Effect of shallow traps on polaron transport at the surface of organic semiconductors

TL;DR

This study investigates how shallow traps influence polaron transport at the surface of organic semiconductors, revealing their impact on mobility and trapping times in single-crystal tetracene devices.

Contribution

It provides the first measurement of the dependence of polaron mobility on shallow trap density and estimates key trapping parameters in organic semiconductors.

Findings

Shallow traps decrease polaron mobility at the surface.

Average polaron trapping time is approximately 50 ps.

Shallow trap density is estimated at 3 x 10^11 cm^-2.

Abstract

The photo-induced electron and hole transfer across the semiconductor-dielectric interface in trap dominated p-type organic field-effect transistors (OFETs) has been investigated. It has been observed that the transfer of electrons into the dielectric results in a decrease of the field-effect mobility of polarons, suggesting that additional shallow traps are generated in the conduction channel. Using this effect, the dependence of the field-effect mobility on the density of shallow traps, mu(N), has been measured, which allowed to estimate the average polaron trapping time, tau_tr = 50 +- 10 ps, and the density of shallow traps, N_0 = (3 +- 0.5)*10^11 cm^-2, in the channel of single-crystal tetracene devices.