Marked alkyl- vs alkenyl-substitutent effects on squaraine dye solid-state structure, carrier mobility, and bulk-heterojunction solar cell efficiency.
We report two new squaraine dyes substituted at the pyrrolic rings with n-hexyl (squaraine 1) or n-hexenyl (squaraine 2) chains. Although internal molecular structure variations are minimal, the presence of the terminal double bond results in a much more compact solid-state structure, dramatically affecting charge transport in the thin films; the hole mobility of 2 is approximately 5x that of 1, and the BHJ OPV power conversion efficiency (PCE) of 2 is approximately 2x that of 1. PCEs surpassing 2% for ambient solution-processed devices are demonstrated, the largest so far achieved for squaraine-based organic solar cells.
Bagnis
Diego
D
Department of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, Illinois 60208, USA.
Beverina
Luca
L
Huang
Hui
H
Silvestri
Fabio
F
Yao
Yan
Y
Yan
Henry
H
Pagani
Giorgio A
GA
Marks
Tobin J
TJ
Facchetti
Antonio
A