Improvements in Stability and Performance of N,N′-Dialkyl Perylene Diimide-Based n-Type Thin-Film Transistors
✍ Scribed by Yugeng Wen; Yunqi Liu; Chong-an Di; Ying Wang; Xiangnan Sun; Yunlong Guo; Jian Zheng; Weiping Wu; Shanghui Ye; Gui Yu
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 309 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0935-9648
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✦ Synopsis
Low-temperature processable organic semiconductors offer intriguing prospects for inexpensive, flexible, large-area applications, such as displays, radio-frequency identification tags, circuits, and sensors. For organic thin-film transistor (OTFT) applications, n-type organic semiconductors with performance comparable to p-type materials, such as pentacene, are of great importance to realize the benefits of complementary circuit design. Perylene and naphthalene diimides and their derivatives are well-known n-type organic semiconductors due to their robust nature, flexible molecular-orbital energetics, and excellent charge-transport properties that can be tailorable via judicious functionalization. However, although perylene diimides exhibit outstanding mobilities greater than 0.6 cm 2 Á V À1 Á s À1 , the OTFTs only work in vacuum or under an inert atmosphere. One strategy to obtain air-stable n-type semiconductors is to incorporate strong electron-withdrawing groups, such as -CN, -C n F 2nþ1 , and -F; however, obtaining these materials commonly involves complicated synthetic processes.
Here, we increased the stability and performance for N,N 0 -dioctyl perylene diimide (PDI-C8) and N,N 0 -ditridecyl perylene diimide (PDI-C13) thin-film transistors using optimized growth rates and sulfur-modified electrodes. Chesterfield et al. demonstrated that high mobility for N-alkyl perylene diimide TFTs can be obtained by paying careful attention to film-growth conditions, but they did not discuss the effect of film growth rate on stability. Thiol-modified Au bottom-contact electrodes can also improve the device performance by decreasing the effective work function of the gold and the contact resistance. Although sulfur was once used as a reagent for modifying bottom-contact gold electrode in TFTs, the improvement in device performance was very small. We use sulfur to modify Au top-contact electrodes and remarkably increase the performance of OTFTs.