Antiambipolar, ambipolar, and unipolar charge transport in organic transistors based on a single vertical P–N heterointerface

Abstract

The charge-transport modes of organic heterojunction transistors (OHJTs) (unipolar, antiambipolar, and ambipolar) have great importance in determining their potential applications. Herein, we demonstrate OHJTs with tunable charge-transport modes based on a single vertical heterointerface consisting of p-type pentacene (bottom) and n-type F₁₆CuPc (top). Both unipolar and antiambipolar transport properties can be achieved based on the balance of the two charge carriers by adjusting the bottom layer thickness. A competition between electrons and holes to as the dominant carriers may appears that is attributed to the variation in the densities of two charge carriers. The operating mechanism and transport path are presented to elucidate the antiambipolar behavior in OHJT. To further detect the function of the heterointerface, an n-type/insulator/p-type structure is presented by inserting a high-κ organic dielectric layer (polyvinyl alcohol) to isolate the vertical heterointerface effects. Consequently, the devices exhibited a typical ambipolar transport, and simultaneously the antiambipolar peak in OHJT disappeared, which implies that the vertical p–n heterointerface effects play a crucial role in the antiambipolar phenomenon. Thus, the results manifest that the antiambipolar behavior could be achieved from a single vertical organic heterointerface. This study deepens the fundamental comprehension of charge transport behaviors in organic heterojunction devices.