2. Function description

The birth certificate of the first organic photovoltaic cell is often considered to be the publication by C.W. Tang who, in 1986, measured conversion efficiencies of the order of 1% with a bilayer made up of small molecules: copper phthalocyanine (CuPc) and a perylene tetracarboxylic derivative dibenzimidazole (PV after C.W. Tang's name, subsequently called PDI to avoid confusion). . The notion of heterojunction is already present, with CuPc playing the role of electron donor (D) versus PDI playing the role of electron acceptor (A). In practical terms, this means that the boundary energy levels of CuPc are closer to the vacuum level than those of PDI (it can also be said that CuPc has a lower...