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Two Channels of Charge Generation in Perylene Monoimide Solid‐State Dye‐Sensitized Solar Cells
Author(s) -
Howard Ian A.,
Meister Michael,
Baumeier Björn,
Wonneberger Henrike,
Pschirer Neil,
Sens Rüdiger,
Bruder Ingmar,
Li Chen,
Müllen Klaus,
Andrienko Denis,
Laquai Frédéric
Publication year - 2014
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201300640
Subject(s) - materials science , ultrafast laser spectroscopy , photochemistry , dye sensitized solar cell , perylene , population , exciton , quenching (fluorescence) , spectroscopy , absorption (acoustics) , optoelectronics , fluorescence , electrode , chemistry , optics , physics , demography , quantum mechanics , sociology , electrolyte , composite material
The mechanism of charge generation in solid‐state dye‐sensitized solar cells using triarylamine‐substituted perylene monoimide dyes is studied by vis‐NIR broadband pump‐probe transient absorption spectroscopy. The experiments demonstrate that photoinduced electron injection into the TiO 2 can only occur in regions where Li + , from the commonly used Li‐TFSI additive salt, is present on the TiO 2 surface. Incomplete surface coverage by Li + means that some dye excitons cannot inject their electron into the TiO 2 . However it is observed in the solar cell structure that some of the dye excitons that cannot directly inject an electron still contribute to free charge generation by the previously hypothesized reductive quenching mechanism (hole transfer to the solid‐state hole transporter followed by electron injection from the dye anion into the TiO 2 ). The contribution of reductive quenching to the quantum efficiency of charge generation is significant, raising it from 68% to over 80%. Optimization of this reductive quenching pathway could be exploited to maintain high quantum efficiency in dyes with greater NIR absorption to achieve overall enhancements in device performance. It is demonstrated that broadband NIR transient spectroscopy is necessary to obtain population kinetics in these systems, as strong Stark effects distort the population kinetics in the visible region.