Interface Engineering in All-Oxide Photovoltaic Devices Based on Photoferroelectric BiFe_0.9Co_0.1O₃ Thin Films

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Bismuth ferrite (BiFeO3) is a promising lead-free photoabsorber for thin-film photovoltaic (PV) devices due to its stability and ferroelectric properties.
• Current BiFeO3-based PV devices suffer from low efficiencies, necessitating strategies to improve charge transport and reduce recombination.
• Interface engineering with selective transport layers is a key approach to enhance device performance.

Purpose of the Study:

• To investigate the influence of incorporating a zinc oxide (ZnO) layer on the ferroelectric and photoresponse characteristics of epitaxial BiFe0.9Co0.1O3 (BFCO) heterostructures.
• To evaluate the impact of the ZnO interface layer on device performance, specifically short-circuit current and responsivity.
• To elucidate the underlying mechanisms, including band energy alignment, responsible for performance enhancements.

Main Methods:

• Fabrication of all-oxide heterostructures comprising BFCO, ZnO, Sn-doped In2O3 (ITO), and La0.7Sr0.3MnO3 (LSMO) electrodes.
• Characterization of ferroelectric and photoresponse properties through coupled measurements.
• Analysis of band energy alignment at the ZnO/BFCO and ITO/BFCO interfaces using complementary studies.

Main Results:

• The ZnO-modified BFCO heterostructures exhibit robust ferroelectricity and stability under ambient conditions.
• Short-circuit current is modulated by ferroelectric polarization by up to 68% under blue monochromatic light.
• The ZnO-modified interface demonstrates significantly higher responsivity and short-circuit current density compared to devices without ZnO, attributed to reduced charge recombination due to lower Fermi level energy at the ZnO/BFCO interface.

Conclusions:

• Incorporating a ZnO interface layer effectively enhances the photoresponse and photovoltaic performance of BFCO-based devices.
• The improved performance is linked to optimized band alignment at the ZnO/BFCO interface, suppressing charge recombination.
• This study highlights the critical role of interface engineering with ZnO for developing efficient and stable BiFeO3-based optoelectronic devices.