Or, if you want the professor's technical explanation, "dye sensitised solar cells with titanium oxide layers on a surface with light absorbing dyemolecules adsorbed on surface which can generate electricity".
The dyemolecules themselves are bound to tiny particles of titanium dioxide, a less-famous (but cheaper) semiconductor than silicon, and the whole assembly is immersed in an electrolyte and sandwiched between two electrodes.
In the case of dye-based cells, which were invented at the Federal Polytechnic School of Lausanne, in Switzerland, in the 1990s, the light is first captured by molecules of a photosensitive dye.
Each bead is doped with a mixture of chemicals that become electrically charged in response to odour molecules and that charge alters the colour of the dye.