Visible to near-infrared broadband photodetector employing thin film topological insulator heterojunction (p-TlBiSe2/n-Si) diode

[Display omitted] •The p-TlBiSe2 is an exotic topological insulator with less defect and disordered state, has considerable band gap and potential in spintronics and photo electric devices.•The p-TlBiSe2/n-Si heterojunction will synergize the transport property and will open a new dimension for the Si based optical industries.•Our manuscript contains very significant work in the area of heterojunction device fabrications with topological insulators and Si. We realized the heterostructure of quasi-2D-topological insulators films and n-Si for the formation of the p-n diode.•The good rectification ratio (RR ∼ 718 at ± 3 V) and figure of merit (FOM) in p-TlBiSe2/n-Si heterojunction for switching and other electronics applications.•The ultrafast measurements of p-TlBiSe2/n-Si heterojunction showed optical excitation in TlBiSe2 with a strong modification of exciton transitions in Si.•Evidence of efficient charge separation in photoexcited p-TlBiSe2/n-Si heterojunction due to the presence of the charge state (CT).•The p-TlBiSe2/n-Si heterojunction has shown good responsivity and broadband photo detectivity from visible to near-infrared region in dual quadrants.•The 2-diode simulation is used to study the devices for various detrimental mechanisms such as recombination by studying the Current density- Voltage (J-V) and ideality factor-Voltage (n-V) curve. The study gives important insight into the optimization of devices for solar cells. The work presents a study of quasi-2D thin topological insulator film of TlBiSe2 and its heterojunction TlBiSe2/Glass and TlBiSe2/Si by thermal coating. The vibrational modes were identified in both the heterojunctions using Raman spectroscopy with the identification of the surface phonon mode (SPM) in the TlBiSe2/Si heterojunction. Ultrafast dynamics were studied for the relaxation dynamics of the charge carriers in these heterojunctions. The study identified the interface phenomenon in the form of charge states (CT) in TlBiSe2/Si p-n heterojunction. The p-TlBiSe2/n-Si heterojunction showed good p-n diode characteristics with a rectification ratio under the dark. Its optical response was studied by varying optical power (2.37–3.78 µW) and wavelength (500–1900 nm). It showed excellent photoresponse in the visible to near-infrared (NIR) range which peaks at 900 nm wavelength in both forward as well reverse bias. The explanation of its optical and electrical performance was modeled in terms of band structure, surface states, and int