Suppressing crystallization in solution-processed thin films of organic semiconductors

Sherman, J. B., Chiu, C. Y., Fagenson, R., Wu, G., Hawker, C. J., Chabinyc, M. L.
MRS Communications

Glassy organic semiconductors provide a convenient host for dispersing guest molecules, such as dopants or light-emitting chromophores.

However, many glass-forming compounds will crystallize over time leading to changes in performance and stability in devices. Methods to

stabilize amorphous molecular solids are therefore desirable. We demonstrate that solution-processable glasses can be formed from a mixture

of 8,8′-biindeno[2,1-b]thiophenylene (BTP) atropisomers. While the trans isomer of methylated BTP, (E)-MeBTP crystallizes in spin-cast films,

the addition of (Z)-MeBTP slows the growth of the spherulites. X-ray scattering and optical microscopy indicate that films containing 40%

(Z)-MeBTP do not crystallize, even with the addition of nucleation agents and aging for several months.