Organic solar cells with sensitivity extending into the near infrared - art. no. 200508

We describe an organic photovoltaic cell based on a tin(II) phthalocyanine (SnPc)/C-60 donor/acceptor heterojunction with sensitivity at wavelengths of lambda>900 nm. We find that the low hole mobility in polycrystalline thin films of SnPc, mu(h)=(2 +/- 1)x10(-10) cm(2)/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-A-thick layer of SnPC yields solar cell external quantum efficiencies of up to 21% at lambda=750 nm. With the double heterostructure of indium-tin oxide/100 A copper phthalocyanine/50 A SnPc/540 A C-60/75 A 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. (c) 2005 Americian Institute of Physics.