Near-Infrared Azadipyrromethenes as Electron Donor for Efficient Planar Heterojunction Organic Solar Cells

We report the use of three solution processable azadipyrromethene (ADPM) based compounds, i.e., ADPM, BtF2-chelated ADPM (BF2-ADPM), and B,O-chelated ADPM (BO-ADPM), as electron donors in planar hetero-junction solar cells. These small molecules possess exceptional light harvesting capability with high extinction coefficients (similar to 1 x 10(5) M-1 cm(-1) in solutions) and broad absorption spectra up into the near-infrared region. Planar heterojunction organic solar cells, consisting of a solution processed electron donor layer and a vapor deposited C-60 acceptor layer, have been constructed to give power conversion efficiencies of 0.56, 0.69, and 2.63% for ADPM, BF2-ADPM, and BO-ADPM, respectively, under AM 1.5G simulated 1 sun solar illumination. A high open circuit voltage (V-oc) of similar to 0.8 V was achieved for the BO-ADPM/C-60 device, which is among the highest reported values for organic solar cells with photocurrent generation in the near-infrared region beyond 1.5 eV.