Favored for its low cost and relatively high efficiency (22.1% in 2016), Cadmium Telluride (CdTe) solar cells are popular among the thin film solar cells, and there are still room for improvement. CdTe has a high electron affinity (about 4.5eV) and as a result when typical metal contacts are used, a good ohmic contact is not created, and a Schottky barrier is formed at the back-contact junction. This barrier impedes current flow and lowers cell performance. In exploring new back contact material, we have found that conducting polymer such as PEDOT:PSSPSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate] with a high work function (~5.4 eV) can be used as back contact to CdTe and showed promising results.

In this work, we show that by mixing DMSO (Dimethyl sulfoxide) with PEDOT:PSS with different ratios (5% DMSO and 20% DMSO), we can modify the property of the polymer and change the barrier height at the CdTe/polymer back contact, which affects the solar cell efficiency.