Conductive polymer PEDOT:PSS back contact for CdTe solar cell

Two types of superstrate glass/ITO/CdS/CdTe PV structures were prepared by high vacuum evaporation technique with (i) activation of CdS layer and CdS/CdTe bi-layer structure step-by-step and (ii) activation of CdS/CdTe bi-layer structure. The activation was performed by annealing the structures with CdCl₂ in air at 400 °C for 15 min. Main conditions for CdS and CdTe thin films deposition and following treatment were selected from the literature data with the purpose to prepare and compare complete CdTe solar cells with standard p + Cu_xTe back contact and conductive polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS) back contact. Obtained layers and structures were characterized using the XRD, SEM and I-V methods. Both the methods of activation treatment give comparable results from the point of view PV properties of complete solar cells. It was found that highly conductive PEDOT:PSS intermediate layer can significantly improve the back contact characteristics of CdTe. However these hybrid structures need to be further optimized to compete successfully with conventional inorganic back contacts in complete CdTe solar cells.