Donor/Acceptor Photovoltaic Cells Fabricated on p-Doped Organic Single-Crystal Substrates

In this study, the operation of donor/acceptor photovoltaic cells fabricated on homoepitaxially grown p-doped rubrene single-crystal substrates is demonstrated. The photocurrent density is dominated by the sheet conductivity (σ_□) of the p-type single-crystal layer doped to 100 ppm with an iron chloride (Fe₂Cl₆) acceptor. A 65 mm thick p-type rubrene single-crystal substrate is expected to be required for a photocurrent density of 20 mA·cm^-2. An entire bulk doping technique for rubrene single crystals is indispensable for the fabrication of practical organic single-crystal solar cells.