Organic single-crystal transistors: development of solution processes and charge transport mechanisms

Abstract

ABSTRACT Patternable solution-crystallized organic transistors are developed with high carrier mobility that exceeds 10 cm 2 /Vs. We have investigated techniques of crystallization during the fabrication of the organic semiconductor thin films from solution. Regulating direction of the crystal growth in the above process, we successfully formed crystalline films with the mobility as high as 10-12 cm 2 /Vs from newly developed air-stable organic semiconductor compounds of 2,7-dialkyl[1]benzothieno[3,2-b]benzothiophene (C n -BTBT) and 2,9-dialkyl-dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (C n -DNTT). Furthermore, comprehensive measurements of Hall-effect and temperature dependent mobility in the solution-crystallized single-crystal transistors tell us that thei r fundamental charge transport mechanism is band transport. Keywords: Organic Field-Effect Tran sistors, Single Crystal, Solution Process, Hall Effect 1. INTRODUCTION The development of organic thin-film transistors (TFTs) ha s been intensively driven by the fact that they can be fabricated by easy and potentially low-co st fabrication processes. Furthermore, near-room-temperature processes enable the semiconductor technologies to be realized on plastic substrates, raising expectation for post-silicon semiconductor industry. Solution-based processes such as drop-casting, spin-coating, and printing are the most desired methods for producing high-performance organic TFTs in this context. Regarding the performance of the solution-processed organic field-effect transistors, their switching speed is directly determined by charge carrier mobility in the organic semiconductors, which relies on microscopic electronic properties of molecule-to-molecule charge-transfer probability and the extent of molecular ordering. Therefore, it has been intensively challenging to create high-mobility active semiconductor layers using simple solution techniques. Various techniques have been reported that uses many different materials ranging from small molecules to polymers