Crystallization kinetics and morphology control of formamidinium-cesium mixed-cation lead mixed-halide perovskite via tunability of the colloidal precursor solution
David McMeekin a, Zhiping Wang a, Waqaas Rehman a, Federico Pulvirenti b, Jay Patel a, Nakita Noel a, Seth Marder b, Laura Herz a, Henry Snaith a
a University of Oxford, Department of Physics, Clarendon Laboratory, UK, Parks Road, United Kingdom
b Center for Organic Photonics and Electronics and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics 2018 (AP-HOPV18)
Kitakyūshū-shi, Japan, 2018 January 28th - 30th
Organizers: Shuzi Hayase, Juan Bisquert and Hiroshi Segawa
Oral, David McMeekin, presentation 037
DOI: https://doi.org/10.29363/nanoge.ap-hopv.2018.037
Publication date: 27th October 2017

Title: Crystallization kinetics and morphology control of formamidinium-cesium mixed-cation lead mixed-halide perovskite via tunability of the colloidal precursor solution

David P. McMeekin,1 Zhiping Wang,1 Waqaas Rehman,1 Federico Pulvirenti,2 Jay B. Patel,1 Nakita K. Noel,1 Michael B. Johnston,1 Seth R. Marder,2 Laura M. Herz,1 Henry J. Snaith1*

1 Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK

2 School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA 30332-0400

* Corresponding author E-mail: henry.snaith@physics.ox.ac.uk

 

The meteoric rise of the field of perovskite solar cells has been fueled by the ease with which a wide range of high-quality materials can be fabricated via simple solution processing methods. However, to date, little effort has been devoted to understanding the precursor solutions, and the role of additives such as hydrohalic acids upon film crystallization and final optoelectronic quality. Here, a direct link between the colloids concentration present in the [HC(NH2)2]0.83Cs0.17Pb(Br0.2I0.8)3 precursor solution and the nucleation and growth stages of the thin film formation is established. Using dynamic light scattering analysis, the dissolution of colloids over a time span triggered by the addition of hydrohalic acids is monitored. These colloids appear to provide nucleation sites for the perovskite crystallization, which critically impacts morphology, crystal quality, and optoelectronic properties. Via 2D X-ray diffraction, highly ordered and textured crystals for films prepared from solutions with lower colloidal concentrations are observed. This increase in material quality allows for a reduction in microstrain along with a twofold increase in charge-carrier mobilities leading to values exceeding 20 cm2 V−1 s−1. Using a solution with an optimized colloidal concentration, devices that reach current–voltage measured power conversion efficiency of 18.8% and stabilized efficiency of 17.9% are fabricated.

 

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