Performance and Stability of Lead Perovskite/TiO<sub>2</sub>, Polymer/PCBM, and Dye Sensitized Solar Cells at Light Intensities up to 70 Suns

Law, Chun Hung Roberts; Miseikis, Lukas; Dimitrov, Stoichko D.; Shakya-Tuladhar, Pabitra; Li, Xiaoe; Barnes, Piers R. F.; Durrant, James R.; O’Regan, Brian C.

doi:10.1002/adma.201402612

Cited by 105 publications

(90 citation statements)

References 21 publications

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“…The PCDTBT devices in addition have their J SC -V OC curves more limited at high voltages compared to the other cells, despite the higher bandgap energy of the PCDTBT material being in principle less limiting. While the V OC of this cell is indeed higher, it appears, as also recently noted, [ 34 ] more limited by surface recombination at the electrodes. We expect the limiting electrode to be the PEDOT:PSS hole selective material, but further studies are needed to clarify this issue.…”

Section: Temperature Dependencementioning

confidence: 70%

Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency

Tvingstedt

Deibel

2016

Advanced Energy Materials

113

135

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provides information on which types of recombination are ruling the loss of voltage at a specifi c illumination intensity. Several efforts in literature aim at determining the ideality factor by steady state techniques with the objective to also understand the dominant recombination mechanism. Currently there is, however, a substantial disagreement of the reported values of the ideality factor for several identical materials studied [ 3 ] and literature related to organic photovoltaic cells (OPV) ideality factors currently provides values ranging from 0.6 [ 4 ] via unity [ 5 ] up to values as high as 20. [ 6 ] This large range is surely doubtful to be correct. The Shockley diode equation is of fundamental importance for solar cells as it solely describes the general voltage and temperature dependent recombination processes.The ideal diode equationwhere q is the electronic charge and k the Boltzmann constant, is therefore actually ruled only by just one material dependent factor, that is the prefactor to the exponential Boltzmann term, frequently referred to as the dark saturation current J 0 . For the ideal diode, J 0 therefore must entail all information related to charge carrier recombination in the photovoltaic material used. The term "dark saturation current" originates from earlier belief of experimentally assigning its value by simply reverse biasing the diode, and measuring the saturated low current value. However, the prefactor J 0 has in fact a much deeper physical meaning, which also bears very little relation to just reverse biasing of a diode. A much better term for J 0 would in the ideal diode case instead be "thermal equilibrium recombination current" as pointed out recently by Cuevas. [ 7 ] Its value is then exclusively determined by the material properties (i.e., bandgap) and the temperature of the material. Hence, in the ideal description of Equation ( 1) the value of the equilibrium recombination current J 0 is therefore always independent of external factors such as illumination or applied voltage, but on the other hand strongly dependent on temperature. However, if it is the case that J 0 in itself actually also depends on said external conditions, the term "thermal equilibrium recombination current" becomes less useful, as it is no longer a real constant. As the signifi cance of J 0 partly lied in it being a constant, Complementary electroluminescence measurements attest that the current density dependence of the ability of the solar cell to emit light is better correlated to the series resistance free ideality factor. For the studied set of OPV devices it is observed that the ideality factors are quite low, and with very weak temperature dependence. The J SC -V OC method to determine ideality factors further allows good estimates of activation energies as well as recombination current prefactors J 00 . The fi ndings imply that the principal OPV non-radiative recombination mechanism is not recombination of free carriers with trapped carriers in an exponential density of tail states as previou...

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Section: Temperature Dependencementioning

confidence: 70%

Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency

Tvingstedt

Deibel

2016

Advanced Energy Materials

113

135

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“…In spite of the increased understanding and improvements made regarding the moisture stability, encapsulation of the devices is still key for long-term stability. [241] …”

Section: Moisturementioning

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

312

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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“…10 Thus efforts to prevent moisture ingress 11 or careful device encapsulation are required to achieve significant stability under operation. 12 This paper concerns the interaction of MAPI with water. The formation of colorless mono-hydrated methyl ammonium lead iodide (CH 3 NH 3 PbI 3 •H 2 O) from MAPI crystals in aqueous solution at temperatures below 40 °C was described in 1987 by Poglitsch and Webber.…”

Section: Introductionmentioning

confidence: 99%

Reversible Hydration of CH₃NH₃PbI₃ in Films, Single Crystals, and Solar Cells

et al. 2015

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Solar cells comprising methylammonium lead iodide perovskite (MAPI) are notorious for their sensitivity to moisture. We show that hydrated crystal phases are formed when MAPI is exposed to water vapour at room temperature and that these phase changes are fully reversed when the material is subsequently dried. The reversible formation of CH 3 NH 3 PbI 3 •H 2 O followed by (CH 3 NH 3 ) 4 PbI 6 •2H 2 O (upon long exposure times) was observed using time resolved XRD and ellipsometry of thin films prepared using 'solvent engineering', single crystals, and state of the art solar cells. In contrast to water vapour, the presence of liquid water results in the irreversible decomposition of MAPI to form PbI 2 . MAPI changes from dark brown to transparent on hydration; the precise optical constants of CH 3 NH 3 PbI 3 •H 2 O formed on single crystals were determined, with a bandgap at 3.1 eV. Using the single crystal optical constants and thin film ellipsometry measurements, the time dependent changes to MAPI films exposed to moisture were modelled. The results suggest that the mono-hydrate phase forms independently of the depth in the film suggesting rapid transport of water molecules along grain boundaries. Vapour phase hydration of an unencapsulated solar cell (initially J sc ≈ 19 mA cm -2 and V oc ≈ 1.05 V at 1 sun) resulted in more than a 90 % drop in short circuit photocurrent and around 200 mV loss in open circuit potential, but these losses were fully reversed after the cell was exposed to dry nitrogen for 6 hours. Hysteresis in the current-voltage characteristics was significantly increased after this dehydration, which may be related to changes in the defect density and morphology of MAPI following recrystallization from the hydrate. Based on our observations we suggest that irreversible decomposition of MAPI in the presence of water vapour only occurs significantly once a grain has been fully converted to the hydrate phase.

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Performance and Stability of Lead Perovskite/TiO₂, Polymer/PCBM, and Dye Sensitized Solar Cells at Light Intensities up to 70 Suns

Cited by 105 publications

References 21 publications

Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency

Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency

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

Reversible Hydration of CH₃NH₃PbI₃ in Films, Single Crystals, and Solar Cells

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Performance and Stability of Lead Perovskite/TiO2, Polymer/PCBM, and Dye Sensitized Solar Cells at Light Intensities up to 70 Suns

Cited by 105 publications

References 21 publications

Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency

Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency

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

Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells

Contact Info

Product

Resources

About

Performance and Stability of Lead Perovskite/TiO₂, Polymer/PCBM, and Dye Sensitized Solar Cells at Light Intensities up to 70 Suns

Reversible Hydration of CH₃NH₃PbI₃ in Films, Single Crystals, and Solar Cells