Abhinav Verma

An efficient white polymer light-emitting diode (WPLED) with stable Commission Internationale de l’éclairage (CIE) coordinates is fabricated. A blue electroluminescence (EL)-emitting conducting polymer [poly(9,9-di-n-hexyl-fluorenyl-2,7-diyl)] is used as a host for red [Bis(1-phenyl-isoquinoline)(acetylacetonate)iridium(III)] and green [iridium(III)tris(2-(4-tolyl)pyridinato-N,C2)] phosphorescent dyes. Although efficient triplet energy transfer is not possible in the green phosphorescent dye, the self-trapping mechanism is utilized for the emission of EL in the green region while an efficient triplet exciton energy transfer from the host to the red dye is utilized for EL in the red wavelength region. Concentrations of the three constituents are optimized to obtain pure white light of appropriate CIE coordinates. An efficient electron-blocking layer based on a biomaterial (salmon-DNA) is also incorporated in the WPLED to improve the device performance. The WPLED shows three distinguished peaks for the primary colors and achieved a maximum luminance and luminous efficiency of 350 cd/m2 and 0.86 cd/A, respectively.

The constitutive flow behavior of sintered cobalt in the temperature range 873 to 1473 K (600 to 1200 °C) and at strain rates from 0.001 to 10 s−1 has been studied using constant true strain rate hot compression tests. On the basis of these data, a processing map has been generated that depicts the variation of strain rate sensitivity with temperature and strain rate. The processing map reveals a domain of dynamic recrystallization (DRX) with an optimum condition of processing at 1273 K (1000 °C) and at 10−3 s−1. When deformed within the domain, the stress-strain curves exhibit a single peak followed by flow softening, leading to steady-state behavior. In addition to this, a recently developed approach based on flow curve analysis is used to study the DRX kinetics, which is found to follow an Avrami-type relation.