Fig. 3. MIR photoluminescence spectra of BP–WSe₂ heterostructures.

a MIR PL spectra of thin-film BP (blue lines) and BP–WSe₂ heterostructures (orange lines) at 80 K. b Schematic band diagram of BP–WSe₂ heterostructures. The dashed line denotes the Fermi energy of BP and WSe₂. c MIR PL enhancement in BP–WSe₂ heterostructures as a function of thickness. The solid line is a guide line. d Polarization-resolved MIR PL spectra for the BP–WSe₂ heterostructure with 5-nm-thick BP. The solid line is the fitting curve obtained using the equation I= (I_max − I_min) cos²θ + I_min. Here, θ is the polarization angle referenced to the armchair axis of BP, and I_max and I_min are the PL intensities along the armchair- and zigzag axes, respectively