Graphene 2019 June 25 28 2019 Rome Italy Graphene black phosphorus photodetectors
Heterostructures can be assembled from liquid phase exfoliated (LPE) layered materials (LMs) [1] via inkjet printing with tens m [1] resolution and controllable thickness [2] to make photodetectors (PDs) [2] However, LPE materials are unfavourable compared to chemical vapor deposited and mechanically exfoliated LMs, due to the presence of traps [1] which results in low responsivities ~mA/W [1,2] Here, we fabricate printable PDs based on graphene and black phosphorus (BP) inks (Fig. 1) showing high responsivity >300A/W) and broadband (0.4 2.8 m) detection (Fig. 2) LPE BP is used due to its broadband optical absorption (400 3500nm) [3] and its tuneable layer dependent direct bandgap [3] Photoexcited holes from BP are injected into graphene, leaving behind uncompensated electrons, resulting in photogating. We achieve a photoconductive gain (ratio of carrier life time measured from the device response time to transit time [4]~107 ,broadband (400 2800nm) and fast ~50ms) response time. The dark current shows a 1/f component, with a noise equivalent power~1.88x10 10W/Hz, and a detectivity~107 Jones. The responsivity is at least three orders of magnitude higher than previously reported ink jet printed BP PDs operating at the same spectral range [5] and the operating wavelength range (up to 2.8 m) is ~0.5 m longer compared to state of the art hybrid LMs colloidal quantum dots PDs [6,7]