Comparison of short and long wavelength absorption electron donor materials in C60-based planar heterojunction organic photovoltaics

Buckminsterfullerene, C60-based planar heterojunction (PHJ) organic photovoltaics (OPVs) have been created using a short wavelength absorption (λmax = 490 nm) electron-donating bis(naphthylphenylaminophenyl)fumaronitrile (NPAFN). NPAFN exhibits a hole mobility greater than 0.07 cm2 V−1 s−1 as determined by its field-effect transistor. It can be attributed to such hole mobility that enables a thin layer (<10 nm) NPAFN in PHJ OPV, ITO/NPAFN/C60/bathocuproine/Al. Because of the low lying HOMO energy level (5.75 eV) of NPAFN and relatively high ionization potential ITO (∼5.58 eV), such OPVs exhibit a very high open circuit voltage of ∼1.0 V, relatively high fill factor of 0.60, and a relatively high shunt resistance of 1100 Ω cm−2, which all compensate for a relatively low short circuit current of 3.15 mA cm−2 due to the short absorption wavelength and inferred short exciton diffusion length of NPAFN. Altogether, NPAFN OPVs display a power conversion efficiency (ηPC) of 2.22%, which is better than other long wavelength absorption materials in similar PHJ OPVs, such as pentacene (λmax 670 nm, HOMO 5.12 eV, ηPC 1.50%) and copper phthalocyanine (λmax 624, 695 nm, HOMO 5.17 eV, ηPC 1.43%).

Graphical abstractBis(naphthylphenylaminophenyl)fumaronitrile (NPAFN): High Carrier mobility. Field-Effect Transistor Material for Planar Heterojunction Organic Photovoltaics with Enhanced Efficiency and Large Open Circuit Voltage of 1 VFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► OPVs have been created using short wavelength absorption of NPAFN. ► We report that NPAFN exhibits a high hole mobility as determined by OFET. ► NPAFN OPVs display the power conversion efficiency (ηPC) of 2.22%.