Impact of Thermal Annealing on the Dissolution of Semiconducting Polymer Thin Films

• Published in: Advanced electronic materials Vol. 10; no. 7
• Main Authors: Bai, Shaoling, Haase, Katherina, Perez Andrade, Jonathan, Hambsch, Mike, Talnack, Felix, Millek, Vojtech, Prasoon, Anupam, Liu, Jinxin, Arnhold, Kerstin, Boye, Susanne, Feng, Xinliang, Mannsfeld, Stefan C. B.
• Format: Journal Article
• Language: English
• Published: Wiley-VCH 01.07.2024
• Subjects: multi‐layer deposition; OFETs, polymer semiconductor; sequential solution process; thermal annealing; thermal cross‐linking
• ISSN: 2199-160X; 2199-160X
• DOI: 10.1002/aelm.202300801

Here, the effect of thermal annealing (TA) on the stability of solution‐sheared thin films of the semiconducting polymer poly[2,5‐bis(2‐octyldodecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione‐3,6‐diyl)‐alt‐(2,2′;5′,2′’;5′’,2′’’‐quaterthiophen‐5,5′’’‐diyl)] (PDPP4T) against the original coating solvent is studied, and it is shown that TA significantly improves the solvent resistance of semiconducting polymer films. Specifically, after the thin films are annealed at or above a critical temperature, the thin film thickness is largely retained when exposed to the original solvent, while for lower annealing temperatures material loss occurs, i.e., the thin film thickness is reduced due to rapid dissolution. The results of various techniques including grazing‐incidence wide‐angle x‐ray scattering (GIWAXS), atomic force microscopy (AFM), and ultraviolet‐visible‐near infrared (UV–vis‐NIR) absorption spectroscopy suggest physical changes as the cause for the increased solvent resistance. Such annealed films also show stable electrical characteristics in bottom‐gate, top‐contact (BGTC) organic field‐effect transistors (OFETs) even after solvent exposure. In initial tests, a multitude of technologically relevant polymers show such behavior, underlining the potential impact of such temperature treatments for the fabrication of multi‐layer polymer devices. This study demonstrates that post‐coating annealing changes the solvent resistance of semiconducting polymer layers and thus enables subsequent solution‐coating steps from non‐orthogonal solvents. The analysis of this phenomenon with a multitude of experimental techniques suggests morphological changes as the most plausible cause for the increased solvent resistance. Importantly, such an enhancement in solvent resistance is found for various semiconducting polymers.