Single crystalline pentacene solar cells

Pentacene single crystals were grown from the vapor phase and doped with iodine. Schottky-type solar cells were prepared based on these p-type crystals using rf-magnetron sputtered n-type ITO-window layers and Al or Mg back contacts, respectively. The improvement of the photovoltaic properties due to iodine doping is related to (1) a higher conductivity resulting in a lower series resistance of the devices, (2) a shift of the absorption edge leading to a better match to the solar spectrum, and (3) an increased internal quantum efficiency. The devices were analyzed by measurements of the quantum efficiency, current-voltage curves, and capacitance-voltage characteristics. The solar cells exhibit open circuit voltages up to 955 mV, short circuit current densities of 4.5 mA/cm(2), and filling factors in the range of 0.45 resulting in a maximum conversion efficiency of 1.9% for a standard solar spectrum(AM1.5, 100 mW/cm(2)). (C) 2000 Elsevier Science S.A. All rights reserved.