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

Abstract

As a hole-transport layer (HTL) material, poly(3,4-ethylenedioxythiophene):polystyrene-sulfonate (PEDOT:PSS) was often criticized for its intrinsic acidity and hygroscopic effect that would in the long run affect the stability of perovskite solar cells (Pero-SCs). As alternatives, herein water-soluble two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS and WS 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 postheating) 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 MoS and WS, respectively, whereas the Pero-SCs with PEDOT:PSS showed a highest PCE of only 12.44%. These are up to date the highest PCEs using 2D TMDs as HTLs. After being stored in a glovebox for 56 days, PCEs of the Pero-SCs using MoS and WS HTLs remained 78 and 72%, respectively, whereas 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 application as new generation of HTLs aiming at high performance and long-term stable Pero-SCs.

The damaging effects of the acidity in PEDOT:PSS on semiconductor device performance and solutions based on non-acidic alternatives

“…A different approach can involve using lithium intercalation and exfoliation method, as reported by Li and co-workers. 87 The resulting MoS 2 and WS 2 films were used in perovskite solar cells and showed superior performance when compared to PEDOT:PSS-based devices. When stored in ambient conditions, the PCE of the PEDOT:PSS containing device almost degraded completely after 35 days but devices containing MoS 2 and WS 2 showed 78% and 72% of their average PCEs, respectively, after 56 days, highlighting the greater stability that can be achieved by using transition metal dichalcogenide layers.…”

Dopant‐Free Hole Transporting Materials for Perovskite Solar Cells

“…A thin MoO x layer can prevent photobleaching of the MAPbI 3 film and mitigates decomposition. Two water‐soluble two dimensional transition metal dichalcogenide, MoS 2 and WS 2 are used as HTM in PSCs in a study by Huang et al The highest PCEs of 14.35 and 15.00% were obtained for the PSCs with MoS 2 and WS 2 , respectively. In a very recent study, Qin et al have achieved high PCE of 17.19% on glass and 15.53% on flexible PET substrates, introducing and employing a novel copper‐chromium binary metal oxide as HTM for PSCs .…”

Beneficial impact of materials with reduced dimensionality on the stability of perovskite-based photovoltaics

“…Nonetheless, MoS 2 is a good example of versatility these 2D chalcogenides offer, since it can govern both electron and hole transport, either as an interlayer or a dopant. In both cases, significant improvement of device stability and energy alignment with adjacent layers were reported for both inverted and normal perovskite solar cells [35,36]. Kakavelakis et al demonstrated potential of MoS 2 to improve operational stability of inverted perovskite solar cells by suppressing light-induced decline of photocurrent [37].…”