Optimization of dye adsorption time and film thickness for efficient ZnO dye-sensitized solar cells with high at-rest stability

Table 2 Effects of dye adsorption time on electron transport properties of fabricated cells

Dye adsorption time (h)	R_k/R_w	Mean electron lifetime (ms)	Effective electron diffusion time (ms)	Charge collection efficiency (%)	Effective electron diffusion coefficient (×10⁻³ cm² s⁻¹)	Effective electron diffusion length (μm)
0.5	5.22	8.40	1.61	80.8	4.21	59.4
1	10.61	12.63	1.19	90.6	5.68	84.7
1.5	13.10	12.63	0.96	92.4	7.01	94.1
2	18.43	15.48	0.84	94.6	8.05	111.6
2.5	10.95	13.91	1.27	90.9	5.86	86.0
3	8.68	12.63	1.46	88.5	3.79	76.6

The thickness of the photoelectrode was 26 μm. R_k, charge transfer resistance at the ZnO/electrolyte interface; R_w, electron transport resistance in the ZnO network.