Organic pn homojunction solar cell

Formation of pn homojunction in a single semiconductor material through doping is key for photocurrent generation in inorganic solar cells (SCs). In contrast, a donor/acceptor heterojunction is generally utilized in organic SCs in order to split coulombically bound exciton forming in organic semiconductors. Here, an organic pn homojunction SC showing high internal quantum efficiency of about 30% is reported. pn Homojunction was created by co-deposition of p or n type dopants and an organic semiconductor. An increase of the photocurrent density by more than 8 times, from the undoped device to pn homojunction device with 5% doping, was observed. The increase of photocurrent due to charge separation was assisted by the built-in potential near the pn homojunction interface that was controlled by doping concentration. The result demonstrated that the pn homojunction interface in a single organic semiconductor layer formed by doping can achieve efficient charge separation and provide a suitable alternative to the donor/acceptor interface that has been considered necessary for photoconversion in organic SCs.