Sensitive Photodetection with Photomultiplication Effect in an Interfacial Eu Complex on a Mesoporous TiO Film.

A simple device structure composed of an interfacial Eu complex on a mesoporous TiO film is developed by a solution process and acts as the high-performance photodetector with photomultiplication phenomena. The electron transfer from the photoexcited organic ligand, 2,2':6',2″-terpyridine (terpy), as a photosensitizer to TiO is accelerated by the reduction level of Eu ions chemically bonding among terpy and TiO, resulting in the generation of a large photocurrent. It is worth noting that its external quantum efficiency is in excess of 10% under applied reverse bias. The corresponding responsivity of the device is also determined to be 464 A/W at an irradiation light intensity of 0.7 mW/cm (365 nm), which is more than 3 orders of magnitude larger than those of inorganic photodetectors. A dark current of the device can be reduced to 10 A/cm by introducing a Eu oxide thin-film layer as a carrier blocking layer at the interface between transparent conducting oxide (TCO) and the TiO layer, and the specific detectivity reaches 5.2 × 10 jones at 365 nm with -3 V. The performance of our organic-inorganic hybrid photodetector surpasses those of existing ultraviolet photodetectors.