An air-stable ultraviolet photodetector based on mesoporous TiO2/spiro-OMeTAD

Abstract

A hybrid organic/inorganic heterojunction structured photodetector has attracted much attention due to its high device stability and ease of fabrication. In this work, an ultraviolet photodetector with the configuration of spiro-OMeTAD/mesoporous TiO₂/compact TiO₂ was developed. The small molecule of spiro-OMeTAD was introduced as the active layer, owing to its fast response to the ultraviolet light and high glass transition temperature (T_g). The mesoporous TiO₂ layer with a large specific area could accelerate the interface separation of electrons and holes, while the compact TiO₂ layer was used to block the charge leakage between FTO and spiro-OMeTAD. With a 100 nm TiO₂ mesoporous layer, the photodetector displayed a fast response time (<0.02 s), a low dark current density (8.79 nA cm⁻²) and a high detectivity (3.5 × 10¹³ Jones) at 340 nm light wavelength and a 0.60 V voltage output. Besides, the unencapsulated device in air also showed excellent long-term stability (∼2 months) and thermal stability (∼100 °C).