TY - JOUR
T1 - Time-resolved imaging of carrier transport in halide perovskite thin films and evidence for nondiffusive transport
AU - Sridharan, Aravindan
AU - Noel, Nakita K.
AU - Hwang, Hyeon
AU - Hafezian, Soroush
AU - Rand, Barry P.
AU - Kéna-Cohen, Stéphane
N1 - Funding Information:
S.K.-C. acknowledges support from the Natural Sciences and Engineering Research Council of Canada and the Canada Research Chair in Hybrid and Molecular Photonics. A.S. acknowledges support from NSERC PGS-D as well as Institut d’Énergie Trottier (IET) grant programs. N.K.N. acknowledges funding via a fellowship from the Princeton Center for Complex Materials (PCCM). B.P.R. acknowledges support from the Office of Naval Research (ONR) Young Investigator Program (Award No. N00014-17-1-2005).
Publisher Copyright:
© 2019 American Physical Society.
PY - 2019/12/16
Y1 - 2019/12/16
N2 - Owing to their exceptional semiconducting properties, hybrid inorganic-organic perovskites show great promise as photovoltaic absorbers. In these materials, long-range diffusion of charge carriers allows for most of the photogenerated carriers to contribute to the photovoltaic efficiency. Here, time-resolved photoluminescence (PL) microscopy is used to directly probe ambipolar carrier diffusion and recombination kinetics in hybrid perovskites. This technique is applied to thin films of methylammonium lead tri-iodide (MAPbI3) obtained with two different fabrication routes, methylammonium lead tribromide (MAPbBr3), and an alloy of formamidinium lead tri-iodide and methylammonium lead bromide FA0.85MA0.15Pb(I0.85Br0.15)3. Average diffusion coefficients in the films leading to the highest device efficiencies and longest lifetimes, i.e., in FA0.85MA0.15Pb(I0.85Br0.15)3 and acetonitrile-processed MAPbI3, are found to be several orders of magnitude lower than in the other films. Further examination of the time dependence shows strong evidence for nondiffusive transport. In particular, acetonitrile-processed MAPbI3 shows distinct diffusion regimes on short and long timescales with an effective diffusion constant varying over 2 orders of magnitude. Our results also highlight the fact that increases in carrier lifetime in this class of materials are not necessarily concomitant with increased diffusion lengths and that the PL quantum efficiency under solar cell operating conditions is a greater indication of material, and ultimately device, quality.
AB - Owing to their exceptional semiconducting properties, hybrid inorganic-organic perovskites show great promise as photovoltaic absorbers. In these materials, long-range diffusion of charge carriers allows for most of the photogenerated carriers to contribute to the photovoltaic efficiency. Here, time-resolved photoluminescence (PL) microscopy is used to directly probe ambipolar carrier diffusion and recombination kinetics in hybrid perovskites. This technique is applied to thin films of methylammonium lead tri-iodide (MAPbI3) obtained with two different fabrication routes, methylammonium lead tribromide (MAPbBr3), and an alloy of formamidinium lead tri-iodide and methylammonium lead bromide FA0.85MA0.15Pb(I0.85Br0.15)3. Average diffusion coefficients in the films leading to the highest device efficiencies and longest lifetimes, i.e., in FA0.85MA0.15Pb(I0.85Br0.15)3 and acetonitrile-processed MAPbI3, are found to be several orders of magnitude lower than in the other films. Further examination of the time dependence shows strong evidence for nondiffusive transport. In particular, acetonitrile-processed MAPbI3 shows distinct diffusion regimes on short and long timescales with an effective diffusion constant varying over 2 orders of magnitude. Our results also highlight the fact that increases in carrier lifetime in this class of materials are not necessarily concomitant with increased diffusion lengths and that the PL quantum efficiency under solar cell operating conditions is a greater indication of material, and ultimately device, quality.
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U2 - 10.1103/PhysRevMaterials.3.125403
DO - 10.1103/PhysRevMaterials.3.125403
M3 - Article
AN - SCOPUS:85077361012
SN - 2475-9953
VL - 3
JO - Physical Review Materials
JF - Physical Review Materials
IS - 12
M1 - 125403
ER -