Real-space observation of unbalanced charge distribution inside a perovskite-sensitized solar cell

Bergmann, V.; Weber, Stefan A. L.; Ramos, F. Javier; Nazeeruddin, Mohammad Khaja; Grätzel, Michaël; Li, Dan; Domanski, Anna L.; Lieberwirth, Ingo; Ahmad, Shahzada; Berger, Rüdiger

doi:10.1038/ncomms6001

Cited by 317 publications

(340 citation statements)

References 29 publications

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“…There is also debate about how to correctly measure the recombination and transport times, the charge density, and even the correct measurement of efficiency. [5][6][7][8][9][10][11][12][13][14][15][16][17] The debate about characterization centers on the interpretation of various time constants that can be measured by optical and electrical means. These time constants range from <1 µs to >100 µs.…”

Section: Introductionmentioning

confidence: 99%

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO₂: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

et al. 2015

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We have examined methylammonium lead iodide (MAPI) cells of the design FTO/sTiO 2 / mpTiO 2 /MAPI/Spiro-OMeTAD/Au using fast opto-electronic techniques including transient photovoltage, differential capacitance, charge extraction, current interrupt, and chronophotoamperometry. The data allow several important conclusions regarding the physics and proper characterization of these cells. 1) In mpTiO 2 /MAPI cells there are two kinds of extractable charge stored under operation: a capacitive electronic charge (~0.2 µC/cm 2 ), and another, much larger, charge (40 µC/cm 2 ) which could be the result of dipole realignment, or the effect of mobile ions. The capacitive charge is ~10 times smaller than in mpTiO 2 /dye/SpiroOMeTAD cells with similar mpTiO 2 thickness. 2) Transient photovoltage decays are strongly double exponential with two time constants that differ by a factor of ~5, independent of bias light intensity. We show that the fast decay (~1 µs at one sun) can be assigned to the predominant charge recombination pathway in the cell. We examine and reject the possibilities that the fast decay is due to ferro-electric relaxation, or to the bulk photovoltaic effect. We provide two possible schematic electrical models for the cells that reproduce the V oc and TPV data.3) It has been previously observed that MAPI cells frequently show current/voltage hysteresis. For example, an increase in J sc and V oc is observed on the return sweep of a cyclic JV. Our capacitance vs V oc data indicate that the hysteresis involves a change in internal potential gradients, most likely a shift in band offsets at the TiO 2 /MAPI interface. The TPV results show that the V oc hysteresis is not due to a change in recombination rate constant. Calculation of recombination flux at V oc shows that the hysteresis is also not due to an increase in charge separation efficiency, and that charge generation is not a function of applied bias. We also show that the JV hysteresis is not a light driven effect, but is caused by exposure to forward bias, light or dark.

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Section: Introductionmentioning

confidence: 99%

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO₂: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

et al. 2015

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“…KPFM was recently used to characterize the perovskite top layer [39,40] , where the presence of a small potential barrier at the grain boundaries was found. Bergmann et al have recently measured cross-sections of a complete perovskite based solar cell under illumination with KPFM and showed that the potential is similar to a p-i-n type junction [41] . Figure 5 shows CPD of line profiles recorded at pristine and additive based perovskite films which is sensitive to the surface work functions Φ of the materials.…”

Section: Kelvin Probe Force Microscopy (Kpfm)mentioning

confidence: 99%

Impact of Monovalent Cation Halide Additives on the Structural and Optoelectronic Properties of CH₃NH₃PbI₃ Perovskite

Abdi‐Jalebi

Dar

Sadhanala

et al. 2016

Advanced Energy Materials

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We report the influence of monovalent cation halide additives on the optical, excitonic and electrical properties of CH 3 NH 3 PbI 3 perovskite. Monovalent cation halide with similar ionic radii to Pb 2+ , including Cu + , Na + and Ag + , were added to explore possibility of doping. We observed significant reduction of subbandgap optical absorption and lower energetic disorder along with a shift in the Fermi level of the perovskite in the presence of these cations. The bulk hole mobility of the additive based perovskites as estimated using the space charge limited current method exhibited an increase of up to an order of magnitude compared to the pristine perovskites with a significant decrease in the activation energy.Consequentially, enhancement in the photovoltaic parameters of additive-based solar cells was achieved.We observed an increase in open circuit voltage for AgI (~1.02 vs 0.95 V for the pristine) and photocurrent density for NaI and CuBr based solar cells (≈23 vs 21 mA.cm -2 for the pristine). This enhanced photovoltaic performance could be attributed to the formation of uniform and continuous perovskite film, better conversion and loading of perovskite as well as the enhancement in the bulk charge transport along with a minimization of disorder, pointing towards possible surface passivation.

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“…Furthermore, methods such as Kelvin probe force microscopy (KPFM) [148,149] and electron-beam-induced current (EBIC) measurements [150,151] allowed for the measurement of the potential and current distribution within a device, providing more direct evidence for a charge trapping and detrapping process. In these experiments, the charge-carrier-density distribution across the cross-section of the device was measured, allowing one to track the evolution of accumulated charges after illumination.…”

Section: Wwwadvancedsciencenewscommentioning

confidence: 99%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

Advanced Energy Materials

317

201

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following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

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Real-space observation of unbalanced charge distribution inside a perovskite-sensitized solar cell

Cited by 317 publications

References 29 publications

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO₂: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO₂: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

Impact of Monovalent Cation Halide Additives on the Structural and Optoelectronic Properties of CH₃NH₃PbI₃ Perovskite

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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Real-space observation of unbalanced charge distribution inside a perovskite-sensitized solar cell

Cited by 317 publications

References 29 publications

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO2: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO2: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

Impact of Monovalent Cation Halide Additives on the Structural and Optoelectronic Properties of CH3NH3PbI3 Perovskite

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO₂: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO₂: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J–V Hysteresis

Impact of Monovalent Cation Halide Additives on the Structural and Optoelectronic Properties of CH₃NH₃PbI₃ Perovskite