Influence of Molecular Shape on Solid-State Packing in Disordered PC61BM and PC71BM Fullerenes.
Molecular and polymer packings in pure and mixed domains and at interfacial regions play an important role in the photoconversion processes occurring within bulk heterojunction organic solar cells (OSCs). Here, molecular dynamics simulations are used to investigate molecular packing in disordered (amorphous) phenyl-C70-butyric acid-methyl ester (PC71BM) and its C60 analogue (PC61BM), the two most widely used molecular-based electron-accepting materials in OSCs. The more ellipsoidal character of PC71BM leads to different molecular packings and phase transitions when compared to the more spherical PC61BM. Though electronic structure calculations indicate that the average intermolecular electronic couplings are comparable for the two systems, the electronic couplings as a function of orientation reveal important variations. Overall, this work highlights a series of intrinsic differences between PC71BM and PC61BM that should be considered for a detailed interpretation and modeling of the photoconversion process in OSCs where these materials are used.
Monika
M
Williams
Naga Rajesh
NR
Tummala
‡Department of Chemistry, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia.
Saadullah G
SG
Aziz
Chad
C
Risko
‡Department of Chemistry, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia.
Jean-Luc
JL
Brédas
amorphous solids; intermolecular electronic couplings; organic solar cells; substituted fullerenes