High-Efficiency BODIPY-Based Organic Photovoltaics

Abstract

A benzannulated boron dipyrromethene\n(BODIPY, bDIP) molecule exhibiting\nstrong absorption at 640 nm was synthesized. The organic dye was used\nin an organic solar cell as the electron donor with C₆₀ as the acceptor. The BODIPY dye demonstrated the best performance\nin lamellar architecture (indium tin oxide (ITO)/bDIP/C₆₀/bathocuproine/Al), giving power conversion efficiency up to 4.5%\nwith short-circuit current (<i>J</i>_SC) of 8.7\nmA/cm² and an open-circuit voltage (<i>V</i>_OC) of 0.81 V. Neutron reflectivity experiments were performed\non the bilayer film to investigate the thickness dependence of <i>J</i>_SC. A 13 nm mixed layer was found to be present\nat the donor/acceptor interface\nin the bilayer device, formed when the C₆₀ was deposited\nonto a room temperature bDIP film. Planar-mixed heterojunction devices\nwere fabricated to understand the extent of spontaneous mixing between\nthe donor and acceptor materials. The native mixed region in the bilayer\ndevice was shown to most resemble 1:3 bDIP:C₆₀ layer in\nthe structure: (ITO/bDIP/bDIP:C₆₀ blend/C₆₀/bathocuproine/Al).