Bandgap Tuning of Sm and Co Co-doped BFO Nanoparticles for Photovoltaic Application

Abstract

Multiferroic $BiFeO_3$ (BFO) with bandgap energy ($E_g$) between 2.2 eV to 2.7 eV is a potential candidate for photovoltaic (PV) application. However, the efficiency of BFO based PV solar cells is reportedly still too low (less than 2%) to be used for practical applications. Reducing $E_g$ of BFO without compromising the ferroelectric properties is a big challenge to the scientific community to obtain power conversion efficiencies beyond the maximum value of 26.6% reported in general for silicon based hetero-structure PV solar cells. In this context, samarium (Sm) and cobalt (Co) co-doped BFO ($Bi_{0.9}Sm_{0.1}Fe_{0.9}Co_{0.1}O_3$) nanoparticles were synthesized using the sol-gel method. X-ray diffractometry was employed to determine the structure of synthesized nanoparticles. A well-defined crystalline structure of co-doped BFO nanoparticles was confirmed. Field emission scanning electron microscopy was carried out to study grain morphology of synthesized nanoparticles. Sm and Co dopants have been shown to reduce grain size significantly from 68.3 nm to 18.5 nm. An UV-Vis-NIR spectrophotometer was used to measure diffuse reflectance to calculate $E_g$. A significant reduction of $E_g$ down to 1.50 eV of co-doped BFO compared to undoped and or single doped counterpart has been manifested.