Near-infrared absorbing semitransparent organic solar cells

Abstract

We present efficient, semitransparent small molecule organic solar cells. The devices employ an indium tin oxide-free top contact, consisting of thin metal films and an additional organic capping layer for enhanced light in/outcoupling. The solar cell encorporates a bulk heterojunction with the donor material Ph₂-benz-bodipy, an infrared absorber. Combination of Ph₂-benz-bodipy with C₆₀ as acceptor leads to devices with high open circuit voltages of up to 0.81 V and short circuit current densities of 5-6 mA/cm², resulting in efficiences of 2.2%-2.5%. At the same time, the devices are highly transparent, with an average transmittance in the visible range (400-750 nm) of up to 47.9%, with peaks at 538 nm of up to 64.2% and an average transmittance in the yellow-green range of up to 61.8%.