The Impact of the Crystallization Processes on the Structural and Optical Properties of Hybrid Perovskite Films for Photovoltaics.
We investigate the relationship between structural and optical properties of organo-lead mixed halide perovskite films as a function of the crystallization mechanism. For methylammonium lead tri-iodide, the organic cations rearrange within the inorganic cage, moving from crystals grown in a mesoporous scaffold to larger, oriented crystals grown on a flat substrate. This reduces the strain felt by the bonds forming the cage and affects the motion of the organic cation in it, influencing the electronic transition at the onset of the optical absorption spectrum of the semiconductor. Moreover, we demonstrate that in mixed-halide perovskite, though Cl(-) ions are not present in a detectable concentration in the unit cell, they drive the crystallization dynamics. This induces a preferential order during crystallization, from a molecular, i.e., organic-inorganic moieties arrangement, to a nano-mesoscopic level, i.e., larger crystals with anisotropic shape. Finally, we show that while Cl is mainly expelled from flat films made of large crystals, in the presence of an oxide mesoporous scaffold they are partially retained in the composite.
†Center for Nano Science and Technology @ Polimi, Istituto Italiano di Tecnologia, via Giovanni Pascoli 70/3, 20133, Milan, Italy.
Giulia
G
Grancini
‡Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego, 30, 16163 Genova, Italy.
Sergio
S
Marras
‡Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego, 30, 16163 Genova, Italy.
Mirko
M
Prato
§Institute of Crystallography, National Research Council, via Amendola 122/O, Bari 70126, Italy.
Cinzia
C
Giannini
∥Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, I-06123, Perugia, Italy.
Claudio
C
Quarti
∥Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, I-06123, Perugia, Italy.
Filippo
F
De Angelis
†Center for Nano Science and Technology @ Polimi, Istituto Italiano di Tecnologia, via Giovanni Pascoli 70/3, 20133, Milan, Italy.
Michele
M
De Bastiani
⊥Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, United Kingdom.
Giles E
GE
Eperon
⊥Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, United Kingdom.
Henry J
HJ
Snaith
‡Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego, 30, 16163 Genova, Italy.
Liberato
L
Manna
†Center for Nano Science and Technology @ Polimi, Istituto Italiano di Tecnologia, via Giovanni Pascoli 70/3, 20133, Milan, Italy.
Annamaria
A
Petrozza
EDS; Raman hybrid perovskite; SEM; XRD; chlorine doping; crystallization; flat junction; mesostructure; perovksite absorption; perovskite solar cell