Bulk-heterojunction photovoltaic devices based on donor-acceptor organic small molecule blends

We present a systematic study on photovoltaic devices that combine an organic small molecule photoactive donor-acceptor bulk heterojunction system with controlled doping of the charge transport layers. The doped transport layers are formed using high vacuum co-evaporation deposition technique (i.e. co-sublimation of matrix and dopant). Solar cell devices have been fabricated based on zinc-phthalocyanine (ZnPc) as donor (D) and fullerene (C-60) as electron acceptor (A) with doped charge transport layers. The cells show a short circuit current, I-sc = 1.5 mA/cm(2), an open circuit voltage, V-oc = 450 mV, a fill factor, FF = 0.5, and a power conversion efficiency, eta(e) = 3.37% under 1/10 sun (10 mW/cm(2)) white light illumination. In addition, these bulk-heterojunction photovoltaic devices were characterized under 1 sun (100 mW/cm(2)) white light illumination showing I-sc = 6.3 mA/cm(2), V-oc = 500 mV, and eta(e) = 1.04%. We have observed that the performance of such 'bulk-heterojunction' photovoltaic devices is critically dependent on the transport properties of the interpenetrating network D/A system and doped charge transport layers. (C) 2002 Elsevier B.V. All rights reserved.