Supporting Information
Effect of shell thickness on small-molecule solar cells enhanced by dual
plasmonic gold-silica nanorods
Xiaoyan Xu, Qingguo Du, Bo Peng, Qihua Xiong, Lei Hong, Hilmi Volkan Demir,
Terence K. S. Wong,a) Aung Ko Ko Kyaw b) and Xiao Wei Sunc)
a)
Electronic mail: ekswong@ntu.edu.sg
Electronic mail: kyawakk@a-star.imre.edu.sg
c)
Electronic mail: EXWSun@ntu.edu.sg
b)
Synthesis of Au-silica nanorods
Au nanorods were synthesized by a seed-mediated method. The first step involves
the preparation of the Au seed solution by borohydride reduction of 0.6 ml of 0.01 M
NaBH4 in a mixture of 0.25 ml of 0.01 M HAuCl4 and 9.75 ml of 0.1 M aqueous
hexadecyltrimethylammonium bromide (CTAB) solution. The second step is the
synthesis of the Au nanorods. 40 µl of the Au seed solution was added to 200 ml of 0.1 M
CTAB, 2 ml of 0.01 M AgNO3, 10 ml of 0.01 M HAuCl4, 1.6 ml of 0.1 M ascorbic acid
and 4 ml of 1 M of HCl. After gently mixed inversion for 30 s, the reaction solution was
kept undisturbed for 16 hrs. Then, Au nanorods solution was centrifuged and re-dispersed
in 133.5 ml of deionized water.
Au-silica nanorods were obtained by the following procedure. First, the pH value of
2 mL of the Au nanorod solution was adjusted to around 10 by adding 0.1 M NaOH
solution. Then, silica shell with the thickness of 5 nm was formed on the surface of the
Au nanorod by the addition of 12 µl of a 20 vol% solution of tetraethyl orthosilicate
(TEOS) in methanol. Other shell thicknesses can be obtained by varying the amount of
TEOS. After stirring for 12 hrs, Au-silica nanorods were centrifuged and then redispersed in 3 ml ethanol. By adding 50 µl of hexadecyltrimethoxysilane and then stirring
for 18 hrs at 60 oC, hydrophobic core-shell nanostructures were obtained. Finally, Ausilica nanorods solution was centrifuged and then re-dispersed in CB.
FIG. S1. (a) HT spectra and (b) HR spectra for p-DTS(FBTTh2)2:PC70BM films with and
without 1 wt% Au-silica nanorods with silica shell thickness of 0 nm, 5 nm, 7 nm and 10
nm.