Measurement of charge carrier recombination rates in planar hybrid CdS/poly3-octylthiophene solar cells

Abstract

Hybrid bilayer solar cells have been prepared by chemical bath deposition of cadmium sulfide (CdS) thin films on conductive glass and drop cast poly3-octylthiophene (P3OT) solution on top of CdS free surface. Gold contact on P3OT film was thermally evaporated. Transient photoconductance decay method was implemented to determine the charge carrier recombination times in CdS films. The same parameter in P3OT films was estimated by time-of-flight technique. Charge recombination processes in CdS/P3OT interface were studied by transient photovoltage method. The relation between the photovoltaic performance of hybrid cells and charge recombination times at CdS/P3OT interface was analyzed as a function of P3OT film thickness. It is suggested that the ambient oxygen or humidity may originate the increased charge recombination center density in thinner P3OT films and, as a result, deteriorate the short-circuit current density and open-circuit voltage values of the corresponding hybrid cells.