CH3NH3PbI3 perovskite single crystals: surface photophysics and their interaction with the environment

Grancini, Giulia; D’Innocenzo, Valerio; Dohner, Emma R.; Martino, Nicola; Kandada, Ajay Ram Srimath; Mosconi, Edoardo; Angelis, Filippo De; Karunadasa, Hemamala I.; Hoke, Eric T.; Petrozza, Annamaria

doi:10.1039/c5sc02542g

Cited by 195 publications

(214 citation statements)

References 30 publications

(73 reference statements)

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“…[30,31] The larger bandgap at the SC surface could be due to the strong lattice deformation arising from lattice strain at the surface and for TF. [22,31] The PL decay lifetimes of the surface and the bulk are also significantly different. Under low fluence, 800 nm excitation (2PA) leads to a monomolecular decay.…”

Section: Introductionmentioning

confidence: 97%

Discerning the Surface and Bulk Recombination Kinetics of Organic–Inorganic Halide Perovskite Single Crystals

Nguyen

et al. 2016

Advanced Energy Materials

286

336

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Organic–inorganic halide perovskite single crystals possess many outstanding properties conducive for photovoltaic and optoelectronic applications. However, a clear photophysics picture is still elusive, particularly, their surface and bulk photophysics are inexorably convoluted by the spectral absorbance, defects, coexisting photoexcited species, etc. In this work, an all‐optical study is presented that clearly distinguishes the surface kinetics from those of the bulk in the representative methylammonium‐lead bromide (MAPbBr3) and ‐lead iodide (MAPbI3) single crystals. It is found that the bulk recombination lifetime of the MAPbBr3 single crystal is shortened significantly by approximately one to two orders (i.e., from ≈34 to ≈1 ns) at the surface with a surface recombination velocity of around 6.7 × 103 cm s−1. The surface trap density is estimated to be around 6.0 × 1017 cm−3, which is two orders larger than that of the bulk (5.8 × 1015 cm−3). Correspondingly, the diffusion length of the surface excited species is ≈130–160 nm, which is considerably reduced compared to the bulk value of ≈2.6–4.3 μm. Furthermore, the surface region has a wider bandgap that possibly arises from the strong lattice deformation. The findings provide new insights into the intrinsic photophysics essential for single crystal perovskite photovoltaics and optoelectronic devices.

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Section: Introductionmentioning

confidence: 97%

Discerning the Surface and Bulk Recombination Kinetics of Organic–Inorganic Halide Perovskite Single Crystals

Nguyen

et al. 2016

Advanced Energy Materials

286

336

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“…21. Only very recently, Grancini et al have published a fundamental work on the vibrational modes of MAPbI 3 single crystals observing two very broad bands at approximately 110 cm −1 and 250 cm −1 39.…”

mentioning

confidence: 99%

Advanced Raman Spectroscopy of Methylammonium Lead Iodide: Development of a Non-destructive Characterisation Methodology

Pistor

Ruiz

Cabot

et al. 2016

Sci Rep

115

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In recent years, there has been an impressively fast technological progress in the development of highly efficient lead halide perovskite solar cells. However, the stability of perovskite films and respective solar cells is still an open point of concern and calls for advanced characterization methods. In this work, we identify appropriate measurement conditions for a meaningful analysis of spin-coated absorber-grade perovskite thin films based on methylammonium (MA) lead iodide (MAPbI3) by Raman spectroscopy. The material under investigation and its derivates is the most commonly used for high efficiency devices in the literatures and has yielded working solar cell devices with efficiencies around 10% in our laboratory. We report highly detailed Raman spectra obtained with excitation at 532 nm and 633 nm and their deconvolution taking advantage of the simultaneous fitting of spectra obtained with varying excitation wavelengths. Finally, we propose a fast and contactless methodology based on Raman to probe composition variations and/or degradation of these perovskite thin films and discuss the potential of the presented technique as quality control and degradation monitoring tool in other organic-inorganic perovskite materials and complete solar cell devices.

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“…MAI can be further broken down to CH 3 NH 2 (liquid) and HI (liquid) with the latter easily reacting with O 2 to form I 2 (solid) and H 2 O (liquid) or decompose into I 2 (solid) and H 2 (gas). 24 In this work we use a low costing and scalable one-step spray technique to fabricate solution processed MAPbI 3 films. By changing the concentration of MAPbI 3 in DMF solution (0.25 M and 0.125 M) along with the spray volume (400 mL, 300 mL and 200 mL) we were able to control the film thickness.…”

Section: Introductionmentioning

confidence: 99%

Understanding surface chemistry during MAPbI₃ spray deposition and its effect on photovoltaic performance

et al. 2017

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aIn recent years there has been significant research into organic-inorganic halide perovskites for photovoltaic applications and has resulted in power conversion efficiencies greater than 20%. A number of deposition techniques have been utilized to produce high quality perovskite films including thermal evaporation, single and two-step spin coating and vapor assisted processes. However, these laboratory based fabrication methods are not well matched with low costing, roll to roll processing that is associated with large scale manufacture. In this work we use a low costing and rapid spray coating technique to fabricate solution processed MAPbI 3 films with controlled film thickness achieved through modifying concentration/spray volume. Investigation into the chemical composition and film morphology showed differing surface chemistries for the different film thicknesses, altering the surface morphology from large micro grained structures to small distorted grain arrangements. We have then implemented spray deposited films into solar devices (ITO/TiO 2 /MAPbI 3 /Au) and have studied the current density-voltage (JV) characteristics including light soaking effects. Through optimizing the absorber thickness the short-circuit current density is increased from 4.9 mA cm À2 to 22.3 mA cm À2, increasing overall power conversion efficiency by a factor 45. Investigation into the performance of devices under continued illumination showed an inverse relationship existed between low efficiency (thick) MAPbI 3 films and high efficiency (thin) MAPbI 3 films, where the former displayed large increases in overall performance compared to the rapid degradation in the latter. We attribute device instabilities to the increase in defect density as a consequence of the spray-induced surface chemistry, leading to trap assisted recombination at the back electrode.

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CH₃NH₃PbI₃ perovskite single crystals: surface photophysics and their interaction with the environment

Abstract: Structural inhomogeneity on a micrometer-scale across a CH3NH3PbI3 single crystal is responsible for a local modulation of the optical band gap, which is also highly sensitive to humidity.

Cited by 195 publications

References 30 publications

Discerning the Surface and Bulk Recombination Kinetics of Organic–Inorganic Halide Perovskite Single Crystals

Discerning the Surface and Bulk Recombination Kinetics of Organic–Inorganic Halide Perovskite Single Crystals

Advanced Raman Spectroscopy of Methylammonium Lead Iodide: Development of a Non-destructive Characterisation Methodology

Understanding surface chemistry during MAPbI₃ spray deposition and its effect on photovoltaic performance

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CH3NH3PbI3 perovskite single crystals: surface photophysics and their interaction with the environment

Abstract: Structural inhomogeneity on a micrometer-scale across a CH3NH3PbI3 single crystal is responsible for a local modulation of the optical band gap, which is also highly sensitive to humidity.

Cited by 195 publications

References 30 publications

Discerning the Surface and Bulk Recombination Kinetics of Organic–Inorganic Halide Perovskite Single Crystals

Discerning the Surface and Bulk Recombination Kinetics of Organic–Inorganic Halide Perovskite Single Crystals

Advanced Raman Spectroscopy of Methylammonium Lead Iodide: Development of a Non-destructive Characterisation Methodology

Understanding surface chemistry during MAPbI3 spray deposition and its effect on photovoltaic performance

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Product

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CH₃NH₃PbI₃ perovskite single crystals: surface photophysics and their interaction with the environment

Understanding surface chemistry during MAPbI₃ spray deposition and its effect on photovoltaic performance