Singlet Exciton Lifetimes in Conjugated Polymer Films for Organic Solar Cells
Type
ArticleAuthors
Dimitrov, Stoichko D.
Schroeder, Bob C.

Nielsen, Christian
Bronstein, Hugo

Fei, Zhuping
McCulloch, Iain

Heeney, Martin
Durrant, James R.

KAUST Department
Chemical Science ProgramKAUST Solar Center (KSC)
Physical Science and Engineering (PSE) Division
Date
2016-01-13Permanent link to this record
http://hdl.handle.net/10754/596174
Metadata
Show full item recordAbstract
The lifetime of singlet excitons in conjugated polymer films is a key factor taken into account during organic solar cell device optimization. It determines the singlet exciton diffusion lengths in polymer films and has a direct impact on the photocurrent generation by organic solar cell devices. However, very little is known about the material properties controlling the lifetimes of singlet excitons, with most of our knowledge originating from studies of small organic molecules. Herein, we provide a brief summary of the nature of the excited states in conjugated polymer films and then present an analysis of the singlet exciton lifetimes of 16 semiconducting polymers. The exciton lifetimes of seven of the studied polymers were measured using ultrafast transient absorption spectroscopy and compared to the lifetimes of seven of the most common photoactive polymers found in the literature. A plot of the logarithm of the rate of exciton decay vs. the polymer optical bandgap reveals a medium correlation between lifetime and bandgap, thus suggesting that the Energy Gap Law may be valid for these systems. This therefore suggests that small bandgap polymers can suffer from short exciton lifetimes, which may limit their performance in organic solar cell devices. In addition, the impact of film crystallinity on the exciton lifetime was assessed for a small bandgap diketopyrrolopyrrole co-polymer. It is observed that the increase of polymer film crystallinity leads to reduction in exciton lifetime and optical bandgap again in agreement with the Energy Gap Law.Citation
Singlet Exciton Lifetimes in Conjugated Polymer Films for Organic Solar Cells 2016, 8 (1):14 PolymersPublisher
MDPI AGJournal
PolymersAdditional Links
http://www.mdpi.com/2073-4360/8/1/14ae974a485f413a2113503eed53cd6c53
10.3390/polym8010014