Water-Soluble 2D Transition Metal Dichalcogenides as the Hole-Transport Layer for Highly Efficient and Stable p–i–n Perovskite Solar Cells

Abstract

As hole transport layer (HTL) material, PEDOT:PSS was often criticized on the intrinsic acidity and hygroscopic effect, which would in long-run affect the stability of perovskite solar cells (Pero-SCs). As alternatives, herein water-soluble 2D transition metal dichalcogenides (TMDs), MoS2 and WS2, were used as HTLs in p-i-n Pero-SCs. It was found that the content of 1T phase in 2D TMDs HTLs is centrally important to the power conversion efficiencies (PCEs) of Pero-SCs, and the 1T-rich TMDs (as achieved from exfoliation and without post-heating) lead to much higher PCEs. More importantly, as PEDOT:PSS was replaced by 2D TMDs, both the PCEs and stability of Pero-SCs were significantly improved. The highest PCEs of 14.35% and 15.00% were obtained for the Pero-SCs with MoS2 and WS2, respectively, while for the Pero-SCs with PEDOT:PSS only showed a highest PCE of 12.44%. These are up to date the highest PCEs using 2D TMDs as HTLs. After being stored in glovebox for 56 days, PCEs of the Pero-SCs using MoS2 and WS2 HTLs remained 78% and 72%, respectively, whilst the PCEs of Pero-SCs with PEDOT:PSS almost dropped to 0 over 35 days. This study demonstrates that water-soluble 2D TMDs have great potential for the application as new generation of HTLs aiming at high performance and long-term stable Pero-SCs.