Design optimized intermixed phase by tuning polymer-fullerene intercalation for free charge generation

The intermixed phase is important in effective charge separation due to the formation of cascaded energy landscape between intermixed phase and pure phases in polymerifullerene solar cells. However, the quantitative relationship between the charge separation and the content of intermixed phase has not been investigated clearly so far. Here, we proposed to tune the content of the polymer/PC71BM intermixed phase by changing the polymer solution conformation. Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) and PC71BM was selected as a model system. The organization of the PBT7T in solution promotes the formation of ordered aggregates as aging time increases, the interdigitation of side-chains restricts the intercalation of PC71BM. Therefore, the intermixed phase formed by intercalation PC71BM to PBTTT side chain can be controlled. When the aging time increasing from 0 to 80 min, the extent of intercalation gradually from almost complete intercalated phase to almost non-intercalated. As the content of intercalated phase is about 11%, the charge dissociation is most efficient and short circuit current (J(sc)) increased from 1.60 mA/cm(2) to 4.94 mA/cm(2), leading to optimized device performance. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.