Yongning Zhou

Monte Carlo simulation of charge transport in electrically doped organic solids

A model to study the charge transport in electrically doped organic solids via Monte Carlo simulation is proposed. The model includes the finite rate of all possible electron transfers between host and dopant molecules. It is found that for efficiently doped materials, the conductivity increases with dopant concentration, first sublinearly and then superlinearly. The conductivity of electrically doped films is also dependent on the dopant–host energy-level offset: it is high when the ionization of dopants is energetically favourable, but decreases exponentially with increasing energy barrier for dopants to ionize.

Non-doped red emission: A solution for bias-independent red emission

The bias dependence of the emission color of organic light-emitting devices (OLEDs) was investigated. We fabricated four red emission devices with different structures. The general bias-dependent color shift of the emissions was characterized for the first three devices. The color shift can be explained by the presence of either two different recombination zones, or a doped layer composed of two emitting materials. By avoiding the structures that induce the color shift, a bias-independent red emitting device was fabricated.