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Enhancing Long‐Term Device Stability Using Thin Film Blends of Small Molecule Semiconductors and Insulating Polymers to Trap Surface‐Induced Polymorphs
Author(s) -
Salzillo Tommaso,
Campos Antonio,
Babuji Adara,
Santiago Raul,
Bromley Stefan T.,
Ocal Carmen,
Barrena Esther,
Jouclas Rémy,
Ruzie Christian,
Schweicher Guillaume,
Geerts Yves H.,
MasTorrent Marta
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202006115
Subject(s) - materials science , thin film , polymer , semiconductor , metastability , chemical engineering , organic semiconductor , thermal stability , raman spectroscopy , polystyrene , nanotechnology , optoelectronics , composite material , organic chemistry , optics , chemistry , physics , engineering
The lack of long‐term stability in thin films of organic semiconductors can often be caused by the low structural stability of metastable phases that are frequently formed upon deposition on a substrate surface. Here, thin films of 2,7‐dioctyloxy[1]benzothieno[3,2‐ b ]benzothiophene (C 8 O‐BTBT‐OC 8 ) and blends of this material with polystyrene by solution shearing are fabricated. Both types of films exhibit the metastable surface‐induced herringbone phase (SIP) in all the tested coating conditions. The blended films reveal a higher device performance with a field‐effect mobility close to 1 cm 2 V −1 s −1 , a threshold voltage close to 0 V, and an on/off current ratio above 10 7 . In situ lattice phonon Raman microscopy is used to study the stability of the SIP polymorph. It is found that films based on only C 8 O‐BTBT‐OC 8 slowly evolve to the Bulk cofacial phase, significantly impacting device electrical performance. In contrast, the blended films stabilize the SIP phase, leading to devices that maintain a high performance over 1.5 years. This work demonstrates that blending small‐molecule organic semiconductors with insulating binding polymers can trap metastable polymorphs, which can lead to devices with both improved performance and long‐term stability.