Effective doping of carbon nanotubes in phosphor and observation of bright electroluminescence by field enhanced hot electron injection

TL;DR

This study demonstrates that effective doping of shortened carbon nanotubes in ZnS:Cu phosphors enhances electroluminescent device brightness and efficiency through local field enhancement and hot electron injection, reducing operating voltage.

Contribution

It introduces a flux-assisted solid-state annealing method for doping CNTs into phosphors, significantly improving EL device performance via field enhancement and hot electron effects.

Findings

Shorter CNTs lead to greater local field enhancement and brightness.

Enhanced EL device efficiency without increased undesired current.

Hot electron injection improves energy transfer and device performance.

Abstract

Present work focuses on the effective doping of multi-walled carbon nanotube (CNT) in the ZnS:Cu phosphor system and thereafter improvement in the optical performance of electroluminescent (EL) device due to the effect of increased local field. To facilitate doping of CNTs into the phosphor and decrease the operating voltage of the EL device, CNTs were shortened by milling and incorporated effectively using a flux assisted solid-state annealing reaction. Interestingly shorter the length of CNTs used, greater was the local field enhancement, brightness and efficiency observed for the EL devices. When the field is applied, adequate charge carriers are tunneled into the ZnS:Cu system through the tips of the CNTs by forming high energy hot spots thus enhancing the local field. The improved device characteristics are due to field enhancement without flowing of undesired current in the EL device and effective transfer of energy from hot spots to copper activator causing field-ionization. The detailed electrical characterization of the novel EL device along with its brightness measurements are also presented by considering the hot electron injection model.