Scalable Route to the Fabrication of CH₃NH₃PbI₃ Perovskite Thin Films by Electrodeposition and Vapor Conversion

Abstract

Hybrid halide perovskite thin films are applicable in a wide range of devices such as light-emitting diodes, solar cells, and photodetectors. The optoelectronic properties of perovskites together with their simple and inexpensive film deposition methods make these materials a viable alternative to established materials in these devices. However, the potential of perovskite materials is compromised by the limitations of the existing deposition methods, which suffer from trade-off among suitability for large-scale industrial production in a batch or roll-to-roll manner, deposition area, film quality, and costs. We addressed these limitations by developing a deposition method that is inexpensive, applicable to large substrate areas, scalable, and yields high-quality perovskite films. In this study, the low-cost electrodeposition (ED) method and sequential exposure to reagent vapors produce CH 3 NH 3 PbI 3 perovskite films with thickness nonuniformity below 9% on a centimeter scale. PbO 2 films are electrodeposited first and then undergo two vapor conversion steps, with HI vapor in the first step and CH 3 NH 3 I vapor in the second step. The second step yields CH 3 NH 3 PbI 3 films that are continuous and consist of micrometer-sized grains. This process allows the preparation of both α- and β-phase CH 3 NH 3 PbI 3 films, offers a simple means to control the film thickness, and works over a wide range of film thicknesses. In this work, films with thicknesses ranging from 100 nm to 10 μm were prepared. ED and vapor conversion are inherently scalable techniques and hence the process described herein could benefit application areas in which large device areas and throughput are required, such as the production of solar cells.

Electrochemically Assisted Growth of CsPbBr3‐Based Solar Cells Without Selective Contacts

“…Figure 2 shows the different stages in CsPbBr 3 formation from bare FTO. In contrast to a previous study, [48] where well-covered films were obtained only after 500 s, we accomplished a very homogeneous and well-covering PbO 2 film after 280 s of reaction with the same current density. This is probably due to the positive effect of the activation protocol with HNO 3 on the FTO pieces before electrodeposition.…”

“…(1)], galvanostatic electrodeposition of PbO 2 over FTO has proven useful to prepare MAPI. After PbO 2 films were formed and characterized, their conversion to PbBr 2 was designed in a similar way as reported by Kemel et al [48] They reported for the first time the chemical reduction of PbO 2 films to PbI 2 under exposure to HI vapors.…”

“…A lead-based electrolyte was prepared following the methodology reported. [48] Na(C 2 H 3 O 2 ) 2 × 3H 2 O was dissolved in 40 mL of water, and then the pH value was adjusted to 5.5 with glacial acetic acid. Separately, PbC 2 H 3 O 2 × 3H 2 O was also dissolved in 40 mL of deionized water and added slowly to the sodium acetate solution.…”

“…[39,40] This less explored method includes the electrochemical deposition of a lead precursor such as PbI 2 , [41] PbO [42][43][44][45] or PbO 2 . [46][47][48] MAPI-based PSCs have exhibited best power conversion efficiencies (PCE) of 14.59 % and 10.19 % for PbO and PbO 2 precursors, respectively. [43] Particularly, PbO 2 has a widely accepted electrochemical formation mechanism via anodic reaction of Pb(II) either in acidic or alkaline conditions.…”

“…PbI 2 is further converted into the final MAPI film by reaction with CH 3 NH 3 I dissolved in isopropanol. [47,48] In this work, we make use of the electrochemical deposition technique as an alternative to spin-coating to control the lead transfer from precursors towards a substrate for further CsPbBr 3 deposition. As a novel strategy we have used very little amounts of hot HBr in a closed rounded glass flask which reacted with an electrodeposited PbO 2 film to obtain an intermediate PbBr 2 film.…”