Why molecular cells?
There is a need for low-cost efficient photovoltaics.
The single crystalline Si solar cells are efficient, but expensive and have energy payback time of ~7 years.
The thin film technologies (poly-Si, CdTe, CIGS) means lower cost and an energy payback in 1-1,5 years. Mounting and installation adds another 1-4 years. Current thin film technologies involves high investment costs.
Alternative PV technologies are dye solar cells: polymer heterojunction solar cells and dye-sensitized nanostructured solar cells in specific.