Abstract
Organic thin-film transistors (OTFTs) in device physics is currently considered as a standout amongst the most progressive concepts of device applications. Currently, due to humongous technological progress, OTFT with high mobilities can be produced that are comparable to silicon technology. This remarkable mobility is considered as a benchmark for more demanding applications which is accomplished by novel, tenable organic semiconductor materials such as pentacene and the tailoring of their geometries and characteristics. In addition, pentacene demonstrates charge carrier mobilities up to 5.5 cm(2)/Vs. However very low mobility was achieved in OTFTs due to fabrication defects, material processing etc. The most important defect that arise during the fabrication process is contact interfaces in OTFTs, which highly effect the device performance. Thus, in this article, we will review the current progress of contact engineering of OTFTs with special emphasis on electrode/pentacene interfaces of pentacene-based organic thin film transistors. Further, this review aims to provide an in-depth understanding of bottlenecks to improve the OTFTs performance. After a short introduction, the historical background of pentacene-based OTFTs is discussed that focuses on different methods and materials employed so far to improve the contact between pentacene layer. Also, the review presents the key challenges in the geometry of pentacene based OTFT that is the direct deposition of metal electrodes onto the pentacene channel layer in top contact interface due to which poor carrier injection, high barrier height, chemical diffusion between both layers, high contact resistance and surface roughness has been observed which highly affects the device performance especially the field effect mobility. Also, the state-of-the-art devices and related models that widely employ pentacene are presented. This detailed review will assist the future researchers in understanding and improving field-effect properties of OTFTs.