TY  - JOUR
A1  - Wade, Jessica
A1  - Wood, Sebastian
A1  - Collado-Fregoso, Elisa
A1  - Heeney, Martin
A1  - Durrant, James
A1  - Kim, Ji-Seon
T1  - Impact of Fullerene Intercalation on Structural and Thermal Properties of Organic Photovoltaic Blends
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - The performance of organic photovoltaic blend devices is critically dependent on the polymer:fullerene interface. These interfaces are expected to impact the structural and thermal properties of the polymer with regards to the conjugated backbone planarity and transition temperatures during annealing/cooling processes. Here, we report the impact of fullerene intercalation on structural and thermal properties of poly(2,5-bis(3-tetradecylthiophen-2-yOthieno[3,2-b]thiophene (PBTTT), a highly stable material known to exhibit liquid crystalline behavior. We undertake a detailed systematic study of the extent of intercalation in the PBTTT:fullerene blend, considering the use of four different fullerene derivatives and also varying the loading ratios. Resonant Raman spectroscopy allows morphology in situ during controlled heating and cooling. We find that small fullerene molecules readily intercalate into PBTTT crystallites, resulting in a planarization of the polymer backbone, but high fullerene loading ratios or larger fullerenes result in nonintercalated domains. During cooling from melt, nonintercalated blend films are found to return to their original morphology and reproduce all thermal transitions on cooling with minimal hysteresis. Intercalated blend films show significant hysteresis on cooling due to the crystallized fullerene attempting to reintercalate. The strongest hysteresis is for intercalated blend films with excess fullerene loading ratio, which form a distinct nanoribbon morphology and exhibit a reduced geminate recombination rate. These results reveal that careful consideration should be taken during device fabrication, as postdeposition thermal treatments significantly impact the charge generation and recombination dynamics.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.jpcc.7b05893
SN  - 1932-7447
VL  - 121
SP  - 20976
EP  - 20985
PB  - American Chemical Society
CY  - Washington
ER  -