Improving photodetector performance of PANI nanofiber by adding rare-earth La${}_2$O${}_3$ nanoparticles

Nanocomposites based on Polyaniline (PANI) nanofibers (NFs) and Lanthanum oxide (La${}_2$O${}_3$) nanoparticles (NPs) were successfully synthesized using hydrothermal and chemical methods, respectively. Thin films of pure PANI and PANI/La${}_2$O${}_3$ nanocomposites have been deposited by spin-coating technique on both n-Si and glass substrates. The prepared thin films have been tested using XRD, FE-SEM, and UV-Vis and were examined as photodetectors. The XRD pattern showed the crystalline nature of PANI NFs' film and the cubic structure of PANI/La${}_2$O${}_3$ films. FE-SEM images of pure PANI proved that the film prepared has a nanofiber-like structure, whereas the PANI/La${}_2$O${}_3$ nanocomposite films proved that La${}_2$O${}_3$ NPs capped with PANI NFs. The UV-Vis spectrum of pure PANI showed the absorption peaks of B and Q bands at 340 and 651 nm, while for PANI/La${}_2$O${}_3$ films, the position of the two bands shifted to 320 and 620 nm revealing a charge transfer between the PANI NFs and La${}_2$O${}_3$ NPs. The optical band gap value of PANI/La${}_2$O${}_3$ hybrid nanocomposite films decreases from 2.97 to 2.81 eV for B-band and from 1.49 to 1.43 eV for Q-band upon increasing the La${}_2$O${}_3$ content from 1 to 4 vol.% in the PANI NFs. On the other hand, incorporating La${}_2$O${}_3$ into PANI showed remarkably improved photodetector performance of the system. The maximum sensitivity values of the photoconductive detectors were observed for PANI/La${}_2$O${}_3$ nanocomposites deposited on an n-Si substrate which were approximately 342.72 and 5069.69% at 660 and 965 nm, respectively.