Single‐Source Vapor‐Deposition of MA_1–xFA_xPbI₃ Perovskite Absorbers for Solar Cells

Abstract

Vapor deposition of halide perovskites presents high potential for scalability and industrial processing of perovskite solar cells. It prevents the use of toxic solvents, allows thickness control, and yields conformal and uniform coating over large areas. However, the distinct volatility of the perovskite organic and inorganic components currently requires the use of multiple thermal sources or two‐step deposition to achieve the perovskite phase. In this work, single‐source, single‐step MA1–xFAxPbI3 thin film deposition with tunable stoichiometry by pulsed laser deposition is demostrated. By controlling the laser ablation of a solid target containing adjustable MAI:FAI:PbI2 ratios, the room temperature formation of cubic α‐phase MA1–xFAxPbI3 thin films is demonstrated. The target‐to‐film transfer of the ablated species, including the integrity of the organic molecules and the desired MA+:FA+ ratio, is confirmed by x‐ray photoelectron spectroscopy and solid‐state NMR. Photoluminescence analysis further confirms the shift of the bandgap with varying the MA+:FA+ ratio. Finally, proof‐of‐concept n‐i‐p solar cells with 14% efficiency are demonstrated with as‐deposited non‐passivated pulsed laser deposition (PLD)‐MA1–xFAxPbI3. This study opens the path for future developments in industry‐compatible vapor‐deposition methods for perovskite solar cells.

Vapor phase deposition of perovskite photovoltaics: short track to commercialization?

“…This might also limit the chance of success for single-source approaches in which organic and inorganic compounds are deposited from just one source, given the inevitable decomposition of the organic halides at the elevated temperatures required to simultaneously deposit the inorganic compounds. While alternative single-source techniques such as laser deposition or sputtering were proposed, 44,82,83 they were not able to fully leave the “comfort zone” either because of lower performance or only limited improvements in deposition speed and proof of their suitability in an industrial setting is yet to be demonstrated. Classical multi-source co-evaporation approaches, which are the most successful approaches when it comes to versatility and performance on a laboratory scale, do not offer much room for improvements either (other than geometrical source considerations discussed before), as they are similarly limited by the maximum accessible deposition rate of the organic compounds.…”

Single-Source Pulsed Laser Deposited Perovskite Solar Cells with >19% Efficiency

“…11 The mol ratio of the organic components MAI: FAI was chosen as 75:25 as optimized in a previous work. 12 The PbCl 2 content in the target was varied from 0-50 mol% with respect to PbI as received, were transferred to zirconia-coated vials containing zirconia beds and mixed using a housebuilt rotatory ball miller. Subsequently, the mixed powders were uniaxially pressed at RT, employing 470 MPa into a ≈ 2.5 mm thick disc of 20 mm in diameter.…”

“…The calibration of target composition vs nal lm composition has been described in detail in our earlier work. 12 The morphology of the thin lms is shown in Fig. 1e, revealing a predominantly compact columnar growth from the rst 20 nm onwards.…”

Incremental Feeding of Perovskite Powders: Angstrom‐Precision Growth for Single‐Source Solar Cell Fabrication

“…Similarly, Tai et al [ 33 ] used a laser‐induced flash‐evaporation process yielding 16.8% efficient devices and parallel advances in pulsed laser deposition reported 14% efficient devices with a MA x FA 1− x PbI 3 composition, demonstrating the transfer of multiple organic cations as a single‐source. [ 34,35 ] However, the lasers involved in such deposition systems can be cost‐prohibitive for deployment in large‐scale, such as those needed for PV.…”