Photovoltaic effect in multiphase Bi-Mn-O thin films

Area of Science:

• Materials Science
• Solid State Physics
• Renewable Energy

Background:

• Bismuth-manganese-oxide (Bi-Mn-O) thin films are explored for photovoltaic applications.
• Epitaxial growth of Bi-Mn-O films on single crystal substrates is achievable.
• Strontium titanate (STO) is a common substrate for thin film deposition.

Purpose of the Study:

• To investigate the solar power conversion efficiency of Bi-Mn-O thin films.
• To determine the effect of the Bi/Mn ratio on photovoltaic properties.
• To understand the relationship between film composition, band alignment, and device performance.

Main Methods:

• Thin films of Bi-Mn-O were grown on (111) Nb-doped SrTiO3 substrates using pulsed laser deposition (PLD).
• Film composition was varied by adjusting the Bi/Mn ratio during growth.
• Photovoltaic performance was evaluated using a sun simulator (AM 1.5 G).
• Epitaxial growth and phase composition (BiMnO3 and Mn3O4) were confirmed.

Main Results:

• An external solar power conversion efficiency of approximately 0.1% was achieved.
• Varying the Bi/Mn ratio significantly impacted photo-induced voltage and photocurrent.
• Higher Bi/Mn ratios (closer to unity) led to increased power conversion efficiency.
• Epitaxial growth of both BiMnO3 and Mn3O4 phases was observed.

Conclusions:

• The Bi/Mn ratio is a critical factor for optimizing photovoltaic efficiency in Bi-Mn-O/STO heterostructures.
• Improved efficiency at higher Bi/Mn ratios is attributed to more favorable energy band alignment at the film/substrate junction.
• This work highlights the potential of tailored Bi-Mn-O films for solar energy conversion.