Influence of Environment and Light-Stress on the Optoelectronic Properties of Triple-Cation Perovskite Thin Films

Lin, Huai-San; Cacovich, Stéfania; Rebai, Amelle; Rousset, Jean; Longeaud, Christophe

doi:10.1021/acsami.0c01732

Cited by 16 publications

(15 citation statements)

References 34 publications

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“…The slope of this linear behavior gives a direct access to the product αk 2 . The absorption coefficient can be measured via other methods such as Fourier transform photocurrent spectroscopy [42,43] or ellipsometry [44]. Therefore, one can extract a direct measurement of the external radiative recombination rate k 2 .…”

Section: A the Drift-diffusion Modelmentioning

confidence: 99%

Mapping Transport Properties of Halide Perovskites via Short-Time-Dynamics Scaling Laws and Subnanosecond-Time-Resolution Imaging

et al. 2021

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The excellent optoelectronic and transport properties of halide perovskites led to a rapid development of perovskite based optoelectronic devices. The fundamental understanding of charge carrier dynamics as well as the implementation of physical models able to accurately describe their behaviour are essential for further improvements in the field. Here, combining advanced modeling and characterization, a method for analyzing the short time dynamics of time resolved fluorescence imaging (TR-FLIM) decays is demonstrated. A theoretical scaling law for the time derivative of transient photoluminescence decays as a function of the excitation power is extracted. This scaling law, computed from classical drift-diffusion equations, defines an innovative and simple way to extract quantitative values for several transport parameters including the external radiative recombination coefficient. The model was notably applied on a set of images acquired with a temporal shift of 250 ps to map the top surface recombination velocity of a triple cation mixed halide perovskite thin film at the microscale. The development of high-time-resolution imaging techniques coupled with the scaling method for analyzing short-time dynamics provides a solid platform for the investigation of local heterogeneities in semiconductor materials and the accurate determination of the main parameters governing their carrier transport. I. INTRODUCTIONOver the last decade, lead-halide perovskites solar cells have proved to be a serious candidate for reaching large scale photovoltaic (PV) solar energy conversion, a much-needed solution to meet climate targets and move towards a low-carbon economy. However, despite this emerging technology has recently reached a record power conversion efficiency of 25.5% for a single junction device [1,2], several open questions persist in the scientific community, ranging from the nature and densities of the defects in the absorbers [3-5], the optimal design for the interfaces energetics in a full device [6,7], and the long term stability [7][8][9].The optimization of device performances goes along with the complete understanding of complex recombination processes occurring both in the bulk and at the interfaces. Due to the interplay of several chemical and physical parameters in these hybrid compounds, such

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Section: A the Drift-diffusion Modelmentioning

confidence: 99%

Mapping Transport Properties of Halide Perovskites via Short-Time-Dynamics Scaling Laws and Subnanosecond-Time-Resolution Imaging

et al. 2021

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“…[13][14][15] Unlike in Si or CdTe, HPs break down due to chemical reactions of the semiconductor with water, oxygen, and photoexcited electrons, 6,[16][17][18][19][20] and there exists a strong correlation between decay of optoelectronic properties such as carrier diffusion length and material transformation rate. 21,22 In oxygen and light, a photooxidationinduced degradation of MAPbI3 has been reported previously 19,23,24 and is widely believed to occur via a mechanism that involves superoxide radical (𝑂 2…”

Section: Introductionmentioning

confidence: 97%

Water-Accelerated Photo-oxidation of CH3NH3PbI3 Perovskite: Mechanism, rate orders, and rate constants

Siegler

Dunlap-Shohl

Meng

et al. 2021

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Understanding the chemical reactions that hybrid organic-inorganic halide perovskite (HP) semiconductors undergo in the presence of moisture, oxygen, and light are essential to the commercial development of HP solar cells and optoelectronics. Here we use optical absorbance to study the kinetics of methylammonium lead iodide (MAPbI3) degradation in response to combinations of moisture, oxygen, and illumination over a range of temperatures. We identify two primary reaction pathways that dominate MAPbI3 material degradation in these mixed environmental conditions: (1) dry photooxidation (DPO) due to the combined role of oxygen and photoexcited electrons (with a rate of 2 x 10-9 mol/m2∙s in dry air at 25 C and an effective activation energy of 0.62 eV), and (2) a water-accelerated photooxidation (WPO) process due to the combined role of water, oxygen, and photoexcited electrons (with a rate of 1 x 10-7 mol/m2s in 50% RH air at 25 C and observed effective activation energy of 0.07 eV). Commonly reported humidity-only, blue light, and thermal degradation pathways are demonstrated to have rates that are respectively 100, 1000, and >1000 times slower than predominant photooxidation processes in ambient conditions. Extracting kinetic rate constants from the dynamics of the initial degradation, we calculate that in dry air, photooxidation rate of MAPbI3 follows a f(x)∝x/(1+Kx) relationship with respect to oxygen in the vapor phase (PO2) and excess concentration of photoexcited electrons (n). In humid air, photooxidation of MAPbI3 exhibits first order kinetics with respect to the partial pressure of water in the vapor phase (PH2O). However, with respect to PO2 and n, kinetics follow a f(x)∝x/(1+kx)^2 relationship with respect to rate. We then identify a plausible reaction mechanism for degradation of MAPbI3 material that is consistent with these rate functionalities. The rate determining step for both DPO and WPO is proton abstraction by photogenerated superoxide radicals. However, proton donation by adsorbed water proceeds much more rapidly than donation by methylammonium, resulting in faster degradation rates for WPO at typical ambient conditions (~50% RH). Rate laws derived from this mechanism were fit to the entire dataset to extract rate constants for DPO and WPO processes. Accurate predictions of material degradation rates, with narrow confidence intervals of fit parameters as identified by the Bootstrap algorithm, provide the first experimental estimates of the equilibrium constants of oxygen adsorption on MAPbI3 (Keq ≈ 3 x 10-3 kPa-1) and superoxide generation from adsorbed oxygen and photoexcited electrons in MAPbI3 (Keq ≈ 5 x 10-15 (photons/m2∙s)-0.7). Given that water has been reported as a degradation product of DPO, the results reported here highlight the need for the development of encapsulation schemes that rigorously block oxygen, as over longer time periods, product water (if generated) may accumulate inside the packaging and initiate the much faster WPO process.

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“…[13][14][15] Unlike in Si or CdTe, HPs degrade due to chemical reactions of the semiconductor with water, oxygen, and photoexcited electrons, 6,[16][17][18][19][20] and there exists a strong correlation between decay of optoelectronic properties such as carrier diffusion length and material transformation rate. 21,22 In oxygen and light, a photooxidationinduced degradation of MAPbI3 has been reported previously 19,23,24 and is widely believed to occur via a mechanism that involves superoxide radical (𝑂 2…”

Section: Introductionmentioning

confidence: 97%

Water-Accelerated Photo-oxidation of CH3NH3PbI3 Perovskite: Mechanism, rate orders, and rate constants

Siegler

Dunlap-Shohl

Meng

et al. 2021

Preprint

View full text Add to dashboard Cite

Optical absorbance is used to study the kinetics of methylammonium lead iodide (MAPbI3) thin film degradation in response to combinations of moisture, oxygen, and illumination over a range of temperatures. 105 degradations were conducted over 41 unique environmental conditions. We discover that water acts synergistically with oxygen in a water-accelerated photo-oxidation (WPO) pathway. This pathway is the dominant pathway at 25 °C and is 10, 100, 1000, and >1000 times faster than dry photooxidation (DPO), degradation via hydrate formation, thermal degradation, and blue light degradation, respectively. We find that the rate determining step for DPO is proton abstraction from methylammonium while for WPO it is proton abstraction from water, which occurs at a faster rate and results in water acting as an accelerant for photooxidation of MAPbI3. A full kinetic rate equation is derived and fitted to the data to determine activation energies and rate constants.

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Influence of Environment and Light-Stress on the Optoelectronic Properties of Triple-Cation Perovskite Thin Films

Cited by 16 publications

References 34 publications

Mapping Transport Properties of Halide Perovskites via Short-Time-Dynamics Scaling Laws and Subnanosecond-Time-Resolution Imaging

Mapping Transport Properties of Halide Perovskites via Short-Time-Dynamics Scaling Laws and Subnanosecond-Time-Resolution Imaging

Water-Accelerated Photo-oxidation of CH3NH3PbI3 Perovskite: Mechanism, rate orders, and rate constants

Water-Accelerated Photo-oxidation of CH3NH3PbI3 Perovskite: Mechanism, rate orders, and rate constants

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