Very-high-efficiency double-heterostructure copper phthalocyanine/C-60 photovoltaic cells

We demonstrate an external power conversion efficiency of (3.6 +/-0.2)% und er AM1.5 spectral illumination of 150 mW/cm(2) (1.5 suns) with vacuum-depos ited copper phthalocyanine/C-60 thin-film double-heterostructure photovolta ic cells incorporating an exciton-blocking layer (EBL). We show that the an ode work function influences the photocarrier collection characteristics th rough the built-in electric field. The cell parameters are less sensitive t o the cathode work function, which is attributed to cathode-induced defect states in the EBL energy gap. The presence of these defect states also expl ains the surprisingly low resistance of the EBL to electron transport. We a nticipate significant further improvements in power conversion efficiency b y employing optimal structures in light-trapping geometries. (C) 2001 Ameri can Institute of Physics.