“…In turn, the fourth generation cells are mostly organic groups, including polymers, chemically modified oxide graphene, nanotubes, TiO x or ZnO [ 206 , 207 ]. Work on the development of polymer photovoltaics, which was carried out in Wrocław (Poland), aimed at the construction and characteristics of photovoltaic cellular polymer cells, both on the substrate rigid as well as flexible, containing polymer rye of various chemical structure, fullerene derivatives (PCBM—[6,6]-phenyl-C 61 -butyric acid methyl ester, PC 71 BM—[6,6]-phenyl-C 71 -butyric acid methyl ester), as well as graphene oxide, nanotubes, TiO 2 , Ag, and liquid crystals [ 208 , 209 , 210 , 211 , 212 , 213 , 214 , 215 , 216 , 217 , 218 , 219 , 220 , 221 ]. Details of the mechanism of action and type of organic photovoltaic cells is discussed in the publication [ 206 , 222 ].…”