Organic solar cells with sensitivity extending into the near infrared

We describe an organic photovoltaic cell based on a tin(II) phthalocyanine (SnPc) C60 donor/acceptor heterojunction with sensitivity at wavelengths of λ900 nm. We find that the low hole mobility in polycrystalline thin films of SnPc, μh = (2±1) × 10-10 cm2 V s, prevents the use of thick layers, leading to low fill factors and therefore low-power conversion efficiencies. However, owing to its large absorption coefficient, a 50-Å -thick layer of SnPC yields solar cell external quantum efficiencies of up to 21% at λ=750 nm. With the double heterostructure of indium-tin oxide/ 100 Å copper phthalocyanine/ 50 Å SnPc540 Å C60 75 Å bathocuproine/Ag, we obtain a power conversion efficiency of (1.0±0.1) % under 1 sun standard AM1.5G solar illumination and efficiencies of (1.3±0.1) % under intense (10 suns) standard AM1.5G solar illumination.