Optimal Blending of PbSe and CdSe in Polycrystalline PbCdSe Nanocomposite Film: Improved Carrier Multiplication and Enhanced Photoconversion Efficiency

The present work reports galvanostatic electro-co-deposition of n-PbCdSe semiconductor (SC) films on FTO substrate from the respective precursors. Self-designed matrices were formulated at variable concentrations of Pb²⁺ in the deposition medium. The semiconductor films constitute an intermixed structure of close-packed PbSe and CdSe nanoparticles (NPs), and the band gap (E_g) was effectively tuned in the range 0.99-1.47 eV for the variable compositions. Energy dispersive spectroscopy studies revealed that Cd exists in low level in the film matrix compared to Pb, presumably due to competitive deposition kinetics of the two chalcogenide compounds and the crystallite sizes determined from XRD studies, ranges between 15 and 12 nm, which corresponds to the size quenching of SC-NPs with increased Pb²⁺ concentration. The durability studies identify the most stable film developed at 0.025 M Pb²⁺ concentration. PbSe materials are typically characterized with impact ionization which effectively induces carrier multiplication (CM) in the quasi Type-II PbCdSe composite, exhibiting reasonably high photoconversion efficiency (PCE) of 6.14% with current output of 19.2 mA cm^-2 for the optimal PbCdSe film.