In Situ Investigation and Photovoltaic Devices: Sequential Formation of Tunable-Bandgap Mixed-Halide Lead-based Perovskites
Dounya Barrit a b, Yalan Zhang c, Ming-Chun Tang a, Ruipeng Li d, Detlef-M. Smilgies e, Shengzhong (Frank) Liu c, Thomas D. Anthopoulos a, Aram Amassian f, Kui Zhao c
a King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
b Research Institute for Solar Energy and New Energies, Green Energy Park, Morocco, Green Energy Park, km2 R206, Benguerir, Maroc, Benguerir, Morocco
c Shaanxi Normal University, Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Key Laboratory for Advanced Energy Devices; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Xi’an, China., Chang'an, Xi'an, China, 710119, Xi'an, China
d Brookhaven National Laboratory, Chemistry Department, Upton, NY, USA, 11973, United States
e Cornell University, Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory Ithaca, NY 14853, USA, Ithaca, United States
f North Carolina State University (NCSU), Department of Materials Science and Engineering, Raleigh, Raleigh, Carolina del Norte 27695, EE. UU., Raleigh, United States
Proceedings of Online School on Hybrid, Organic and Perovskite Photovoltaics (HOPE-PV)
Online, Spain, 2020 November 3rd - 13th
Organizers: Sergey M. Aldoshin, Jovana Milic, Keith Stevenson and Pavel Troshin
Oral, Dounya Barrit, presentation 018
Publication date: 23rd October 2020

Inorganic−organic hybrid perovskite films of MAPb(IxBr1-x)3 (0 ˂ x ˂ 1)  represents a path for efficient multi-junction or tandem solar cells due to their tunable bandgap (1.60-2.24 eV). Here, sequential solution deposition is adapted to enable a direct observation and a full understanding of the phase transformation from Pb(IxBr1-x)2 precursors to perovskites. This method has been successfully applied toward the fabrication of homogenous perovskite layers allowing an improvement of optoelectronic properties and device performance. In situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) measurements are performed to present a detailed view of the effects of solvent, lead halide film solvation, and Br incorporation and alloying on the transformation behavior. Supported by other techniques such as in situ optical reflectance, absorption, x-ray diffraction, and steady-state/time-resolved photoluminescence, the measurements indicate a strong tendency of lead halide solvation prior to crystallization during solution-casting Pb(IxBr1-x)2 precursor from a dimethyl sulfoxide (DMSO) solvent with the Br alloying leading to weakened solvation of Pb(IxBr1-x)2×DMSO. We demonstrate a room temperature conversion of perovskite and high-quality films with tunable bandgap reaching a higher power conversion efficiency of 16.42% based on MAPb(I0.9Br0.1)3 due to highly efficient intramolecular exchange between DMSO molecules and organic cations. These findings highlight the benefits that solvation of the precursor phases, together with bromide incorporation can have on the microstructure, morphology and optoelectronic properties of these films, providing a viable alternative approach to one-step synthesis approach used for mixed ion perovskite thin films.

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