Highly efficient photovoltaic diode based organic ultraviolet photodetector and the strong electroluminescence resulting from pure exciplex emission

We demonstrate organic photovoltaic (PV) and ultraviolet (UV) photodetector devices using 1,3,5-tris(3-methylphenyl-phenylamino)-triphenyamine and 1,3,5-tris(N-phenyl-benzimidazol-2-yl)-benzene to function as the donor (D) and the acceptor (A), respectively. Two types of structural devices, a planar heterojunction of layer-by-layer and a bulk heterojunction with a D/A blend layer are fabricated, respectively. Under UV-365 irradiation, the PHJ device offers a power conversion efficiency of ∼10%, while the BHJ device behaves with a responsivity of 135 mA/W at −4 V bias. The BHJ device can also obtain a high exciplex electroluminescence (EL). The dependencies of PV and EL performances on exciplex formation were also discussed.