Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener Electrospray deposited MoS 2 nanosheets as an electron transporting material for high efficiency and stable perovskite solar cells Khalid Mahmood a, ⁎ ,1 , Arshi Khalid b,1 , Syed Waqas Ahmad a , Haji Ghulam Qutab a , Madsar Hameed a , Rabia Sharif a a Department of Chemical & Polymer Engineering, University of Engineering & Technology Lahore, Faisalabad Campus, 3½ Km. Khurrianwala - Makkuana By-Pass, Faisalabad, Pakistan b Department of Basic Sciences & Humanities, University of Engineering & Technology Lahore, Faisalabad Campus, 3½ Km. Khurrianwala - Makkuana By-Pass, Faisalabad, Pakistan ARTICLE INFO Keywords: MoS 2 nanosheets Thin films Perovskite solar cells Hysteresis-free Electrospray ABSTRACT For perovskite solar cells (PSCs), the development of low cost, stable and efficient electron transport materials (ETMs) is of prime consideration. Here, we have introduced a scalable electrospraying technique for the direct deposition of hydrotermally synthesized two-dimensional (2D) MoS 2 nanosheets ETMs, onto the fluorine-doped tin oxide (FTO) glass susbtarte to use in PSCs with reduces hysteresis, improved ambient stability and high efficiency. The PSCs fabricated with electrospray deposited MoS 2 nanosheets demonstrate the maximum power conversion efficiency (PCE max ) of 16.17%, that is comparable to the PCEs achieved from compact SnO 2 and TiO 2 ETM based PSCs. The current findings present a new route for the construction of stable and efficient PSCs based on a low-cost and solution- processed MoS 2 nanosheets ETMs. 1. Introduction In recent times, numerous electron transporting materials (ETMs) containing the metal oxides and their composites have been studied to produce the inexpensive and stable hybrid organic-inorganic perovskite solar cells (PSCs) with incredible power conversion efficiencies (PCEs) (Mahmood et al., 2015a, 2017, 2018a; Yang et al., 2017; Luo et al., 2018; Mahmood et al., 2018b; Dong et al., xxxx; Mahmood et al., 2019; Rehman et al., 2019; Liu et al., 2013; McGehee, 2013). Since, these ETMs show a crucial role in transporting and extracting the photo- generated electrons from perovskite absorber layer to fluorine-doped tin oxide (FTO) glass substrate (Jeon et al., 2015; Yang et al., 2017). Thus, the development of novel ETMs as an electron transporting layer (ETL) in PSCs is a critical matter to explore. The photovoltaic com- munities have been mainly focused on the exploration of transition metal oxides namely TiO 2 , ZnO, SnO 2 , WO 3 and ZnSO 4 as ETLs in perovskite devices (Mahmood et al., 2015b; Wu et al., 2016; Mahmood et al., 2018c; Bera et al., 2014; Singh et al., 2017; Murakami et al., 2017; Song et al., 2017). Most of these ETLs, needed high temperature sintering to achieve the electrically conducting phase, which hampers their feasibility in flexible electronics. Moreover, ZnO ETLs also suffer from poor device stability due to the existence of hydroxyl groups on the oxide surface. However, SnO 2 ETMs demonstrated comparatively better device stability, but it can also degrade in high temperature environment. Hence, there is a real motivation behind the exploration of a stable and low temperature solution-processed novel ETMs for ef- ficient PSCs. Thin films of inorganic compounds having layered-structures such as transition metal dichalcogenide (TMDC), particularly MoS 2 have recently drawn incredible attention of the perovskite researchers as a hole transport material, owing to their high carrier mobility and in- trinsic band gap (George et al., 2018; Huang et al., 2017; Dasgupta et al., 2017; Kim et al., 2016). In addition, these films are highly flexible and facilitate rapid charge transport in a vertical path. Consequently, MoS 2 can also be one of the talented ETM for stable PSCs if its work function can be controlled to a low enough value as compared to other ETMs such as SnO 2 and TiO 2 . The employment of MoS 2 thin films (composed of particulates) as an ETL in PSCs is limited to one report only (Singh et al., 2019). These typical MoS 2 thin films were mostly synthesized along the surface direction, with a few of them were grown vertically as produced via microwave irradiation method. These films are not applicable for the larger area production of PSCs because of their complex fabrication method and slower charge transport in the vertical direction. Also, the obtained power conversion efficiency (PCE) https://doi.org/10.1016/j.solener.2020.04.021 Received 25 January 2020; Received in revised form 6 April 2020; Accepted 8 April 2020 ⁎ Corresponding author. E-mail address: khalid@kaist.ac.kr (K. Mahmood). 1 Both authors contribute equally to this work. Solar Energy 203 (2020) 32–36 0038-092X/ © 2020 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. T