For photovoltaics, organic-inorganic perovskites are used, where the large cation A is
organic; often methylammonium (CH 3 NH
+ ) is used. X is a halogen, such as iodine
chlorine, or bromine, often in a mixed halide material. The cation B usually contains lead
(Pb). While tin (Sn) can also be used, which theoretically gives even more ideal bandgaps,
the stability is usually lower. When using these compounds (A: CH 3 NH
+
, B: Pb, X: I), the
total compound is called methylammonium lead triiodide and has the chemical formula
(CH 3 NH 3 PbI 3 ).
Figure 13.28 (b) shows the structure of a typical thin-film perovskite-based solar cell
[87]. A compact titanium dioxide (TiO 2 ) is deposited onto fluorine-doped tin oxide (FTO),
thus allowing electrons to be transported to the FTO layer. The perovskite layer is then
deposited onto this TiO 2 layer and covered by a hole-transporting material (HTM). On top
of the HTM, silver or gold is placed as a back metal. Besides thin-film architectures,
meso-porous architectures are also used, where the perovskite is present in a porous TiO 2
layer.
Perovskite materials used for solar cells have several properties that enable the high
efficiencies: they have a very strong absorption of the incident light combined with low
non-radiative carrier recombination. Further, their development can build on more than 20
years of experience from the development of organic and dye-sensitized solar cells [87].
All current high efficiency perovskite devices contain lead. This might be a problem
because Pb is toxic. However, as we have seen above, CdTe technology is currently very
successful, despite the toxic cadmium that is required to make these PV devices. Another
issue is degradation of the cells due to ultraviolet radiation and/or moisture. This
degradation can be quite fast [87] and is an issue that clearly must be solved if this
technology is to be applied industrially.
Measuring the J-V characteristics of perovskite cells needs to be done carefully,
because of hysteresis: depending on the voltage scan direction (from high to low or from
low to high voltages) and the scan speed, the shape of the measured J-V curve can change
significantly. This can lead to an overestimation or an underestimation of the device
performance [88].
organic; often methylammonium (CH 3 NH
+ ) is used. X is a halogen, such as iodine
chlorine, or bromine, often in a mixed halide material. The cation B usually contains lead
(Pb). While tin (Sn) can also be used, which theoretically gives even more ideal bandgaps,
the stability is usually lower. When using these compounds (A: CH 3 NH
+
, B: Pb, X: I), the
total compound is called methylammonium lead triiodide and has the chemical formula
(CH 3 NH 3 PbI 3 ).
Figure 13.28 (b) shows the structure of a typical thin-film perovskite-based solar cell
[87]. A compact titanium dioxide (TiO 2 ) is deposited onto fluorine-doped tin oxide (FTO),
thus allowing electrons to be transported to the FTO layer. The perovskite layer is then
deposited onto this TiO 2 layer and covered by a hole-transporting material (HTM). On top
of the HTM, silver or gold is placed as a back metal. Besides thin-film architectures,
meso-porous architectures are also used, where the perovskite is present in a porous TiO 2
layer.
Perovskite materials used for solar cells have several properties that enable the high
efficiencies: they have a very strong absorption of the incident light combined with low
non-radiative carrier recombination. Further, their development can build on more than 20
years of experience from the development of organic and dye-sensitized solar cells [87].
All current high efficiency perovskite devices contain lead. This might be a problem
because Pb is toxic. However, as we have seen above, CdTe technology is currently very
successful, despite the toxic cadmium that is required to make these PV devices. Another
issue is degradation of the cells due to ultraviolet radiation and/or moisture. This
degradation can be quite fast [87] and is an issue that clearly must be solved if this
technology is to be applied industrially.
Measuring the J-V characteristics of perovskite cells needs to be done carefully,
because of hysteresis: depending on the voltage scan direction (from high to low or from
low to high voltages) and the scan speed, the shape of the measured J-V curve can change
significantly. This can lead to an overestimation or an underestimation of the device
performance [88].