ABSTRACT
First- and second-generation solar cells are made with inorganic semiconductors using both bilayer junctions and tandem structures to efficiently collect free holes and electrons generated by the absorption of light. The third generation of solar cells includes organic photovoltaics (OPV), dye-sensitized cells (DSCs), perovskite solar cells (PSCs), and quantum dot (QD) cells that depart from the traditional p-n junction. Upon absorption of light in OPV cells, electrons are separated from holes and elevated to the lowest unoccupied energy level or molecular orbital (LUMO) before being transported out of the cell. DSCs use a photosensitive dye to absorb light energy, a semiconductor to transport excited electrons, and an electrolyte to replenish the transported electrons. PSCs are based on structures similar to the mineral perovskite and offer rapidly accelerating efficiencies and tunable bandgaps. And, QD cells use very small photosensitive particles to convert light to electrical energy over a high surface area with a bandgap (and color or spectral sensitivity) that is tunable. Many of these third-generation technologies offer flexible substrates and bendability that make them very attractive to wearable solar cell applications. This chapter provides an overview of these four major players within the third generation of solar cells.
