Metal oxide sol annealing on perovskite MAPbI(3) film with thermal stability enhanced by caffeine additive and PMMA interlayer

Soo, Yew Hang and Ng, Chai Yan and Jun, Hieng Kiat and Ng, Soo Ai and Wong, Yew Hoong (2022) Metal oxide sol annealing on perovskite MAPbI(3) film with thermal stability enhanced by caffeine additive and PMMA interlayer. Journal of Materials Science, 57 (22, SI). pp. 10242-10259. ISSN 0022-2461, DOI

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Methylammonium lead iodide (MAPbI(3)) is a popular light-absorbing layer in the perovskite solar cells (PSCs). However, the poor thermal stability of MAPbI(3) has inhibited the direct annealing of low-temperature processed (<= 150 degrees C) metal oxide sols as a charge transport layer (CTL) on top of it. In this work, caffeine as a nonvolatile and low-cost additive was added into the poly(methyl methacrylate) (PMMA)-encapsulated MAPbI(3) film to enhance its thermal stability at 150 degrees C. The caffeine-added MAPbI(3) (C-MAPbI(3)) film was prepared using antisolvent-assisted one-step spin-coating. With caffeine additive, the thermal degradation of the C-MAPbI(3) film was significantly reduced, and the film still retained dominating MAPbI(3) phase after 24 h of annealing. In addition, the caffeine additive improved the film morphology by promoting seamless grain boundary formation. The thickness of the PMMA encapsulation layer deposited on top of the C-MAPbI(3) film could be reduced from similar to 1550 nm (charge insulating layer) to similar to 60 nm (ultrathin charge tunneling layer) without sacrificing the thermal stability of the C-MAPbI(3) film. The vanadium oxide (VOx) sol was spin-coated on the similar to 60 nm PMMA-encapsulated C-MAPbI(3) film and annealed at 150 degrees C for 20 min to act as a hole transport layer (HTL). The VOx sol could be annealed without causing thermal degradation to the C-MAPbI(3) film. With this discovery, the VOx may replace the thermally unstable organic HTLs in n-i-p PSCs. This low-cost and facile metal oxide sol route would lead to economic and scalable production of all-metal oxide CTL-based PSCs with significantly improved device operational stability.

Item Type: Article
Funders: Universiti Tunku Abdul Rahman [Grant No:UTARRF/2020-C2/N02]
Uncontrolled Keywords: Materials science, Multidisciplinary
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Engineering > Department of Mechanical Engineering
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 11 Oct 2023 06:41
Last Modified: 11 Oct 2023 06:41

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