Fast-Response, Highly Air-Stable, and Water-Resistant Organic Photodetectors Based on a Single-Crystal Pt Complex

Organic semiconductors demonstrate several advantages over conventional inorganic materials for novel electronic and optoelectronic applications, including molecularly tunable properties, flexibility, low-cost, and facile device integration. However, before organic semiconductors can be used for the next-generation devices, such as ultrafast photodetectors (PDs), it is necessary to develop new materials that feature both high mobility and ambient stability. Toward this goal, a highly stable PD based on the organic single crystal [PtBr2(5,5'-bis(CF₃CH₂OCH₂)-2,2'-bpy)] (or "Pt complex (1o)") is demonstrated as the active semiconductor channel-a material that features a lamellar molecular structure and high-quality, intraligand charge transfer. Benefitting from its unique crystal structure, the Pt-complex (1o) device exhibits a field-effect mobility of ≈0.45 cm² V^-1 s^-1 without loss of significant performance under ambient conditions even after 40 days without encapsulation, as well as immersion in distilled water for a period of 24 h. Furthermore, the device features a maximum photoresponsivity of 1 x 10³ A W^-1, a detectivity of 1.1 x 10¹² cm Hz^½ W^-1, and a record fast response/recovery time of 80/90 μs, which has never been previously achieved in other organic PDs. These findings strongly support and promote the use of the single-crystal Pt complex (1o) in next-generation organic optoelectronic devices.