Easily Prepared Transparent Electrodes for Low-Cost Semitransparent Inverted Polymer Solar Cells

Abstract

The continuous thin film of silver (Ag) film is important for semitransparent electrodes in polymer solar cells, while the Ag atoms form as non-continuous below a critical thickness. Here, semitransparent inverted polymer solar cells were fabricated using thermally evaporated Ag/germanium (Ge)/Ag as highly transparent electrodes. An ultra-thin Ge film was introduced to modify the growth mode of Ag. The dependence of the device performance and the thickness of the outer Ag film was investigated. Ag/Ge/Ag electrodes exhibited excellent optical and electrical properties, which were proved by the transmittance and reflectance spectra. A champion efficiency of 5.1% was achieved with an open-circuit voltage level of 0.703 V, a short current density of 11.63 mA/cm2, and a fill factor of 63%. The average visible transmittance (300–800 nm) of devices with Ag/Ge/Ag was calculated as 25%.