of merit of the fabricated device signify the development of the self-powered photodetector with broadband photodetection.
Growth Control of Cu2-xS Films for Visible-Near Infrared Photodetectors Karthickraja Ramakrishnan, Y. Ashok Kumar Reddy, B. Ajitha ACS Applied Electronic Materials, 2025 Nanostructured plasmonic copper sulfide (Cu2-xS), from the family of transition-metal sulfides with tunable optical and electrical properties, has drawn significant attention for broadband photodetectors in our research society. Herein, the attempt is made to grow Cu2-xS films via sulfurization of copper (Cu) films through the chemical vapor deposition (CVD) technique at different sulfurization temperatures (200–400 °C). A hexagonal structured CuS phase is observed for the film grown at 300 °C, with a higher crystalline nature confirmed through structural analysis. Surface compositional analysis suggests that the film deposited at 300 °C exhibits more copper vacancies, which shows the greater diffusion of sulfur atoms into copper films, which leads to the formation of well-aggregated nanospheres with larger grains over the film’s surface. Moreover, the band gap of the grown films is observed in the range of 1.79–1.92 eV, and the localized surface plasmon resonance (LSPR) band is observed in the near-infrared (NIR) region through optical studies, which confirms the plasmonic nature of Cu2-xS. Furthermore, the photodetector properties of the Au/Cu2-xS/Au test device are investigated in terms of photoresponsivity (Rλ), specific detectivity (D*), and external quantum efficiency (EQE) under visible and NIR light illuminations. The film grown at 300 °C exhibits superior results such as Rλ of 2.48 ± 0.02 A/W and 5.10 ± 0.02 A/W, D* of 3.02 ± 0.02 × 1012 Jones and 6.21 ± 0.02 × 1012 Jones, and EQE of 581 ± 5% and 646 ± 5% under visible (λ = 530 nm) and NIR (λ = 980 nm) light illuminations, respectively, with lower incident power density at a bias voltage of 3 V, which signify the potential of the fabricated test device in the broadband photodetectors.
Effect of Substrate Temperature on Cu-xO Growth for Enhanced Photodetector Performance in Visible Region Karthickraja Ramakrishnan, Y. Ashok Kumar Reddy, B. Ajitha IEEE Sensors Journal, 2024 The present study investigates the effect of substrate temperature (30 °C–300 °C) on the sputter-deposited Cu2-xO films for improved photodetector performance in the visible region. Cubic structured Cu2O phase is observed for all deposited films through structural analysis. Increasing substrate temperature causes the formation of nanospheres with higher grain size at 200 °C confirmed by the morphological images. Moreover, all the deposited thin films show a strong absorption band in the visible region (526–550 nm). Among deposited films, a lower bandgap (2.02 eV) is observed for the film deposited at 200 °C due to the higher surface area-to-volume ratio and increased grain size. The better crystalline nature, more copper vacancy, and formation of nanospheres with a larger grain size of the film deposited at 200 °C result in higher mobility and conductivity. Furthermore, the photodetector performance of the Au/Cu2-xO/Au test devices is studied under the visible light ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> = 530 nm) irradiation. Among samples, the sample grown at 200 °C showed higher photocurrent ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$36.10~\mu \text{A}$ </tex-math></inline-formula> ), <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {on}}/{I}_{\text {off}}$ </tex-math></inline-formula> ratio (183.50), photoresponsivity (1.127 A/W), specific detectivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${22.40} \times {10}^{{11}}$ </tex-math></inline-formula> Jones), and faster response times ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{r}$ </tex-math></inline-formula> = 92 ms and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau _{f}$ </tex-math></inline-formula> = 84 ms) even at lower incident optical power density (0.1283 mW/cm2). These improved experimental results signify the potential of the fabricated test device at 200 °C for the optoelectronics devices.
Evaluation of hydrogen gas-sensing performance based on polymorphic-engineered In2O3 nanostructures S Deb, A Mondal, B Ajitha, YAK Reddy Microchemical Journal, 115914 , 2025 2025 Citations: 2
Asymmetric Electrode-Driven Self-Powered Photodetector Using Cu 2-x S Film K Ramakrishnan, YAK Reddy, B Ajitha ACS Applied Electronic Materials 7 (19), 9146-9158 , 2025 2025 Citations: 2
Seed-mediated growth of gold nanorods for enhanced catalytic activity D Hema, B Ajitha Inorganic Chemistry Communications 179, 114882 , 2025 2025 Citations: 3
Self-Powered Photodetector Based on p (Cu 2 O)– n (MoO 3 ) Junction Architecture: Analyzing the Influence of Depletion Region Width on the Photodetector Properties A Mondal, K Ramakrishnan, S Deb, B Ajitha, YAK Reddy ACS Applied Energy Materials 8 (15), 11719-11731 , 2025 2025 Citations: 2
Growth Control of Cu 2-x S Films for Visible-Near Infrared Photodetectors K Ramakrishnan, YAK Reddy, B Ajitha ACS Applied Electronic Materials 7 (9), 4144-4160 , 2025 2025 Citations: 2
Development of room-temperature operable TiO2-x-based hydrogen gas sensor with light irradiation A Vijaykumar, A Mondal, S Deb, B Ajitha, YAK Reddy Applied Surface Science 670, 160664 , 2024 2024 Citations: 14
Effect of Substrate Temperature on Cu₂- x O Growth for Enhanced Photodetector Performance in Visible Region K Ramakrishnan, YAK Reddy, B Ajitha IEEE Sensors Journal 24 (8), 12296-12303 , 2024 2024 Citations: 4
High porosity and oxygen vacancy enriched WO3-x thin films for room temperature hydrogen gas sensors PVK Yadav, A Mondal, B Ajitha, J Jarugala, YAK Reddy International Journal of Hydrogen Energy 50, 878-888 , 2024 2024 Citations: 32
Effect of calcination temperature on NiO for hydrogen gas sensor performance SHS Pai, A Mondal, B Ajitha, YAK Reddy International Journal of Hydrogen Energy 50, 928-941 , 2024 2024 Citations: 83
Oxygen partial pressure dependent sputtered copper oxide films for visible photodetectors K Ramakrishnan, YAK Reddy, B Ajitha Surfaces and Interfaces 41, 103264 , 2023 2023 Citations: 15
Enhanced TCR results of TiOx thin films for uncooled infrared microbolometers YAK Reddy, PVK Yadav, TR Barathy, B Ajitha, I Yadav, S Gupta 2023 IEEE Applied Sensing Conference (APSCON), 1-3 , 2023 2023 Citations: 2
Review on metal sulfide-based nanostructures for photodetectors: From ultraviolet to infrared regions R Karthickraja, B Ajitha, YAK Reddy Sensors and Actuators A: Physical 349, 114051 , 2023 2023 Citations: 72
TiO2/CeO2 Core/Shell nanostructures for photocatalytic and photo electrochemical applications K Ramakrishnan, V Gayathri, K Aravinthkumar, K Ramachandran, B Ajitha, ... Inorganic Chemistry Communications 144, 109842 , 2022 2022 Citations: 34
Advancements of uncooled infrared microbolometer materials: A review PVK Yadav, I Yadav, B Ajitha, A Rajasekar, S Gupta, YAK Reddy Sensors and Actuators A: Physical 342, 113611 , 2022 2022 Citations: 155
Superior UV photodetector performance of TiO2 films using Nb doping PVK Yadav, B Ajitha, CMA Ahmed, YAK Reddy, VRM Reddy Journal of Physics and Chemistry of Solids 160, 110350 , 2022 2022 Citations: 60
Improved UV photodetector performance of NiO films by substitutional incorporation of Li PVK Yadav, B Ajitha, V Annapureddy, YAK Reddy, A Sreedhar Materials Letters 301, 130296 , 2021 2021 Citations: 25
Silver nanoparticle embedded polymethacrylic acid/polyvinylpyrrolidone nanofibers for catalytic application B Ajitha, CW Ahn, PVK Yadav, YAK Reddy Journal of Environmental Chemical Engineering 9 (5), 106291 , 2021 2021 Citations: 17
Recent advances in development of nanostructured photodetectors from ultraviolet to infrared region: A review PVK Yadav, B Ajitha, YAK Reddy, A Sreedhar Chemosphere 279, 130473 , 2021 2021 Citations: 173
Enhanced Performance of WO 3 Photodetectors Through Hybrid Graphene-Layer Integration PVK Yadav, B Ajitha, YA Kumar Reddy, VR Minnam Reddy ACS Applied Electronic Materials 3 (5), 2056-2066 , 2021 2021 Citations: 46
Effect of sputter pressure on UV photodetector performance of WO3 thin films PVK Yadav, B Ajitha, YAK Reddy, VRM Reddy, M Reddeppa, MD Kim Applied Surface Science 536, 147947 , 2021 2021 Citations: 94
MOST CITED SCHOLAR PUBLICATIONS
Green synthesis and characterization of silver nanoparticles using Lantana camara leaf extract B Ajitha, YAK Reddy, PS Reddy Materials Science and Engineering: C 49, 373-381 , 2015 2015 Citations: 461
Assisted green synthesis of copper nanoparticles using Syzygium aromaticum bud extract: Physical, optical and antimicrobial properties KM Rajesh, B Ajitha, YAK Reddy, Y Suneetha, PS Reddy Optik 154, 593-600 , 2018 2018 Citations: 322
Biogenic nano-scale silver particles by Tephrosia purpurea leaf extract and their inborn antimicrobial activity B Ajitha, YAK Reddy, PS Reddy Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 121, 164-172 , 2014 2014 Citations: 314
Role of capping agents in controlling silver nanoparticles size, antibacterial activity and potential application as optical hydrogen peroxide sensor B Ajitha, YAK Reddy, PS Reddy, HJ Jeon, CW Ahn RSC Advances 6 (42), 36171-36179 , 2016 2016 Citations: 280
Recent advances in development of nanostructured photodetectors from ultraviolet to infrared region: A review PVK Yadav, B Ajitha, YAK Reddy, A Sreedhar Chemosphere 279, 130473 , 2021 2021 Citations: 173
Biosynthesis of silver nanoparticles using Momordica charantia leaf broth: Evaluation of their innate antimicrobial and catalytic activities B Ajitha, YAK Reddy, PS Reddy Journal of Photochemistry and Photobiology B: Biology 146, 1-9 , 2015 2015 Citations: 160
Enhanced antimicrobial activity of silver nanoparticles with controlled particle size by pH variation B Ajitha, YAK Reddy, PS Reddy Powder Technology 269, 110-117 , 2015 2015 Citations: 158
Advancements of uncooled infrared microbolometer materials: A review PVK Yadav, I Yadav, B Ajitha, A Rajasekar, S Gupta, YAK Reddy Sensors and Actuators A: Physical 342, 113611 , 2022 2022 Citations: 155
Biosynthesis of silver nanoparticles using Plectranthus amboinicus leaf extract and its antimicrobial activity B Ajitha, YAK Reddy, PS Reddy Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 128, 257-262 , 2014 2014 Citations: 153
Synthesis of silver nanoparticles in an eco-friendly way using Phyllanthus amarus leaf extract: Antimicrobial and catalytic activity B Ajitha, YAK Reddy, HJ Jeon, CW Ahn Advanced Powder Technology 29 (1), 86-93 , 2018 2018 Citations: 123
Lantana camara leaf extract mediated silver nanoparticles: Antibacterial, green catalyst B Ajitha, YAK Reddy, S Shameer, KM Rajesh, Y Suneetha, PS Reddy Journal of Photochemistry and Photobiology B: Biology 149, 84-92 , 2015 2015 Citations: 122
Instant biosynthesis of silver nanoparticles using Lawsonia inermis leaf extract: Innate catalytic, antimicrobial and antioxidant activities B Ajitha, YAK Reddy, PS Reddy, Y Suneetha, HJ Jeon, CW Ahn Journal of Molecular Liquids 219, 474-481 , 2016 2016 Citations: 104
Synthesis of copper nanoparticles and role of pH on particle size control KM Rajesh, B Ajitha, YAK Reddy, Y Suneetha, PS Reddy Materials Today: Proceedings 3 (6), 1985-1991 , 2016 2016 Citations: 103
Effect of sputter pressure on UV photodetector performance of WO3 thin films PVK Yadav, B Ajitha, YAK Reddy, VRM Reddy, M Reddeppa, MD Kim Applied Surface Science 536, 147947 , 2021 2021 Citations: 94
Oxygen partial pressure dependent UV photodetector performance of WO3 sputtered thin films PVK Yadav, YAK Reddy, B Ajitha, VRM Reddy Journal of Alloys and Compounds 816, 152565 , 2020 2020 Citations: 93
Effect of calcination temperature on NiO for hydrogen gas sensor performance SHS Pai, A Mondal, B Ajitha, YAK Reddy International Journal of Hydrogen Energy 50, 928-941 , 2024 2024 Citations: 83
Biomimetic synthesis of silver nanoparticles using Syzygium aromaticum (clove) extract: Catalytic and antimicrobial effects B Ajitha, YAK Reddy, Y Lee, MJ Kim, CW Ahn Applied Organometallic Chemistry 33 (5), e4867 , 2019 2019 Citations: 77
Enhanced UV photodetector performance in bi-layer TiO2/WO3 sputtered films YAK Reddy, B Ajitha, A Sreedhar, E Varrla Applied Surface Science 494, 575-582 , 2019 2019 Citations: 75
Review on metal sulfide-based nanostructures for photodetectors: From ultraviolet to infrared regions R Karthickraja, B Ajitha, YAK Reddy Sensors and Actuators A: Physical 349, 114051 , 2023 2023 Citations: 72
Sesbania grandiflora leaf extract assisted green synthesis of silver nanoparticles: Antimicrobial activity B Ajitha, YAK Reddy, KM Rajesh, PS Reddy Materials Today: Proceedings 3 (6), 1977-1984 , 2016 2016 Citations: 62