SCHEDULED MAINTENANCE
Impact of highly crystalline, isoindigo-based small-molecular additives for enhancing the performance of all-polymer solar cells†
a
Gibok
Han,
a
Robert
Younts,
b
Wonho
Lee,
a
Bhoj R.
Gautam,
c
Seungjin
Lee,
a
Changyeon
Lee,
a
Taesu
Kim,
a
Felix Sunjoo
Kim,
d
Kenan
Gundogdu
b
and
Bumjoon J.
Kim
*a
Abstract
We have developed a simple yet versatile approach for enhancing the performance of all-polymer solar cells (all-PSCs) using a highly crystalline small-molecular additive, 6,6′-dithiopheneisoindigo (DTI). The DTI additive in a blend of PTB7-Th donor and P(NDI2HD-T) acceptor enhances the power conversion efficiency of all-PSCs from 5.9 to 6.8%. Based on the analyses of the electrical, optical, and structural properties of all-PSCs, it is suggested that DTI additives promote tighter π–π packing and larger sizes of crystalline domains. Such morphological changes of the PTB7-Th:P(NDI2HD-T) blend films upon the addition of DTI enhance the exciton lifetime and diffusion length, which are proved by static and femtosecond-transient absorption spectroscopies and time-resolved photoluminescence. As a result of improved exciton dissociation probability and charge transport, the short-circuit current density of all-PSCs is greatly increased. Importantly, we also show that the DTI additive can be applied to other all-PSC systems with different polymer donors and naphthalene diimide (NDI)-based polymer acceptors, where the efficiencies of all-PSCs are enhanced by 10–20%.
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