We
explore both the synthesis of Cd-free blue quantum dots (QDs)
with high-quality photoluminescence (PL) characteristics and the fabrication
of high-efficiency QD light-emitting diodes (QLEDs). True blue (445
nm)-emissive, multishelled ZnSeTe QDs with a high PL quantum yield
of 84% and a sharp bandwidth of 27 nm are prepared. To obtain a better
electron transport layer (ETL) material, the surface of ZnMgO nanoparticles
(NPs) is modified by additional Mg reaction, leading to the possible
formation of a Mg(OH)2 layer on the surface-modified ZnMgO
(m-ZnMgO) NPs. The presence of a Mg(OH)2 overlayer, the
origin of the desirably reduced electron mobility, is supposedly responsible
for the improved charge balance of the QD emissive layer (EML). The
Mg(OH)2 layer is further found to alleviate the emission
quenching of the QD EML. Via combination of blue ZnSeTe QDs and m-ZnMgO
NP ETL, highly bright, efficient blue QLEDs with the record luminance
of 2904 cd/m2 and an external quantum efficiency of 9.5%
are demonstrated.
Indium phosphide (InP) has been regarded as the most promising composition of visible quantum dot (QD) emitters for the application to next-generation display devices primarily because of its environmental benignity. Bright, sharp emissivity of InP QDs should be pursued for the realization of high-efficiency, wide-color gamut display devices. Photoluminescence (PL) performance of InP QDs has been greatly improved based on synthetic advances enabling the securement of core size homogeneity and the formation of exquisite core/shell heterostructure. Until now, high-quality fluorescent InP QDs have been attainable exclusively through the use of a hazardous phosphorus (P) precursor of tris(trimethylsilyl)phosphine ((TMS) 3 P) against green chemistry. In this work, we report a synthetic breakthrough of green InP QDs toward narrow, bright emissivity by using a much cheaper, safer P alternative of tris(dimethylamino)phosphine ((DMA) 3 P). For this, QD synthesis proceeds via a so-called two-step approach, where as-grown InP cores are subjected to a stepwise size fractionation process and then placed in the consecutive double shelling of a composition-gradient ZnSe x S 1−x inner and a ZnS outer shell. The chemical composition (x) of the ZnSe x S 1−x inner shell in the range of 0.09−0.36 is varied to explore its effects on PL quantum yield (QY), size, and blue excitation light absorptivity. Because of the effective core size fractionation and elaborately designed heterostructure, the resulting InP/ZnSe x S 1−x /ZnS QDs exhibit exceptional green (527 nm) PL features of a sharp line width of 37 nm and a high PL QY of 87%, which have not been achievable to date from non-(TMS) 3 P-based QDs, when an optimal inner shell composition is applied.
In this paper differential kinematics was geometrically derived to be utilized in a calibration algorithm that improves the accuracy of the manipulation of a robot. Even though the mechanical components are manufactured and assembled precisely, small differences between the designed and the actual system always exist, due to both geometric and unmodelled errors. In order to resolve these problems, differential relationships between the model parameters and the end-effectorʹs posture were formulated. Subsequently, a derivative based estimation algorithm, such as an EKF (Extended Kalman Filter) manner, could be adopted to update the model parameters. The proposed algorithm includes joint flexibility, so is an advanced version of previous work, where a rigid joint model was adopted [1]. The effectiveness of the proposed algorithm was verified by a computer simulation with a 6 DOF manipulator robot.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.