@article{Hou:2024:10.1021/acs.chemmater.3c02353,
author = {Hou, X and Coker, JF and Yan, J and Shi, X and Azzouzi, M and Eisner, FD and McGettrick, JD and Tuladhar, SM and Abrahams, I and Frost, JM and Li, Z and Dennis, TJS and Nelson, J},
doi = {10.1021/acs.chemmater.3c02353},
journal = {Chemistry of Materials},
pages = {425--438},
title = {Structure–Property Relationships for the Electronic Applications of Bis-Adduct Isomers of Phenyl-C Butyric Acid Methyl Ester},
url = {http://dx.doi.org/10.1021/acs.chemmater.3c02353},
volume = {36},
year = {2024}
}

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TY  - JOUR
AB  - Higher adducts of a fullerene, such as the bis-adduct of PCBM (bis-PCBM), can be used to achieve shallower molecular orbital energy levels than, for example, PCBM or C60. Substituting the bis-adduct for the parent fullerene is useful to increase the open-circuit voltage of organic solar cells or achieve better energy alignment as electron transport layers in, for example, perovskite solar cells. However, bis-PCBM is usually synthesized as a mixture of structural isomers, which can lead to both energetic and morphological disorder, negatively affecting device performance. Here, we present a comprehensive study on the molecular properties of 19 pure bis-isomers of PCBM using a variety of characterization methods, including ultraviolet photoelectron spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, single crystal structure, and (time-dependent) density functional theory calculation. We find that the lowest unoccupied molecular orbital of such bis-isomers can be tuned to be up to 170 meV shallower than PCBM and up to 100 meV shallower than the mixture of unseparated isomers. The isolated bis-isomers also show an electron mobility in organic field-effect transistors of up to 4.5 × 10² cm²/(Vs), which is an order of magnitude higher than that of the mixture of bis-isomers. These properties enable the fabrication of the highest performing bis-PCBM organic solar cell to date, with the best device showing a power conversion efficiency of 7.2%. Interestingly, we find that the crystallinity of bis-isomers correlates negatively with electron mobility and organic solar cell device performance, which we relate to their molecular symmetry, with a lower symmetry leading to more amorphous bis-isomers, less energetic disorder, and higher dimensional electron transport. This work demonstrates the potential of side chain engineering for optimizing the performance of fullerene-based organic electronic devices.
AU  - Hou,X
AU  - Coker,JF
AU  - Yan,J
AU  - Shi,X
AU  - Azzouzi,M
AU  - Eisner,FD
AU  - McGettrick,JD
AU  - Tuladhar,SM
AU  - Abrahams,I
AU  - Frost,JM
AU  - Li,Z
AU  - Dennis,TJS
AU  - Nelson,J
DO  - 10.1021/acs.chemmater.3c02353
EP  - 438
PY  - 2024///
SN  - 0897-4756
SP  - 425
TI  - Structure–Property Relationships for the Electronic Applications of Bis-Adduct Isomers of Phenyl-C Butyric Acid Methyl Ester
T2  - Chemistry of Materials
UR  - http://dx.doi.org/10.1021/acs.chemmater.3c02353
UR  - https://www.webofscience.com/wos/woscc/full-record/WOS:001139446400001
VL  - 36
ER  - 

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