Carrier Diffusion Lengths in Hybrid Perovskites: Processing, Composition, Aging, and Surface Passivation Effects

Adhyaksa, Gede W. P.; Veldhuizen, L.W.; Kuang, Yinghuan; Brittman, Sarah; Schropp, R.E.I.; Garnett, Erik C.

doi:10.1021/acs.chemmater.6b00466

Cited by 122 publications

(127 citation statements)

References 33 publications

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“…Depending on processing technique, diffusion lengths in the range 200-500 nm have been observed for MAPbI 3 films which closely match typical film thicknesses seen in high efficiency MAPbI 3 devices. 53 However for devices that have used spray coating, optimal thin films cannot be produced yet and thicker films are generally obtained. Also in our case, reducing the film thickness further to o500 nm using spray technique proved difficult and produced extremely porous films exhibiting small rod like structures assumed to be PbI 2 (ESI †).…”

Section: 51mentioning

confidence: 99%

“…Depending on processing technique, diffusion lengths in the range 200-500 nm have been observed for MAPbI 3 films which closely match typical film thicknesses seen in high efficiency MAPbI 3 devices. 53 Therefore, in order to optimize the photo generated current from spray deposited MAPbI 3 films presented in this work, absorber thickness was reduced to around the same magnitude of carrier diffusion lengths. Decreasing the MAPbI 3 film thickness increased overall carrier collection as a substantial increase in PV performance at 0 minutes is observed for devices (Fig.…”

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confidence: 99%

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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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Section: 51mentioning

confidence: 99%

“…Depending on processing technique, diffusion lengths in the range 200-500 nm have been observed for MAPbI 3 films which closely match typical film thicknesses seen in high efficiency MAPbI 3 devices. 53 Therefore, in order to optimize the photo generated current from spray deposited MAPbI 3 films presented in this work, absorber thickness was reduced to around the same magnitude of carrier diffusion lengths. Decreasing the MAPbI 3 film thickness increased overall carrier collection as a substantial increase in PV performance at 0 minutes is observed for devices (Fig.…”

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confidence: 99%

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

et al. 2017

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“…The first observation of micron-scale carrier diffusion lengths in CH 3 NH 3 PbI 3−x Cl x 17-19 stimulated a comprehensive research effort aimed at understanding the nature of carrier transport. [20][21][22][23][24][25][26][27][28][29][30][31][32][33] Carrier mobilities and/or diffusion lengths have been studied using electrical techniques (e.g. AC Photo Hall, 25 spacecharge-limited current, 31 impedance spectroscopy, 21 , and spatially-resolved electron-beam-induced current 27 ) as well as optical techniques that rely on electrical contacts such as photoluminescence quenching 17,18 and scanning photocurrent microscopy.…”

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confidence: 99%

“…We note that a steady-state photocarrier grating method relying on a change of photocurrent induced by interference of continuous wave laser beams 47,48 was recently applied to organic-inorganic perovskite films. 32 In contrast to the approach used in Ref. 32, the transient grating technique applied in this work does not require electrical contacts to the sample and provides access to dynamic information about the photocarrier response.…”

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Carrier diffusion in thin-film CH3NH3PbI3 perovskite measured using four-wave mixing

Webber

Clegg

Mason

et al. 2017

Applied Physics Letters

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We report the application of femtosecond four-wave mixing (FWM) to the study of carrier transport in solution-processed CH3NH3PbI3. The diffusion coefficient was extracted through direct detection of the lateral diffusion of carriers utilizing the transient grating technique, coupled with simultaneous measurement of decay kinetics exploiting the versatility of the boxcar excitation beam geometry. The observation of exponential decay of the transient grating versus interpulse delay indicates diffusive transport with negligible trapping within the first nanosecond following excitation. The in-plane transport geometry in our experiments enabled the diffusion length to be compared directly with the grain size, indicating that carriers move across multiple grain boundaries prior to recombination. Our experiments illustrate the broad utility of FWM spectroscopy for rapid characterization of macroscopic film transport properties.Organo-lead trihalide perovskites possess a unique combination of electronic and optical properties, making them attractive for applications in light-emitting diodes, 1,2 lasers, 3-5 optical sensors, 6-8 and most notably high performance solar cells where the efficiencies have rapidly increased, reaching over 22% in just a few years. 9In addition, these hybrid perovskites can be solutionprocessed and applied as thin films to a variety of substrates, 10,11 pointing to the potential for large-scale, low-cost solar cell production.12-16 The transport properties of electrons and holes within the perovskite absorber material are crucial to the performance of photovoltaics and other optoelectronic technologies using these materials. The first observation of micron-scale carrier diffusion lengths in CH 3 NH 3 PbI 3−x Cl x 17-19 stimulated a comprehensive research effort aimed at understanding the nature of carrier transport.20-33 Carrier mobilities and/or diffusion lengths have been studied using electrical techniques (e.g. AC Photo Hall, 25 spacecharge-limited current, 31 impedance spectroscopy, 21 , and spatially-resolved electron-beam-induced current 27 ) as well as optical techniques that rely on electrical contacts such as photoluminescence quenching 17,18 and scanning photocurrent microscopy.26,33 Some of these techniques offer the ability to probe transport in a working solar cell device, however imperfectly characterized interface energetics and ambiguities tied to the model-dependent extraction of transport characteristics impede the determination of the physical processes limiting device performance.All-optical techniques provide an effective approach to studying carrier transport within a wide range of photovoltaic materials as no carrier extraction layers or ohmic contacts are required. Time-domain terahertz spectroscopy (TDTHz) and time-resolved microwave conductivity (TRMC) have provided valuable insight into carrier scattering processes in the organometal halide perovskites in recent years. 24,28,29 For such techniques, the quantitative determination of mobility requires modeling of the...

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Passivation Properties and Formation Mechanism of Amorphous Halide Perovskite Thin Films

Rigter

Quinn

Kumar

et al. 2021

Adv Funct Materials

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Lead halide perovskites are among the most exciting classes of optoelectronic materials due to their unique ability to form high‐quality crystals with tunable bandgaps in the visible and near‐infrared using simple solution precipitation reactions. This facile crystallization is driven by their ionic nature; just as with other salts, it is challenging to form amorphous halide perovskites, particularly in thin‐film form where they can most easily be studied. Here, rapid desolvation promoted by the addition of acetate precursors is shown as a general method for making amorphous lead halide perovskite films with a wide variety of compositions, including those using common organic cations (methylammonium and formamidinium) and anions (bromide and iodide). By controlling the amount of acetate, it is possible to tune from fully crystalline to fully amorphous films, with an interesting intermediate state consisting of crystalline islands embedded in an amorphous matrix. The amorphous lead halide perovskite has a large and tunable optical bandgap. It improves the photoluminescence quantum yield and lifetime of incorporated crystalline perovskite, opening up the intriguing possibility of using amorphous perovskite as a passivating contact, as is currently done in record efficiency silicon solar cells.

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Carrier Diffusion Lengths in Hybrid Perovskites: Processing, Composition, Aging, and Surface Passivation Effects

Cited by 122 publications

References 33 publications

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

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

Carrier diffusion in thin-film CH3NH3PbI3 perovskite measured using four-wave mixing

Passivation Properties and Formation Mechanism of Amorphous Halide Perovskite Thin Films

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Carrier Diffusion Lengths in Hybrid Perovskites: Processing, Composition, Aging, and Surface Passivation Effects

Cited by 122 publications

References 33 publications

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

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

Carrier diffusion in thin-film CH3NH3PbI3 perovskite measured using four-wave mixing

Passivation Properties and Formation Mechanism of Amorphous Halide Perovskite Thin Films

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

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