Zn2SnO4 based flexible PSCs: (a) TEM image (inset: high-resolution TEM image) and SAED pattern of ZSO NPs synthesized at 90 °C,
and plane view and cross-sectional SEM images of the fabricated ZSO thin film. (b) Transmittance and reflectance spectra of PEN/ITO/ZSO, PEN/
ITO/TiO2 and PEN/ITO substrate. (c) Cross-sectional SEM image and photograph of the ZSO-based flexible PSC (scale bar, 500 nm). (d) J−V
curve for the ZSO based flexible PSC measured by reverse scan with 10 mV voltage steps and 40 ms delay times under AM 1.5 G illumination. (a−d)
Reproduced with permission from ref 17. Copyright 2015 Nature Publishing Group
Device structure and key materials in each layer of a perovskite cell: (a) pillared PSC. (a) Reproduced with permission from ref 4.
Copyright 2013 Nature Publishing Group, (b) n−i−p and p−i−n cell architectures, and (c) schematic energy level diagram of perovskite materials with electron (n-type)/hole (p-type) transporting materials.