ABSTRACT
This chapter provides an overview of the working principles of
photovoltaic cells and reviews them in terms of micro energy
harvesting.
Photovoltaic devices convert light into electric energy. There are
three fundamental processes needed to achieve this goal. The first
step is the absorption of a photon by which an electron is excited
from a lower state to a higher (less tightly bound) state. The
remaining unoccupied lower state from where the electron was
excited is called a hole. Next, the electron-hole pair has to be
spatially separated and finally the electron and the hole have to
be transported to and collected at their respective electrodes. In
the first step, i.e., the creation of an electron-hole pair through
the absorption of a photon, the energy of the photon is converted
into chemical energy as an electron-hole pair is uncharged.
Subsequently, the chemical energy is converted into electric energy
by separation of the charge carriers.
