Fig. 1. (Color online) (a) The schematic of n⁺−p−p⁺ diode in the forward biased steady state condition for establishing the theoretical background of the COCVD, and (b) the representatively theoretical OCVD curve at which three distinctive regions could be distinguished corresponding to different injection levels, i.e., high level (1^st region), intermediate level (2^nd region), and low level (3^rd region).

Fig. 2. (Color online) (a) The schematic developed MOCVD test setup, with detailed associated devices, and (b) the real 3D arranged componential parts on the optical tray.

Fig. 3. (Color online) The three developed PbS photodetectors developed in this study (a), (b), and (c).

Fig. 4. (Color online) (a) The XRD pattern of the developed PbS thin film in the scanning range from 20° to 80°, and (b) the Williamson−Hall plot.

Fig. 5. (Color online) Raman spectroscopy of the PbS thin film, at which the Raman shift is deconvoluted into the componential peaks.

Fig. 6. (Color online) Transmittance and derived absorption coefficient spectra of 1 µm PbS thin film as function of the wavelength.

Fig. 7. (Color online) The TRPL signal over time for the 1 µm PbS thin film at various wavelength excitation.

Fig. 8. (Color online) (a) The dependence of V_oc signal overtime at distinct chopper frequency ranging from 100 to 400 Hz, with power supply of 24 W to the light source, and (b) at various power supplies from 12 to 36 W at 300 Hz of chopper frequency.

Fig. 9. (Color online) The analyzing process in the MOCVD setup. (a) and (c) The dependence of V_oc signal overtime at a scanning time; (b) and (d) typical regions in the OCVD curves corresponding to the fitting with either linear or bi-exponential decay function, which allows to indirectly estimate the minority carrier lifetimes of developed thin films; and (e) the statistical estimation for the minority carrier lifetimes derived from 50 MOCVD curves corresponding to the 1^st, 2^nd, and 3^rd regions.