Liu, ZhenZhenLiuVanderspikken, JochenJochenVanderspikkenMantegazza, PaolaPaolaMantegazzaMoro, StefaniaStefaniaMoroHamid, MounaMounaHamidMertens, SigurdSigurdMertensVan den Brande, NikoNikoVan den BrandeLutsen, LaurenceLaurenceLutsenLemaur, VincentVincentLemaurBeljonne, DavidDavidBeljonneCostantini, GiovanniGiovanniCostantiniVandewal, KoenKoenVandewalVan Mele, BrunoBrunoVan MeleMaes, WouterWouterMaesGoderis, BartBartGoderis2024-10-092024-10-0920261616-301XWOS:001324457600001https://imec-publications.be/handle/20.500.12860/44614C14-alkoxy/alkyl PBTTT-OR-R, a derivative of the prototype PBTTT polymer, is relevant for optoelectronic applications because it combines PBTTT-like intercalation behavior with enhanced charge-transfer absorption at longer wavelengths. Additionally, fundamental insights are achieved by comparing this alternating conjugated polymer in the presence and absence of homocoupling defects. While the homocoupling-free oxidative variant, PBTTT-OR-R(O), as well as the Stille polymer with 19% homocoupling defects, PBTTT-OR-R(S), can both form co-crystals when stoichiometrically mixed with PC61BM, the co-crystal of the latter shows properties which are highly dependent on the thermal processing conditions because of the presence of these defects. The PBTTT-OR-R(S):PC61BM co-crystal shows a low thermal stability and PC61BM can progressively be expelled upon heating. In cooling from the melt and depending on the cooling rate, mixtures of PBTTT-OR-R(S) and PC61BM show a competition between co-crystallization (fast cooling) and separate crystallization (slow cooling). The PBTTT-OR-R(O):PC61BM co-crystal is much more stable up to at least 260 °C and is not influenced by the applied cooling rate. These findings also translate to the device level. The performance of PBTTT-OR-R:PC61BM photodiodes is severely deteriorated after isothermal annealing in case of PBTTT-OR-R(S), whereas the thermally robust co-crystals of PBTTT-OR-R(O) allow a more flexible design of optimized devices.Journal article10.1002/adfm.202413647WOS:001324457600001SEMICONDUCTING POLYMERSFULLERENESPACKING