Power losses in bilayer inverted small molecule organic solar cells

Inverted bilayer organic solar cells using copper phthalocyanine (CuPc) as a donor and C-60 as an acceptor with the structure: glass/indium tin oxide (ITO)/ZnO/C-60/CuPc/MoO3/Al, in which the zinc oxide (ZnO) was deposited by atomic layer deposition, are compared with a conventional device: glass/ITO/CuPc/C-60/bathocuproine/Al. These inverted and conventional devices give short circuit currents of 3.7 and 4.8 mA/cm(2), respectively. However, the inverted device gives a reduced photoresponse from the CuPc donor compared to that of the conventional device. Optical field models show that the arrangement of organic layers in the inverted devices leads to lower absorption of long wavelengths by the CuPc donor; the low energy portion of the spectrum is concentrated near the metal oxide electrode in both devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769440]