Heterojunction Ambipolar Organic Transistors Fabricated by a Two-Step Vacuum-Deposition Process

Abstract

Ambipolar organic field‐effect transistors (OFETs) are produced, based on organic heterojunctions fabricated by a two‐step vacuum‐deposition process. Copper phthalocyanine (CuPc) deposited at a high temperature (250 °C) acts as the first (p‐type component) layer, and hexadecafluorophthalocyaninatocopper (F16CuPc) deposited at room temperature (25 °C) acts as the second (n‐type component) layer. A heterojunction with an interpenetrating network is obtained as the active layer for the OFETs. These heterojunction devices display significant ambipolar charge transport with symmetric electron and hole mobilities of the order of 10–4 cm2 V–1 s–1 in air. Conductive channels are at the interface between the F16CuPc and CuPc domains in the interpenetrating networks. Electrons are transported in the F16CuPc regions, and holes in the CuPc regions. The molecular arrangement in the heterojunction is well ordered, resulting in a balance of the two carrier densities responsible for the ambipolar electrical characteristics. The thin‐film morphology of the organic heterojunction with its interpenetrating network structure can be controlled well by the vacuum‐deposition process. The structure of interpenetrating networks is similar to that of the bulk heterojunction used in organic photovoltaic cells, therefore, it may be helpful in understanding the process of charge collection in organic photovoltaic cells.

Soft x-ray spectroscopy study of the element and orbital contributions to the electronic structure of copper hexadecafluoro-phthalocyanine

“…7 The incorporation of both n-type F 16 CuPc and p-type CuPc organic molecules within the active region of a transistor has been shown to be an efficient method for producing ambipolar organic field effective transistors. 8 Meanwhile, the use of nanometer-scale F 16 CuPc ribbons has been shown to produce high performance air-stable n-type transistors, due to the location of the organics' lowest unoccupied molecular orbital ͑LUMO͒ compared to the work functions of the Au and Ag contacts. 9 Naturally, CuPc/ F 16 CuPc and F 16 CuPc/metal heterojunctions have drawn attention in recent years, e.g., Refs.…”

Electronic Structure in Thin Film Organic Semiconductors

“…12 Aside from providing insight into the role of hydrogen in the observed proclivity towards p-type character of organic semiconductors, 13 F 16 CuPc is naturally advantageous from the perspective of future device applications, for example in organic field effective transistors. [14][15][16] As a result, there is a need for information regarding the bulk electronic properties of F 16 CuPc, as well as regrading interface electronic structure. Synchrotron radiation-excited photoemission spectroscopy and x-ray absorption spectroscopy (XAS) studies have previously been undertaken to investigate the energy alignment of acceptor-like CuPc and donor-like F 16 CuPc heterojunctions.…”

“…8 Of this family, there has been increased attention in recent years paid to CuPc and its derivatives F 16 CuPc and K-doped CuPc. 9,10 While CuPc semiconductor films are ptype in air, 11 F 16 CuPc is one of the few organic molecules exhibiting high performance and stability in air in n-type operation.…”

“…F 16 CuPc and CuPc: The fundamental properties 6 and technological applications 7 of metal phthalocyanines (M-Pc) have been the subject of much research, and indeed M-Pcs are one of the foremost planar organic molecular semiconductors used in many organic optoelectronic devices. 8 Of this family, there has been increased attention in recent years paid to CuPc and its derivatives F 16 CuPc and K-doped CuPc.…”

Integrating organic light-emitting diode and field-effect-transistor in a single device

“…Besides, organic field effect transistors (FETs) based on organic thin film or single crystals (such as tetracene, pentacene or rubrene) are also one of the topics that have attracted great attention in these years [4][5][6][7]. Furthermore, some research groups have reported field-effect transistor (FET) driven OLEDs and organic light-emitting transistors (OLETs) [8][9][10][11][12].…”