Bifunctional enhancement of photodetection and photovoltaic parameters in graphene/porous-Si heterostructures by employing interfacial hexagonal boron nitride and bathocuproine back-surface passivation layers

Abstract

High-density pores formed on Si are effective for enhancing the light absorption of Si, thereby improving the efficiency of graphene (GR)/Si-heterojunction optoelectronic devices. Insulating hexagonal boron nitride (h-BN) is highly attractive as an interfacial material between GR and semiconducting materials for heterostructures because of the large bandgap/small lattice mismatch with GR. Here, we first report the bifunctional enhancement of photodetection and photovoltaic parameters in (trifluoromethanesulfonyl)-amide-doped GR (TFSA-GR)/porous Si (PSi)/Si heterostructures by employing a h-BN interlayer at the TFSA-GR/PSi interface and a bathocuproine (BCP) passivation layer on the Si back surface. The concurrent use of h-BN and BCP layers makes it difficult for the electrons to overcome the energy barriers as well as for the photo-induced electrons/holes to be recombined at the interfaces, thereby decreasing the dark current (DC) and facilitating the photocarrier collection, respectively. These effects result in remarkable improvements of the photoresponse and energy harvesting. In particular, the specific detectivity is almost 100 times enhanced at zero bias, i.e., under self-powered. The devices also show excellent long-term stability by maintaining 98 and 74% of their original photocurrent and DC, respectively, when kept in air for 2000 h. These results suggest that TFSA-GR/h-BN/PSi/Si/BCP heterostructures are very promising for application in self-powered or self-driving multifunctional optoelectronic devices.