Research area | Chemistry and Materials Science and Technology |
Title | Enhancing Long-Term Device Stability Using Thin Film Blends of Small Molecule Semiconductors and Insulating Polymers to Trap Surface-Induced Polymorphs |
Publication Type | Journal Article |
Publication year | 2020 |
Authors | Salzillo, T, Campos, A, Babuji, A, Santiago, R, Bromley, ST, Ocal, C, Barrena, E, Jouclas, R, Ruzie, C, Schweicher, G, Geerts, YH, Mas-Torrent, M |
Journal | ADVANCED FUNCTIONAL MATERIALS |
Type of Article | Article; Early Access |
Keywords | organic semiconductors, polymer blends, polymorphism}, {organic field-effect transistors |
Abstract | 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 (C8O-BTBT-OC8) 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 C8O-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. |
DOI | 10.1002/adfm.202006115 |