Fig. 1. (a) Structural schematic diagram of perovskite solar cells using ZnO nanorods as ETL; (b) comparison of the electrical proper-ties of ZnO, TiO₂; (c) the energy level of ZnO, TiO₂, and other usually used materials in PSCs.

Fig. 2. Characterization of (a) XRD spectrum and (b) steady-state PE spectrum of ZnO nanorods growing at different water thermal temperatures.

Fig. 3. Positive SEM morphology of ZnO nanorods prepared from different seed crystal layers: (a) 3 layers; (b) 5 layers; (c) 7 layers

Fig. 4. SEM photograph of ZnO nanorods prepared on the ITO substrate using different concentrations of precursor fluids: (a) 0.01 mol/L; (b) 0.02 mol/L; (c) 0.03 mol/L; (d) PL spectrum.

Fig. 5. ZnO nanorods SEM morphology prepared on different substrates. (a) ITO; (b) AZO; (c) FTO.

Fig. 6. Changes of the length and diameter SEM of ZnO nanorods with water heat time: (a) 1.5 h; (b) 2.5 h; (c) 3.5 h; (d) 5.0 h; (e) 6.0 h; (f) 7.0 h; (g) 8.0 h; (h) 9.0 h; (i) 10.0 h; (j) line chart.

Fig. 7. (a) J-V curve of batteries with ZnO nanorods as ETL prepared at different hydrothermal times; (b) steady state PL spectrum and (c) absorption spectrum of perovskite on ZnO nanorods with different water heat time.

Fig. 8. Surface morphology of perovskite thin films growing on ZnO nanorods at different hydrothermal times SEM diagram: (a) 2.5 h; (b) 5.0 h; (c) 8.0 h.