Yang Sheng-Yi

Estimation of luminescence lifetime in frequency domain

Absorption is the origin of luminescence. But it must be noticed that the lifetime of luminescence might reversely influence the rate of absorption. In this paper, it is reported that the luminescence intensity of copper and manganese changes with the driving frequency at constant voltage. The variation of luminescent intensity depends only on the lifetime of luminescence but not on the type of quenching or other factors. Generally the rate of absorption is dominantly determined by the material property and the lifetime of luminescence centres, the absorption of shorter lifetime centre will be larger than that of the longer lifetime centre at the same excited condition.

To Improve the Efficiency of Bulk Heterojunction Organic Solar Cells by Incorporating CdSe/ZnS Quantum Dots

The efficiency of bulk heterojunction solar cells was enhanced by incorporating CdSe/ZnS core- shell colloidal quantum dots(CQDs) into copolymers of poly(3- hexylthiophene(P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester(PCBM) as the active layer,as result of the increased absorption in the visible region.The doping of CdSe/ZnS CQDs in the active layer and the influence of CQD surface ligands on device performance were investigated.A maximum power conversion efficiency(PCE) of 3.99% was obtained from the optimized solar cell ITO/PEDOT:PSS/P3HT:PCBM:(CdSe/ZnS)/Al(ITO:indium-tin oxide;PEDOT:poly(3,4-ethylendioxythiophene;PSS:poly(styrenesulfonate)) under AM1.5 illumination.This was45.1% improvement on the PCE of the control device ITO/PEDOT:PSS/P3HT:PCBM/Al.

Electroluminescence in organic single-layer light-emitting diodes at high fields

By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the central position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the central position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.