Suppressing crystallization in solution-processed thin films of organic semiconductors
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.