  We report an in-situ microbeam grazing incidence X-ray scattering study of
2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C$_8$-BTBT) organic
semiconductor thin film deposition by hollow pen writing. Multiple transient
phases are observed during the crystallization for substrate temperatures up to
$\approx$93$^\circ$C. The layered smectic liquid-crystalline phase of
C$_8$-BTBT initially forms and preceedes inter-layer ordering, followed by a
transient crystalline phase for temperature $>$60$^\circ$C, and ultimately the
stable phase. Based on these results, we demonstrate a method to produce
extremely large grain size and high carrier mobility during high-speed
processing. For high writing speed (25 mm/s) mobility up to 3.0 cm$^2$/V-s has
been observed.
