Ambipolarity and Air Stability of Silicon Phthalocyanine Organic Thin‐Film Transistors

• Published in: Advanced electronic materials Vol. 5; no. 8
• Main Authors: Melville, Owen A., Grant, Trevor M., Mirka, Brendan, Boileau, Nicholas T., Park, Jeongwon, Lessard, Benoît H.
• Format: Journal Article
• Language: English
• Published: 01.08.2019
• Subjects: air versus vacuum; ambipolar; field effect transistor; organic thin‐film transistor; silicon phthalocyanines
• ISSN: 2199-160X; 2199-160X
• DOI: 10.1002/aelm.201900087

Silicon phthalocyanines (SiPcs) are a class of conjugated, planar molecule that have recently been investigated for use in organic photovoltaics (OPVs), organic light‐emitting diodes (OLEDs), and organic thin‐film transistors (OTFTs) due to their variable structure and ease of synthesis. Bottom‐gate, bottom‐contact OTFTs with four SiPc derivatives used as the semiconducting layers are prepared using physical vapor deposition. Devices using bis(pentafluorophenoxy) silicon phthalocyanine (F10‐SiPc) deposited on 140 °C substrates demonstrate electron field‐effect mobilities (μ) of up to 0.54 cm2 V−1 s−1, among the best currently reported for N‐type phthalocyanine‐based transistors. All materials show dramatic changes in charge transport when characterized under vacuum (P < 0.1 Pa) compared to in air at atmospheric pressure, typically switching from electron majority charge carriers to holes, with the change dependent on material structure and energetics. F10‐SiPc is close to balanced ambipolar in air, with μ around 5 × 10−3 cm2 V−1 s−1 for both holes and electrons. These results demonstrate SiPcs' potential as N‐type semiconductors in OTFTs as well as their adjustable charge transport as affected by operation environment. Silicon phthalocyanines (SiPcs) are a family of molecules that demonstrate N‐type or ambipolar behavior in organic thin‐film transistors (OTFTs), with electron field‐effect mobility up to 0.5 cm2 V−1 s−1. The extent of electron and hole transport in these OTFTs varies significantly with a change in axial (R) substituent and when characterized in air compared to vacuum.