Defect-mediated negative differential resistance and photoconductive enhancement in graphene oxide decorated SnSe₂...

Pristine tin diselenide (SnSe₂) and graphene oxide-decorated SnSe₂ (SnSe₂-GO) nanocomposites were synthesized via a facile chemical bath deposition (CBD) method and investigated the photoconductive and nonlinear electrical transport properties. Structural and spectroscopic analyses confirmed the formation of highly crystalline hexagonal SnSe₂ and the successful incorporation of GO within the composite structure. Temperature-dependent electrical measurements yielded activation energies of 0.12 and 0.09 eV for pristine SnSe₂ and SnSe₂-GO, respectively, indicating enhanced carrier transport in the composite. Photoconductivity measurements revealed an approximately 180-fold enhancement in photocurrent under 35 000 lux illumination following GO incorporation. This remarkable improvement, accompanied by an increase in the photoresponse exponent from 0.18 to 0.80, is attributed to more efficient interfacial charge separation, reduced trap-assisted recombination, and enhanced carrier transport. In contrast, pristine SnSe₂ exhibited pronounced asymmetric negative differential resistance (NDR) behaviour that was strongly dependent on precursor molarity, Sn stoichiometry, and voltage sweep direction. The systematic shift of the NDR peak with increasing selenium content suggests a defect-mediated transport mechanism governed by selenium-vacancy-related deep-level states. Furthermore, the observed hysteresis and non-zero-bias crossing behaviour indicate a history-dependent electrical response associated with charge accumulation and trapping within the nanosheet network. Interestingly, GO incorporation completely suppressed the NDR response while simultaneously enhancing photoconductivity, which is attributed to partial passivation of electrically active defect states by residual oxygen-containing functional groups in the GO-derived carbonaceous phase and improved interfacial charge transfer. These findings demonstrate that defect engineering and interfacial coupling provide effective strategies for tailoring the photoconductive and nonlinear electrical transport properties of SnSe₂-based nanocomposites for optoelectronic and nanoelectronic applications.