404
N. Kumari et al.
Table 3 Independent variable and levels used for response surface design
Independent variables
Symbols
Low level (−1)
Medium level (0)
High level (+1)
PbI 2 :MAI ratio
X 1
1:2
1:3
1:4
Rotational speed (rpm) X 2
2000
2500
3000
Annealing temperature
(°C)
X 3
60
80
100
Table 4 Experimental data for three-level, three-factor surface response design with coded values
of variables
Experimental run
Factors
Response
X 1 (ratio)
X 2 (rpm)
X 3 (°C)
Y (%)
1
2
2500
100
7.39
2
2
2500
60
5.41
3
3
2000
100
7.41
4
2
2000
80
5.29
5
4
2500
60
4.19
6
3
2000
60
5.59
7
3
3000
60
4.89
8
3
2500
80
7.37
9
4
3000
80
3.69
10
3
2500
80
7.34
11
4
2000
80
4.29
12
3
2500
80
7.31
13
4
2500
100
6.39
14
2
3000
80
4.71
15
3
2500
80
7.36
16
3
3000
100
7.09
17
3
2500
80
7.32
Y: Power conversion efficiency (%) of PSC
reference to in our past investigation (Kumari et al. 2019). What’s more, the fitted
outcomes are appeared in Table 5. From Table 5, plainly the p-estimation of the
quadratic model is under 0.0001. In this way, a quadratic model was considered for
further investigation.