Enhancement of Structural, Optical and Photoelectrochemical Properties of n-Cu2O Thin Films with K Ions Doping toward Biosensor and Solar Cell Applications

n-type Cu2O thin films were grown on conductive FTO substrates using a low-cost electrodeposition method. The doping of the n-Cu2O thin films with K ions was well identified using XRD, Raman, SEM, EDX, UV-vis, PL, photocurrent, Mott-Schottky, and EIS measurements. The results of the XRD show the creation of cubic Cu2O polycrystalline and monoclinic CuO, with the crystallite sizes ranging from 55 to 25.2 nm. The Raman analysis confirmed the presence of functional groups corresponding to the Cu2O and CuO in the fabricated samples. Moreover, the samples' crystallinity and morphology change with the doping concentrations which was confirmed by SEM. The PL results show two characteristic emission peaks at 520 and 690 nm which are due to the interband transitions in the Cu2O as well as the oxygen vacancies in the CuO, respectively. Moreover, the PL strength was quenched at higher doping concentrations which reveals that the dopant K limits e-/h+ pairs recombination by trapped electrons and holes. The optical results show that the absorption edge is positioned between 425 and 460 nm. The computed Eg for the undoped and K-doped n-Cu2O was observed to be between 2.39 and 2.21 eV. The photocurrent measurements displayed that the grown thin films have the characteristic behavior of n-type semiconductors. Furthermore, the photocurrent is enhanced by raising the doped concentration, where the maximum value was achieved with 0.1 M of K ions. The Mott-Schottky measurements revealed that the flat band potential and donor density vary with a doping concentration from -0.87 to -0.71 V and 1.3 x 10(17) to 3.2 x 10(17) cm(-3), respectively. EIS shows that the lowest resistivity to charge transfer (Rct) was attained at a 0.1 M concentration of K ions. The outcomes indicate that doping n-Cu2O thin films are an excellent candidate for biosensor and photovoltaic applications.

Automated summary

N-type Cu2O thin films were grown on FTO substrates using a low-cost electrodeposition method. The doping of the thin films with K ions was confirmed through various measurement techniques. The results showed the presence of Cu2O and CuO phases in the fabricated samples, with changes in crystallinity and morphology observed with different doping concentrations. The optical properties indicated interband transitions in Cu2O and oxygen vacancies in CuO, with the absorption edge positioned between 425 and 460 nm. Photocurrent measurements revealed the characteristic behavior of n-type semiconductors, with enhanced photocurrent at higher doping concentrations. Mott-Schottky and EIS measurements provided information on the flat band potential, donor density, and resistivity to charge transfer, with the lowest values observed at 0.1 M concentration of K ions. Overall, the results suggest that doping n-Cu2O thin films have potential applications in biosensors and photovoltaics.