Quantum Dot-Sensitized Solar Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 121

Fig. 23 TEM micrographs of (a) wide view of (CH 3 NH 3 )PbI 3 deposited TiO 2 (b) magnified
image of (CH 3 NH 3 )PbI 3 deposited TiO 2 . (Reprinted permission with Im et al. [ 172 ])
Fig. 24 Solid-state device and its cross-sectional mesostructure. a Real solid-state device.
b Cross-sectional structure of the device. c Cross-sectional SEM image of the device. d Active
layer-underlayer-FTO interfacial junction structure (Reprinted permission with Kim et al. [ 170 ])
deposited by spin-coating but the formulation of the perovskite incorporates a
halogens mixture (CH 3 NH 3 )PbI 2 Cl, and the scaffold material is Al 2 O 3 reached
PCE profiles of 10.9 % [ 174 ]. The perovskite is not able to inject electrons in the
Al 2 O 3 -mesostructured scaffold but the HTM layer, the spiro-MeOTAD, compen-
sates the situation injecting and transporting holes efficiently to the cathode. Etgar
et al. went one step further publishing a work where the HTM layer of the cell is
removed and the efficiency of the cell remains above 5 % using TiO 2 as scaffold
for the perovskite [ 175 ]. The two last discoveries raise the question if these cells
should be considered classic sensitized dye cells. But the last works published in
such devices to early and mid-2013, are more focus in increasing the cell efficiency
that in attempting to elucidate the mechanisms of storage, transportation and
injection of electrons and holes. High efficiency has been also obtained by using
polymeric HTM, [ 176 ] different morphologies of mesostructured layer, [ 177 ]
perovskites with a mixture of halogens, [ 178 , 179 ] and an impressive manufac-
turing technique employing sintering temperatures below 150 C and efficiencies