In　this　work,　we　investigate　the　effect　of　phase　morphology　on　the　nature　of　charges　in　poly(2,5-bis(3tetradecyl-thiophen-2-yl)　thieno[3,2,-b]　thiophene)　(pBTTT-C-16)　and　phenyl-C-61-butyric　acid　methyl　ester　(PC61BM)　blends　over　timescales　greater　than　hundreds　of　microseconds　by　quasi-steady-state　photoinduced　absorption　spectroscopy.　Specifically,　we　compare　an　essentially　fully　intermixed,　one-phase　system　based　on　a　1　:　1　(by　weight)　pBTTT-C-16　:　PC61BM　blend,　known　to　form　a　co-crystal　structure,　with　a　two-phase　morphology　composed　of　relatively　material-pure　domains　of　the　neat　polymer　and　neat　fullerene.　The　co-crystal　occurs　at　a　composition　of　up　to　50　wt%　PC61BM,　because　pBTTT-C-16　is　capable　of　hosting　fullerene　derivatives　such　as　PC61BM　in　the　cavities　between　its　side　chains.　In　contrast,　the　predominantly　two-phase　system　can　be　obtained　by　manipulating　a　1　:　1　polymer　:　fullerene　blend　with　the　assistance　of　a　fatty　acid　methyl　ester　(dodecanoic　acid　methyl　ester,　Me12)　as　additive,　which　hinders　co-crystal　formation.　We　find　that　triplet　excitons　and　polarons　are　generated　in　both　phase　morphologies.　However,　polarons　are　generated　in　the　predominantly　two-phase　system　at　higher　photon　energy　than　for　the　structure　based　on　the　co-crystal　phase.　By　means　of　a　quasi-steady-state　solution　of　a　mesoscopic　rate　model,　we　demonstrate　that　the　steady-state　polaron　generation　efficiency　and　recombination　rates　are　higher　in　the　finely　intermixed,　one-phase　system　compared　to　the　predominantly　phase-pure,　two-phase　morphology.　We　suggest　that　the　polarons　generated　in　highly　intermixed　structures,　such　as　the　co-crystal　investigated　here,　are　localised　polarons　while　those　generated　in　the　phase-separated　polymer　and　fullerene　systems　are　delocalised　polarons.　We　expect　this　picture　to　apply　generally　to　other　organic-based　heterojunctions　of　complex　phase　morphologies　including　donor:　acceptor　systems　that　form,　for　instance,　molecularly　mixed　amorphous　solid　solutions,　underlining　the　generality　of　the　understanding　gained　here.