4. Perovskite solar cell
4.1. Recent progress in efficient hybrid lead halide perovskite solar
cells
The DSSCs are promising low cost solar cells with merits of simple
and clean fabrication, low cost and abundant raw material, and offer
the possibilities to design solar cells with a large flexibility in shape,
color, and transparency. Integration into different products opens up
new commercial opportunities [100,129]. However, concern over
leakage of the liquid electrolyte has caused a bottleneck in rapid
development and commercialization; therefore, there is need for new
designs of solid-state sensitized solar cells to replace the liquid
electrolyte with hole-transporting material (HTM). Currently