Enhanced photovoltaic properties in polycrystalline BiFeO_3 thin films with rhombohedral perovskite structure deposited on fluorine doped tin oxide substrates

摘要

Polycrystalline BiFeO_3 thin films have been deposited on fluorine doped tin oxide substrates successfully through a modified chemical solution deposition process based on using N,N-dimethyl-formamide as solvent. Structural analyses show that, N,N-dimethylformamide is beneficial to reduce the structural strain, and hence rhombohedral BiFeO_3 films rather than the conventional pseudocubic ones were obtained. Absorption spectrum indicates that the modified process derived rohombohedral BiFeO_3 has a narrower band gap (2.54 eV) than that of the conventional process derived pseudocubic BiFeO_3 (2.76 eV). The BiFeO_3 shows good photovoltaic properties with indium tin oxide as top electrode. The short circuit current density and open circuit voltage of the heterojunctions are measured to be 0.13 mA/cm~2 and 0.65 V, respectively, much higher than the reported values for the conventional process derived pseudocubic BiFeO_3 based heterojunctions. Our results indicate that the modified process derived rhombohedral BiFeO_3 can induce higher photovoltaic effect compared with the conventional process derived pseudocubic counterpart.