Plasmonic hot-electron induced narrowband photodetector by using in-situ grown Ag/TiO2 nano-heterojunction thin films

Efficient charge transport of plasmon-induced hot electrons to the semiconductor junction is the key factor to develop hot electron-based electronics devices. In this work, a plasmon induced hot electrons photodetector has been fabricated from an in situ-grown silver (Ag)/titanium oxide (TiO2) nano-heterojunction thin film via a solution-processed technique. This nano-heterojunction thin film has been grown from a sol-gel derived Na2Ti3O7 (NTO) thin film that contains mobile Na ion (Na+) via ion exchange (Na+-> Ag+) and reduction method. This device has been fabricated in photoconductor geometry on a glass substrate. For this device fabrication, a solution-processed SnO2 has been deposited on top of a glass substrate which works as a charge transport layer. Afterward, a nano-heterojunction thin film of Ag-TiO2 has been grown on top of this SnO2, which transfers plasmon-induced hot electrons from Ag nanoparticles to the SnO2 layer via TiO2. This SnO2 layer efficiently transports electrons to the respective electrode due to its high electron mobility. The contribution of Plasmon induced hot carrier to photocurrent generation has been realized through external quantum efficiency (EQE) measurement which shows intense photocurrent generation in the plasmonic absorption region of the nano-heterojunction thin film. As a consequence, the photodetector shows a narrowband photodetection with a peak position at 443 nm and FWHM of 50 nm. The maximum EQE of 1.54 % has been detected at that wavelength under 10 V external bias whereas the responsivity and detectivity under this measurement condition reach to 0.52 A/W and 1.25 x 1010 Jones respectively.