▁as ▁phot ore cept ors ▁in ▁elect roph ot ography . ▁This ▁requires ▁films ▁have ▁a ▁thick ness ▁of ▁several ▁mic rom eters ▁that ▁can ▁be ▁prepared ▁using ▁the ▁doctor - bla de ▁technique . ▁ ▁M ole cular ▁cry st als ▁In ▁the ▁early ▁days ▁of ▁fundamental ▁research ▁into ▁organ ic ▁sem icon duct ors ▁the ▁pro tot yp ical ▁materials ▁were ▁free - standing ▁single ▁cry st als ▁of ▁the ▁ac ene ▁family , ▁e . g . ▁anth rac ene ▁and ▁t et rac ene . ▁The ▁advantage ▁of ▁employ ing ▁mole cular ▁cry st als ▁instead ▁of ▁am orph ous ▁film ▁is ▁that ▁their ▁charge ▁car rier ▁mob ilities ▁are ▁much ▁larger . ▁This ▁is ▁of ▁particular ▁advantage ▁for ▁OF ET ▁applications . ▁Ex amples ▁are ▁thin ▁films ▁of ▁cry st all ine ▁rub rene ▁prepared ▁by ▁hot ▁wall ▁ep it axy . ▁ ▁Ne at ▁polym er ▁films ▁They ▁are ▁usually ▁processed ▁from ▁solution ▁employ ing ▁variable ▁de position ▁techniques ▁including ▁simple ▁spin - co ating , ▁in k - jet ▁de position ▁or ▁industrial ▁re el - to - re el ▁co ating ▁which ▁allows ▁prepar ing ▁thin ▁films ▁on ▁a ▁flexible ▁substr ate . ▁The ▁materials ▁of ▁choice ▁are ▁conjug ated ▁polym ers ▁such ▁as ▁poly - th i oph ene , ▁poly - phen yl ene vin yl ene , ▁and ▁cop ol ym ers ▁of ▁altern ating ▁don or ▁and ▁accept or ▁units ▁such ▁as ▁members ▁of ▁the ▁poly ( car baz ole -