Tailoring the PEDOT:PSS hole transport layer by electrodeposition method to improve perovskite solar cells

Abstract

Organometallic halide perovskites have emerged in the last decade as promising light absorbers for solar cell development. These devices require functional layers for both generated hole and electron extraction and transport. Among the hole transporting materials (HTM), poly(3,4-ethylenedioxythiophene) poly-(styrenesulfonate) or PEDOT:PSS layers have been widely obtained from a colloidal suspension. As an alternative, PEDOT:PSS can also be electrochemically deposited, allowing for synthesis control and performance design. In this study, the effect of the electrodeposition method of PEDOT on its HTM properties and solar cell efficiency was evaluated. The result showed a decrease in the HTM charge carrier density with the increase in the polymerization potential. When this potential is around 1.5 V (vs Ag/AgCl), the Raman spectra suggest the formation of side groups in the polymer chains resulting from over-oxidation. HTMs with a high charge carrier density increased the short-circuit current density (Jsc) and fill factor (FF) but reduced the open-circuit potential (Voc) of the solar cells. To avoid overoxidation, low synthesis potentials were applied. With this strategy, a 15.0% power conversion efficiency (PCE) was achieved using the galvanostatic method at 0.1 mA cm−2, where the applied potential was ∼1 V. Consequently, this work paves the way for the optimization of the solar cell by simply controlling the electrodeposition potential of the PEDOT as HTM.