Page 181 - Multifunctional Photocatalytic Materials for Energy

Metal-based semiconductor nanomaterials for thin-film solar cells 167

Fig. 8.11 A typical flexible PSC based on TiO 2 ETM: (A) cross-sectional SEM image of the
inorganic-organic halide flexible planar heterojunction PSC and its corresponding schematic of the
flexible device structure, (B) digital image of a flexible PSC with a bending state, and (C) J-V curve
2
for the corresponding PSC device measured under simulated solar light (100 mW/cm AM 1.5G).
Reprinted with permission from B.J. Kim et al., Highly efficient and bending durable perovskite
solar cells: toward a wearable power source. Energy Environ. Sci. 8 (2015) 916–921.

Li et al. used mesoporous SnO 2 NP films to replace traditional mesoporous TiO 2 films
as ETMs and scaffold layers for mesoporous PSCs. After optimizing via TiCl 4 treat-
ment, they found that the device based on SnO 2 films achieved a PCE of >10% [52].
Dong and colleagues further investigated mesoscopic PSCs based on a SnO 2 compact
ETM layer and found that, in comparison with devices based on TiO 2 thin layers,
the SnO 2 -ETM-based PSCs exhibited higher J sc , V oc , fill factor, and PCE. Moreover,
the results revealed that the photovoltaic performance of SnO 2 -ETM-based PSCs was
highly dependent on the method of measurement [53]. Song et al. demonstrated that
SnO 2 films fabricated by a traditional spin-coating method can act as an electron-
selective contact for CH 3 NH 3 PbI 3 -based planar-heterojunction PSCs, yielding a high
PCE of 13.0%. Mechanical robustness tests showed that the cells were highly durable
with exposure to an ambient air environment for 30 days (as shown in Fig. 8.12) [54].
In addition, a low-temperature, solution-processed method was demonstrated by
Weijun Ke et al. to fabricate nanocrystalline SnO 2 film, which is an excellent alter-
native ETM material to replace TiO 2. In the application in PSCs, an average PCE of
16.02% measured from both reverse and forward voltage scans was obtained [55],