The Schottky energy barrier dependence of charge injection in organic light-emitting diodes

TLDR

The I–V characteristics of organic diodes are studied as a function of the Schottky energy barrier for charge injection from the contact. We present device model calculations of the I–V characteristics of organic diodes and compare them with measurements of MEH‑PPV structures. The structures are designed so that all current is injected from one contact, and the Schottky barrier is varied from essentially zero to over 1 eV by using different metal contacts. The model consistently describes the I–V behavior across the barrier range, showing space‑charge limited conduction for barriers below ~0.4 eV and contact‑limited conduction for larger barriers.

Abstract

We present device model calculations of the current–voltage (I–V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I–V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I–V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited.