Upconversion Absorber on 2D Charge Transporter for High Responsivity Broadband Photodetectors
Sandip Ghosh1, Surojit Chattopadhyay1*
1Institute of Biophotonics, National Yang Ming Chiao Tung University, Taipei City, Taiwan
* Presenter:Surojit Chattopadhyay, email:sur@nycu.edu.tw
Hybrid photodetectors (PDs) with high responsivity (R) have emerged as an alternative to conventional semiconductor PDs. The low R of the semiconductor PDs and the dynamic range limited by the bandgap, could be solved using the hybrid design. However, the use of multiple interfaces in the hybrid design slows down the charge transport. The narrow dynamic range, limited in the IR, compels us to incorporate alternative IR active materials. Here, we report the fabrication of three PD devices based on NIR absorbing upconversion nanoparticles (UCNPs) incorporated with two-dimensional (2D) nanomaterials, such as Graphene, MoS2, and further speeding up the device with plasmonic AuNRs. The MoS2-UCNPs PD devices show a broadband (325-1064 nm) photoresponse with high R>1000 A/W and detectivity of 1015 Jones, albeit with an extremely slow response time (~15-20 s) [1]. The response speed could be partially solved by using the higher mobility graphene charge transporter. In addition to a broadband photoresponse (405-1064 nm), the Graphene-UCNPs PD device shows a record R of ~104 A/W in this class of devices and a relatively quick response time of ~2.4 s [2]. The incorporation of the plasmonic AuNRs in this device (Graphene-UCNPs-AuNRs) could speed up the device to around ~80 ms and retain high R [3]. A proper optimization of the UCNP: AuNR ratio, or using a resonant plasmonic chip could speed up this hybrid device and be competitive in the class.

Keywords: UCNPs, Photodetectors, Graphene, MoS2, AuNRs