Single nanoflake-based PtSe2 p–n junction (in-plane) formed by optical excitation of point defects in BN for ultrafast switching photodiodes

Abstract

Here, novel lateral PtSe₂ p–n junctions are fabricated based on the PtSe₂/BN/graphene (Gr) van der Waals heterostructures upon the illumination of visible light via the optical excitation of the mid-gap point defects in hexagonal boron nitride (h-BN). A stable photo doping effect was achieved for tuning the polarity of PtSe₂-based field-effect transistors (FETs). The constructed diodes display excellent rectifying performance, with a rectification ratio of up to ∼1.0 × 10⁵ and an ideality factor of ∼1.3. Distinctive self-biased photovoltaic behavior was detected, specifically in the positive open-circuit voltage (V_oc = 0.32 V) at zero source–drain current (I_ds), and also the negative short-circuit current (I_sc = 16.2 nA) at zero source–drain voltage (V_ds) generated for the p–n diode state upon the illumination of incident light (600 nm, 40 mW cm⁻²). Moreover, output V_oc switching behavior was achieved for the p–n diode state by switching the input light signal on and off, with a photoresponse over the broadband spectral range of 200–1200 nm. Various photovoltaic parameters were also measured. Also, using this elegant approach, homoinverters were fabricated that reached a maximum gain of ∼30 (V_DD = 2 V). These findings pave the way to developing self-biased photovoltaic devices by exploiting 2D noble metal dichalcogenide materials.