Crystallization　or　pi-stacked　aggregation　of　small　molecules　is　an　extensively　observed　phenomenon　which　favors　charge　transport　along　the　crystal　axis　and　is　important　for　the　design　of　organic　optoelectronic　devices.　Such　a　process　has　been　reported　for　N,N　＇-Bis(1-ethylpropyl)-3,4,9,10-perylenebis(dicarboximide)　(EPPTC).　However,　the　pi-stacking　mechanism　requires　solution-air　or　solution-solid　interfaces.　The　crystallization　or　aggregation　of　molecules　doped　in　solid　films　is　generally　thought　to　be　impossible,　since　the　solid　environment　surrounding　the　small　molecules　does　not　allow　them　to　aggregate　together　into　pi-stacked　crystals.　In　this　work,　we　demonstrate　that　the　movement　of　the　EPPTC　molecules　becomes　possible　in　a　solid　polymer　film　when　it　is　heated　to　above　the　glass　transition　temperature　of　the　polymer.　Thus,　crystal　particles　can　be　produced　as　a　doped　matrix　in　a　thin　solid　film.　The　crystallization　process　is　found　to　be　strongly　dependent　on　the　annealing　temperature　and　the　annealing　time.　Both　the　microscopic　and　spectroscopic　evaluations　verify　such　discoveries　and　characterize　the　related　properties　of　these　crystals.