Photocharge generation and transport studies on BFO/poly(3-hexylthiophene) heterojunction

• Fundamental photophysical parameters for BFO/P3HT bilayer have been investigated.
• Obtained results suggest presence of space-charge region.
• BFO/P3HT bilayer shows fast charge transport and relatively short carrier lifetime.

Bismuth ferrite (BFO) is one of the most popular multiferroic oxides and has recently attracted interest of scientific community as a suitable material for light harvesting applications, due to its efficient polarization-governed mechanism of charge separation and ability to generate above-bandgap voltages. Identified as a promising photoferroic material, BFO has been a subject of various photoconversion studies in conjunction with other oxides and polymers commonly found in organic photovoltaics. In this report, we examined fundamental device parameters such as carrier lifetime, charge transport and diffusion coefficient within BFO/polymer bilayer, utilizing transient photovoltage and photocurrent spectroscopy techniques. Tested devices were fabricated via simple and inexpensive solution processing route, using nitrate precursors for BFO synthesis. Obtained results suggest formation of space-charge region within the device causing charge carrier lifetimes extension up to 350 μs in the absence of external voltage bias, as well as fast charge extraction (<20 μs). Finally, we draw comparison between charge recombination and collection processes in order to improve understanding of the way they relate to fill factor, which consequently has a major influence on device efficiency.

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