Balancing the film strain of organic semiconductors for ultrastable organic transistors with a five-year lifetime

Abstract

The instability of organic field-effect transistors (OFETs) is one key obstacle to practical application and is closely related to the unstable aggregate state of organic semiconductors (OSCs). However, the underlying reason for this instability remains unclear, and no effective solution has been developed. Herein, we find that the intrinsic tensile and compressive strains that exist in OSC films are the key origins for aggregate state instability and device degradation. We further report a strain balance strategy to stabilize the aggregate state by regulating film thickness, which is based on the unique transition from tensile strain to compressive strain with increasing film thickness. Consequently, a strain-free and ultrastable OSC film is obtained by regulating the film thickness, with which an ultrastable OFET with a five-year lifetime is realized. This work provides a deeper understanding of and a solution to the instability of OFETs and sheds light on their industrialization.

Strain-Balanced Organic Semiconductor Film for Improving the Stability of Organic Field-Effect Transistors

“…To investigate the evolution of aggregate state and film strain in the OSC films, X-ray diffraction (XRD) measurements were systematically carried out. XRD is a typical strain analysis tool and is widely used in the characterization of film strain in the field of organic/inorganic semiconductors, , 2D materials, and perovskite materials. , When film strain (tensile strain or compressive strain) exists in materials, it can be compensated and/or balanced by the opposite strain, and a strain-balanced film can be obtained. ,, In OFETs, the charge transport zone is usually at a tensile strain state due to the stress induced by the substrate properties (Figure a), which is the deep origin of aggregate state instability and device failure. ,,, Regarding the OSC single crystals as the standard strain-free state, the lattice parameters of the strained OSC films are different from that of the OSC single crystals. Here, we defined the film strain as the relative change of the lattice distance ( d ) ε = d − d 0 d 0 where ε is the film strain of OSC films, and d and d 0 are the lattice distances of the strained OSC films and the OSC single crystal, respectively.…”

“…37,42,45 In OFETs, the charge transport zone is usually at a tensile strain state due to the stress induced by the substrate properties (Figure 1a), which is the deep origin of aggregate state instability and device failure. 26,30,32,33 Regarding the OSC single crystals as the standard strain-free state, the lattice parameters of the strained OSC films are different from that of the OSC single crystals. Here, we defined the film strain as the relative change of the lattice distance (d)…”

Advances in organic semiconductors for photocatalytic hydrogen evolution reaction

“…However, the energy of these excited states is usually high, leading to reactions with surrounding molecules that produce highly reactive species such as radicals and ions, which can easily cause oxidation and degradation of organic semiconductor materials. This can manifest as morphological changes and crystal phase transitions, a form of corrosion 134,135 . In contrast, inorganic semiconductors generally consist of a single element or a few elements, and their structures are relatively simple, resulting in lower corrosivity.…”

Early stage growth process of dinaphtho[2, 3-b:2', 3'-f]thieno[3, 2-b]thiophene (DNTT) thin film

“…The purpose of this research is to provide systematic knowledge on Dinaphtho [2, 3-b:2', 3'-f]thieno [3, 2-b]thiophenes (DNTTs) interfacial layers on SiO2 surfaces. DNTTs have been actively studied owing to their high carrier mobility over amorphous silicon and longterm atmospheric stabilities [1]. Recently, there have been interesting reports on the prediction of the initial structure at the insulating film surface [2], the initial layer instability [3], and the existence of a thin film phase [4] that differs from the bulk phase.…”

“…They emphasized that a more detailed study of the structure of the initial layers of the DNTT is needed. Chen et al have investigated that the main origin of the instability should be mainly caused by the strain effects in DNTT thin films [1], however, the discussion is not exhaustive and insight into the effect of thin film growth on initial layers configuration is required. These thin film growth processes have continued to be discussed in similar context schemes as the pentacene.…”