RESUMO
The fabrication of a superior-performance ultraviolet (UV) photodetector utilizing graphene quantum dots (GQDs) as a sensitization agent on a ZnO-nanorod/GaN-nanotower heterostructure has been realized. GQD sensitization displays substantial impact on the electrical as well as the optical performance of a heterojunction UV photodetector. The GQD sensitization stimulates charge carriers in both ZnO and GaN and allows energy band alignment, which is realized by a spontaneous time-correlated transient response. The fabricated device demonstrates an excellent responsivity of 3.2 × 103 A/W at -6 V and displays an enhancement of â¼265% compared to its bare counterpart. In addition, the fabricated heterostructure UV photodetector exhibits a very high external quantum efficiency of 1.2 × 106%, better switching speed, and signal detection capability as low as â¼50 fW.
RESUMO
A new self-activated green-yellow emitting Gd2CaZnO5 (GCZO) phosphor was synthesized using solid-state reaction method at high-temperature. XRD analysis confirmed the orthorhombic structure of the sample with the Pbnm space group. SEM micrographs reveal the irregular morphology with micron sized particles. Detailed photoluminescence (PL) analysis revealed that the excitation of the phosphor lies in the UV range (Ë377 nm) with the related broad green-yellow emission centered at 530 nm. The broad band emission ranging from Ë450 nm to 650 nm can be attributed to the surface defects and oxygen vacancies. The calculated luminescence decay lifetime for the optimized phosphor was found to be 2.925 µs. Furthermore, the color-coordinate (x, y) were calculated and found to be (0.44, 0.45), which lies in the green-yellow (Ë540 nm) region of the electromagnetic spectrum. The values of color coordinates and Color correlated temperature of 3289 K support the synthesized phosphor for the emission of warm white-light. These results perfectly established the suitability of this green-yellow emitting GCZO phosphor for Ultra-Violet Light-Emitting Diodes (LEDs) excited white-LED applications.
RESUMO
The Mn, Al co-doped ZnO samples were synthesized using solid-state reaction method and were annealed in furnace at 300 °C, 600 °C and 900°C temperature. All the samples prepared were investigated in detail for analysis of their structural, morphological, optical, magnetic and electrical behavior. The XRD data confirmed the hexagonal wurtzite structure of pristine, Mn doped and Al, Mn co-doped ZnO. For morphological investigation SEM and TEM techniques were employed. The PL properties of the ZnO:Mn, Al sample revealed emission in the blue region (415-438 nm). Furthermore, IV studies were carried out to examine the conductivity of the ZnO:Mn, Al samples and maximum conductivity was found in the sample with 5% Al doping and annealing temperature 600 °C. The magnetic measurements revealed room temperature ferromagnetic behavior in the optimized ZnO:Mn, Al sample annealed at 600 °C which indicates its suitability for Magneto-Opto Electronic Applications.
RESUMO
A new low-band gap dyad DPP-Ful, which consists of covalently linked dithiafulvalene-functionalized diketopyrrolopyrrole as donor and fullerene (C60 ) as the acceptor, has been designed and synthesized. Organic solar cells were successfully constructed using the DPP-Ful dyad as an active layer. This system has a record power-conversion efficiency (PCE) of 2.2 %, which is the highest value when compared to reported single-component organic solar cells.