Fig. 3. Enhancement of NIR sensitivity by green light illumination.

(A) EQE as function of wavelength measured with and without additional green (540 nm) light illumination, showing an enhancement in the NIR region. Green light intensities are indicated in the legend. (B) Corresponding EQE max (∼830 nm) obtained with and without green illumination plotted as a function of applied bias voltage. For comparison, EQE_max under the additional 60 mW cm⁻² 540-nm light is considered. The inset shows the relative enhancement of EQE due to the additional green light as a function of applied bias expressed as the ratio of EQE_max with and without green light. Data are extracted from EQE spectra (fig. S6). (C) Spectral responsivity (SR) of tandem-like PD (under 60 mW cm⁻² 540-nm illumination) compared to that of commercial Si PD. Colored circles indicate the SR at 850 nm for our device, Si and ideal PDs having 100% EQE. (D) Detectivity at different wavelengths measured at 0 V for tandem-like PD under additional green light (blue solid line) and for commercial Si reference PD (i_n = 1.2 × 10⁻¹⁴ A Hz^−1/2) (gray dashed line). Graph in semilogarithmic scale is provided in fig. S10. (E) Comparison of noise current–based specific detectivity (D^*) of our device with state-of-the-art NIR narrowband solution–processed photodetectors (both PD and photomultiplication types, indicated in the legend as PD-type and PM-type, respectively) and with main commercial inorganic PDs, namely, Si (Thorlabs, FDS100-CAL), Ge (Thorlabs, FDG03-CAL), and InGaAs (Thorlabs, FGA21-CAL). The comparison focuses on reported devices with design wavelength lying in the NIR region between 700 and 1200 nm. Further details are provided in fig. S10.