Effect of dye doping on the charge carrier balance in PPV light emitting diodes as measured by admittance spectroscopy

TL;DR

This study investigates how dye doping affects charge carrier mobilities and balance in PPV-based LEDs using admittance spectroscopy, revealing that dye doping significantly impacts electron mobility without altering hole mobility.

Contribution

It provides new insights into the influence of dye doping on charge transport and carrier balance in polymer LEDs through detailed admittance spectroscopy analysis.

Findings

Dye doping significantly reduces electron mobility.

Hole mobility remains unaffected by dye doping.

Capacitance minima serve as probes for electron trapping.

Abstract

Dye doping is a promising way to increase the spectral purity of polymer light-emitting diodes (LEDs). Here we analyze the frequency and field dependence of the complex admittance of Al-Ba-PPV-PEDOT-ITO LEDs with and without dye. We compare the charge carrier mobilities of pristine and dye-doped double-carrier and hole-only (Au replacing Al-Ba) devices. Dye doping is shown to significantly influence the electron mobilities while the hole mobilities are left unchanged and thereby changing the carrier balance in a double carrier device towards that of a hole only device. The minimum in the LED capacitance as function of voltage appears to be an excellent probe for the electron trapping phenomenon underlying the reduction of the mobility.