Silicon Phthalocyanines as Emerging n-Type Semiconductors in Thin Film Transistors

Abstract

Silicon phthalocyanines are emerging n-type semiconductors for use in organic photovoltaics (OPVs) and organic thin-film transistors (OTFTs).[1] Their low synthetic complexity paired with their versatile axial group facilitates the finetuning of their chemical properties, solution properties and processing characteristics without significantly affecting their frontier orbital levels or their absorption properties. The crystal engineering and film forming characteristics of silicon phthalocyanine semiconductors can be tuned through appropriate axial group functionalization, therefore facilitating their integration into OTFTs by solution processing or vapor deposition.We were the first to integrate SiPcs into OTFTs, and unlike the majority of phthalocyanines, SiPcs are inherently better electron transporting materials then hole transport materials. We demonstrated n-type mobilities on the order of 0.5 cm2/Vs which is among the best of all phthalocyanines.[3] Through axial functionalization we reported that changes in the electron withdrawing character of the axial group lead to predictable drops in device threshold voltage from 45 V to 5 V.[4] The axial group can also be used to improve the SiPc solubility leading to solution processable OTFTs where the choice of axial group also dictates the thin film morphology an ultimately the resulting device performance.[5] GIWAXS studies show that processing conditions and choice of axial groups leads to changes in molecular alignment at the interface providing critical insight into device optimization.This presentation will cover our recent advances in the development of structure property relationships between SiPc structure, thin film processing and resulting charge transport properties.REFERENCES1. ACS Applied Materials & Interfaces. 2021, 13, 31321-313302. Organic Electronics. 2020, 87, 1059763. Advanced Electronic Materials. 2019, 5, 19000874. ACS Appl. Electron. Mater. 2021, 3, 5, 2212–22235. ACS Applied Materials & Interfaces. 2020, 13, 1008-1020 Figure 1