Supplementary information
Channeling of electron transport to improve collection efficiency in
mesoporous TiO2 dye sensitized solar cell stacks
Azhar Fakharuddin,a Irfan Ahmed,a Zulkeflee Khalidin,b Mashitah M. Yusoff,a Rajan Jose*a1
a
Nanostructured Renewable Energy Materials Laboratory, Faculty of Industrial Sciences &
Technology, Universiti Malaysia Pahang, 26300, Malaysia;
b
Faculty of Electrical and Electronics Engineering, Universiti Malaysia Pahang, 26300,
Malaysia.
* Author to whom correspondence should be addressed. Email: [email protected] or [email protected]. Nanostructured Renewable
Energy Materials Laboratory, Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang, 26300, Malaysia.
1
Supplementary information
Table SM 1: Analysis of current densities of few large area devices.
Type of
JSC
connection
mA/cm2
η (%)
Parallel (Grid
1
Reference
Ref. 1
12
5.5
10
5.1
Coated)
Parallel (Grid
2
Ref. 2
Coated)
Parallel (Grid
3
Ref. 3
11
5.8
15.1
7.4
~3
2.5
6.3
5.8
Coated)
Parallel (Grid
4
Ref. 4
Coated)
5
Series +
Ref. 5
parallel
6
Series +
Ref. 6
parallel
7
Z-type series
Ref. 7
9.7
3.53
~3
4.6
connection
8
Series
Ref. 8
connection
9
Monolithic
series
Ref. 9
~5
5**
connection
10
Single cell
21
11
Ref. 10
11
Single cell
20
>10
Ref. 11
12
Single cell
19
12.3
Ref. 12
* Values at 84 mW/cm2, ** Values calculated from graphs in article.
2
Supplementary information
Increment in current density
60
JSC increment (%)
(b)
51.78%
(a)
S-3
S1
40
S2
21.15 %
20
S-2
S3
0
S-1
S-1
S-3
S-2
Device
Figure SM1(a): A comparison of increment in current density of S2 and S3 with S1, (b) Working
electrodes of prototypes with total active similar for all the three devices.
3
Supplementary information
Electrochemical Impedance spectroscopy of the DSCs
For a porous thin layer, an infinite transmission line is used for circuit modeling but
for simplicity, the model is generalized for representative elements only. Figure S2 shows a
generalized model used for fitting the impedance data. This model corresponds to four
interfaces in a DSC (Figure S2) and various processes at those interfaces, i.e. (i) electron
transfer at FTO/semiconductor interface, (ii) electron transport and recombination at
semiconductor/electrolyte interface, (iii) diffusion of iodide/triodide ions in electrolyte, and
(iv) electron transfer at Pt/counter electrode interface. The impedance response of such a
system is represented as,13
1

 2
1
1
 R
2
2
 RT RREC 



i

T
Z 
coth
1


 R  

CT  
CT  

 1  i  

REC 

(2)
Here, RT is transport resistance, RREC is the recombination resistance from photoelectrode
to the electrolyte and ωCT is the recombination frequency at which recombination occurs. The
electrical equivalent of devices characterized by a high recombination resistance can be
represented as Figure S2.
Figure SM2: A simplified transmission line model used for fitting impedance data.
Here, RFTO/TiO2 is the FTO/semiconductor interface resistance, ZW1 is the Warburg
diffusion element related to diffusion of I3- inside TiO2 and ZW2 is diffusion element related to
I3- diffusion in the electrolyte.
4
Supplementary information
Reflectance (%)
100
80
60
40
20
0
400
600
(nm)
800
Figure SM3: Reflectance curves of the devices.
As the absorbance at 550 nm is ~90%, the values of α.d=1. 14,15
5
Supplementary information
Table SM 2: Calculated collection efficiency of devices equation 2 in manuscript.
Device
JSC (mA/cm2)
Thickness(µm)
Ln/L
ηc (%)
S1
10.93
14.1
1.08
84.05
S2
13.24
14.2
1.83
92.7
S3
16.6
14.1
3.96
98.3
6
Supplementary information
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