Organic Solar Cells with Open Circuit Voltage over 1.25 V Employing Tetraphenyldibenzoperiflanthene as the Acceptor

Abstract

Organic photovoltaic devices utilizing α-sexithiophene (6T) as a donor and tetraphenyldibenzoperiflanthene (DBP) as an acceptor were fabricated and compared to devices utilizing DBP as a donor and C60 as an acceptor. The 6T/DBP devices exhibit substantially higher open circuit voltage, 1.27 V compared to 0.86 V for DBP/C60, as a consequence of the higher energy charge transfer state formed. The 6T/DBP devices yield short-circuit current of 3.9 mA/cm2, open-circuit voltage of 1.27 V, and fill factor of 0.55, resulting in a power conversion efficiency of 2.8%. Atomic force microscopy studies show that 6T forms textured films on indium–tin oxide, and subsequent deposition of DBP infills the surface. Optical modeling provides insight into the ideal active layer and transport layer thicknesses. A power conversion efficiency of close to 3% is achieved for a fairly large process window of layer thickness combinations. The high open-circuit voltage in conjunction with absorption out to a wavelength of 650 nm make this material combination especially attractive for tandem devices.