PbI2 and Lead Halide Perovskites by Atomic Layer Deposition for Perovskite Solar Cells
Jacob Vagott a, Carlo Perini a, Andres Felipe Castro Mendez a, Juanita Hidalgo a, Kathryn Bairley a, Juan-Pablo Correa-Baena a
a School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Jacob Vagott, presentation 138
DOI: https://doi.org/10.29363/nanoge.hopv.2022.138
Publication date: 20th April 2022

Hybrid organic—inorganic lead halide perovskites (LHPs) have risen to prominence since 2009 as an absorber layer in high efficiency solar cells due to their optimal bandgaps, absorption characteristics, and carrier transport properties. LHPs have been used to achieve 25.5% maximum power conversion efficiency (PCE) single-junction solar cells. So far, the highest efficiency perovskite solar cells (PSCs) have involved the use of spin-coating for deposition of the perovskite layer. Drawbacks of this solution deposition method include the use of toxic solvents, limited deposition area, and lack of fine control over the deposition process. By achieving atomic control of perovskite deposition, it also unlocks the capability to deposit ultrathin passivation layers for defect mitigation in solar cells and other optoelectronic applications. Atomic layer deposition (ALD) is a vapor deposition process that allows for angstrom-level thickness control through self-limiting reactions. Compatible with roll-to-roll manufacturing, ALD allows for deposition of highly conformal films over much larger areas than are currently possible via solution processing. However, there is little understanding of the processes of formation of LHPs by ALD. It may be considered that the process must be a combination of self-limiting ALD processes, where a lead halide (i.e. PbI2) film is first deposited before being converted to perovskite through a separate process involving the deposition of an organic halide such as methylammonium iodide (MAI). Stoichiometry can be finely tuned once the individual processes have been developed by varying the number of lead halide to organic halide layers. Our work so far has focused on depositing PbI2 has laid a foundation to build upon in order to achieve deposition of lead halide perovskites by atomic layer deposition. At low temperatures, conformal and reliable PbI2 thin films are able to be deposited, while at temperatures above 100ºC, nanocrystalline growth is observed. 

This work was performed in part at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (Grant ECCS1542174). J.N.V. acknowledges the Georgia Tech Graduate Assistance in Areas of National Need (GAANN) fellowship for career funding. J.N.V. was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate (NDSEG) Fellowship Program. J.-P.C.- B. and J.N.V. acknowledge Jamie Wooding and Dr. Mark Losego for their assistance with AFM measurements and analysis. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02- 06CH11357. J.-P.C.-B. and his group are supported by the Micron Foundation and Goizueta Foundation.

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