The high-efficiency and cost-effective materials and processes
for perovskite solar cells make them economically
viable for commercialization. Theoretically calculated maximum
efficiencies for perovskite solar cell are reported by
Yan et al. Based on considerations of the optical absorption
coefficient and thickness of the light absorber, the theoretical
maximum efficiency for a 1 μm-thick perovskite solar
cell composed of CH 3 NH 3 PbI 3 (phase with Pm3m symmetry)
is 26%, which is much higher than the efficiency of a GaAs
solar cell with the same thickness. This result indicates that
the perovskite solar cells are economically viable from a
viewpoint of efficiency. However, commercialization is still
challenging because of (1) the toxicity of Pb atoms, (2) longterm
stability, and (3) cost-effectiveness. So far, the champion
cells have been based on Pb-based perovskite materials.
However, the utilization of Pb-based materials has been
restricted due to their intrinsic toxicity. Future research directions
are going to be finding Pb-free light-absorbing materials.
Protection technology, in order not to release Pb from
the Pb-based perovskite solar cell device, will be important
issue, which may learn from the CdTe solar cell industry.