Molecular Engineering for Enhanced Charge Transfer in Thin-Film Photoanode.

Citation data:

ACS applied materials & interfaces, ISSN: 1944-8252, Vol: 9, Issue: 40, Page: 34812-34820

Publication Year:
2017
Captures 2
Readers 2
Repository URL:
http://scholarworks.unist.ac.kr/handle/201301/22895
PMID:
28915010
DOI:
10.1021/acsami.7b08098
Author(s):
Kim, Jeong Soo; Kim, Byung-Man; Kim, Un-Young; Shin, HyeonOh; Nam, Jung Seung; Roh, Deok-Ho; Park, Jun-Hyeok; Kwon, Tae-Hyuk
Publisher(s):
American Chemical Society (ACS); AMER CHEMICAL SOC
Tags:
Materials Science; bonding effect; charge injection; intramolecular charge transfer; molecular engineering; self-aggregation
article description
We developed three types of dithieno[3,2-b;2',3'-d]thiophene (DTT)-based organic sensitizers for high-performance thin photoactive TiO films and investigated the simple but powerful molecular engineering of different types of bonding between the triarylamine electron donor and the conjugated DTT π-bridge by the introduction of single, double, and triple bonds. As a result, with only 1.3 μm transparent and 2.5-μm TiO scattering layers, the triple-bond sensitizer (T-DAHTDTT) shows the highest power conversion efficiency (η = 8.4%; V = 0.73 V, J = 15.4 mA·cm, and FF = 0.75) in an iodine electrolyte system under one solar illumination (AM 1.5, 1000 W·m), followed by the single-bond sensitizer (S-DAHTDTT) (η = 7.6%) and the double-bond sensitizer (D-DAHTDTT) (η = 6.4%). We suggest that the superior performance of T-DAHTDTT comes from enhanced intramolecular charge transfer (ICT) induced by the triple bond. Consequently, T-DAHTDTT exhibits the most active photoelectron injection and charge transport on a TiO film during operation, which leads to the highest photocurrent density among the systems studied. We analyzed these correlations mainly in terms of charge injection efficiency, level of photocharge storage, and charge-transport kinetics. This study suggests that the molecular engineering of a triple bond between the electron donor and the π-bridge of a sensitizer increases the performance of dye-sensitized solar cell (DSC) with a thin photoactive film by enhancing not only J through improved ICT but also V through the evenly distributed sensitizer surface coverage.