Dr. Soo Young Kim, Professor, School of Chemical Engineering and Materials Science, Chung-Ang University, Korea.

Speech Title: Stability extension of photovoltaic cells using 2D materials

Abstract: Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely use as hole extraction layer (HEL) in organic photovoltaics (OPVs) and perovskite solar cells (PSCs) on account of its suitable band gap alignment with active layer and easy-fabrication via solution process. However, its acidic and hygroscopic nature makes it inappropriate for the real product. To overcome the challenges caused by PEDOT:PSS, we have tried to use two dimensional materials instead of PEDOT:PSS as HEL in OPVs and PSCs, which include graphene oxide (GO), UV/ozone treated graphene, transition metal dichalcogenides (MoS₂, WS₂, TaS₂, TiS₂) and (NH₄)₂WS₄. GO was synthesized by using Hummers' method. Graphene and transition metal dichalcogenides were prepared by chemical vapor deposition method or sonication process.

The current density-voltage characteristics of PSCs based on PEDOT:PSS, MoS₂, WS₂, and GO HEL are compared. The PCE of PEDOT:PSS based PSCs is 9.93%. The PCEs of MoS₂, WS₂, and GO based PSCs are 9.53, 8.02, and 9.62 %, respectively. Although PCE of WS₂ based PSC was somewhat lower than that of PEDOT:PSS based ones, the PCE of GO and MoS₂ based solar cell were similar to that of PEDOT:PSS based one, suggesting that GO and MoS₂ HELs can be substituted for PEDOT:PSS. Therefore, it is considered that two dimensional materials could be used as HEL in OPVs and PSCs.