Enhancement in efficiency and optoelectronic quality of perovskite thin films annealed in MACl vapor

Khadka, Dhruba B.; Shirai, Yasuhiro; Yanagida, Masatoshi; Masuda, Toshio; Miyano, Kenjiro

doi:10.1039/c7se00033b

Cited by 80 publications

(98 citation statements)

References 81 publications

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“…as a mixture with PbI 2 in DMF (and then MAI converted the film to MAPbI 3 perovskite). [50,51] To form this mixture, PbI 2 powder first reacted with HI, forming light yellow needle-like 1D HPbI 3 non-perovskite compound.…”

Section: Two-step Conversionmentioning

confidence: 99%

Μethylammonium Chloride: A Key Additive for Highly Efficient, Stable, and Up‐Scalable Perovskite Solar Cells

Kosmatos

Theofylaktos

Giannakaki

et al. 2019

Energy & Environ Materials

100

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Lead halide perovskites of the type APbX3 (where A = methylammonium MA, formamidinium FA, or cesium and X = iodide and bromide), in a single‐crystal form or more often as polycrystalline films, have already shown unique optoelectronic properties, comparable with those of the best single‐crystal semiconductors. To form a properly crystalline iodide or iodide/bromide, perovskite and achieve high performance in solar cells, sources containing only iodide and bromide salts (PbI2, PbBr2, MAI, FAI, CsI, MABr) are typically used as precursor materials. However, recently, most of the record perovskites contain MACl as additive to control their crystallization, revisiting the importance of methylammonium cation excess and chloride incorporation in perovskites, previously highlighted by Snaith's group back in 2012. Here, we review the background and recent progress in MACl‐mediated crystallization of perovskites, as well as the impact of the additive in solar cells. In particular, we describe the current understanding of the mechanism of perovskite crystallization process and defect passivation at grain boundaries in the presence of MACl. We then discuss the spectacular results (in terms of record efficiencies, stability, and up‐scaling) that have been delivered by solar cells employing MACl‐incorporated perovskites, and give an outlook of future research avenues that might bring perovskite solar cells closer to commercialization.

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Section: Two-step Conversionmentioning

confidence: 99%

Μethylammonium Chloride: A Key Additive for Highly Efficient, Stable, and Up‐Scalable Perovskite Solar Cells

Kosmatos

Theofylaktos

Giannakaki

et al. 2019

Energy & Environ Materials

100

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“…We find the time constant of the hole injection and the quantity of the injected holes depend crucially on the choice of the HTM, and discuss the observed hole injection dynamics in comparison with the device performance of the solar cells containing the same interfaces. Samples for spectroscopic measurements consist of a glass substrate, a thin layer of HTM prepared by either spin-coating (PTAA and PEDOT:PSS) or sputtering (NiO x ) [15,16], and a 250-nm thick crystalline MAPbI 3 film [17,18], as schematically shown in Fig. 1b.…”

mentioning

confidence: 99%

Direct Observation of Ultrafast Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy

Ishioka

Barker

Yanagida

et al. 2017

J. Phys. Chem. Lett.

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Efficient charge separation at the interfaces between the perovskite and with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion efficiency. We systematically investigate the hole injection dynamics from MAPbI3 perovskite to three typical hole transport materials (HTMs) PEDOT:PSS, PTAA and NiOx by means of pump-probe transmission measurements. We photoexcite only near the MAPbI3/HTM interface or near the back surface, and measure the differential transient transmission between the two excitation configurations to extract the carrier dynamics directly related to the hole injection. The differential transmission signals directly monitor the hole injections to PTAA and PEDOT:PSS being complete within 1 and 2 ps, respectively, and that to NiOx exhibiting an additional slow process of 40 ps time scale. The obtained injection dynamics are discussed in comparison with the device performance of the solar cells containing the same MAPbI3/HTM interfaces.Lead halide perovskite photovoltatic cells have been developing rapidly in the past few years, with their power conversion efficiency (PCE) now exceeding 22% [1]. The perovskites are direct semiconductors, and their photovoltatics can in principle work as a model p-i-n diode [2]. The difficulty in the controlled impurity doping in the perovskites can be circumvented by sandwiching the perovskite film between thin layers of electron-and holetransporting materials (ETM and HTM) in the planar heterojunction structure [3]. These carrier transporting layers enable efficient and irreversible separation of the electrons and holes photoexcited in the perovskite, and thereby lead to the high PCE of the perovskite solar cells. Whereas various inorganic and organic materials have been explored as ETM and HTM based on their conduction band minimum (CBM) and valence band maximum (VBM) energies with respect to those of the perovskite, the actual device performance depends very weakly on the energy level offset [3,4] but can be significantly affected by other factors such as perovskite crystalline quality and interfacial defects [5,6].The charge separation dynamics can in principle be monitored directly by means of transient absorption (or transmission) measurements in the visible to teraherz ranges. The time scale of the charge injection from the perovskite to the HTM layer remain controversial despite the extensive previous studies [5][6][7][8][9][10][11][12][13][14], however. The time constant of the hole injection from CH3NH3PbI 3 (MAPbI 3 ) to spiro-OMeTAD in the previous reports, for example, scattered widely from <80 fs [7] to 0.7 ps [8,9] to 8 ps [10]. The hole injection to NiO x was reported to be complete on sub-picosecond time scale [11], whereas those * ishioka.kunie@nims.go.jp to poly(triarylamine) (PTAA), poly(3-hexylthiophee-2,5-diyl (P3HT), and poly [2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b'] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole) (PCPDTBT) were reported to occur on sub-nanosecond time scales [12]. The ...

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“…The IPCE of perovskite solar cells in the shorter wavelength regime <500 nm is strongly influenced by the interface layer and interface quality of devices, whereas the longer wavelength regime, >500 nm, is strongly dependent on the quality of perovskite material and interfaces. [27] This clearly indicates that the interface layer and the interface quality of the THF-guided perovskite devices improved, resulting in reduced recombination and enhanced charge transport property. According to the previous report, [19] the remnant PbI 2 (in the sequential deposition of perovskite) mostly resides at the interface of perovskite and mesoporous TiO 2 layer.…”

Section: Resultsmentioning

confidence: 93%

“…Even though the IPCE was improved in the entire range, the improvement was much higher in the shorter wavelength regime compared with longer wavelength regime (Figure c). The IPCE of perovskite solar cells in the shorter wavelength regime <500 nm is strongly influenced by the interface layer and interface quality of devices, whereas the longer wavelength regime, >500 nm, is strongly dependent on the quality of perovskite material and interfaces . This clearly indicates that the interface layer and the interface quality of the THF‐guided perovskite devices improved, resulting in reduced recombination and enhanced charge transport property.…”

Section: Resultsmentioning

confidence: 99%

Tetrahydrofuran as an Oxygen Donor Additive to Enhance Stability and Reproducibility of Perovskite Solar Cells Fabricated in High Relative Humidity (50%) Atmosphere

et al. 2019

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In sequential deposition method of lead‐halide perovskite material, the PbI2 layer morphology and remnant PbI2 play an important role in enhancing the power conversion efficiency (PCE) of the perovskite solar cell. However, humidity levels affect the PbI2 and perovskite film morphology, resulting in defect sites and recombination centers on the surface and within the bulk of the material, thus impeding the overall device performance and stability. To address this, incorporation of tetrahydrofuran (THF) additive in PbI2–dimethylformamide (DMF) precursor solution is reported, to improve the quality of PbI2 thin films and to prevent the water interaction directly with PbI2 under high humidity environments. The O‐donor THF interacts with PbI2, resulting in a homogeneous, dense, and pinhole‐free layer as compared with the PbI2 layer without additive. The perovskite layer so obtained from the pinhole‐free PbI2 layer is compact, resulting in a significant reduction of defects/traps. The device is fabricated with modified perovskite in ≈50% humidity atmosphere, resulting in 15% efficiency with high reproducibility. Moreover, the THF‐modified non‐encapsulated perovskite device retains 80% PCE after exposure to 50% relative humidity for 20 days. A strategy to fabricate perovskite solar cells, with reproducible efficiency in high humidity atmosphere viable for large‐scale production, is demonstrated.

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Enhancement in efficiency and optoelectronic quality of perovskite thin films annealed in MACl vapor

Abstract: We analyzed and compared quantitatively the optoelectronic characteristics of perovskite PV devices with and without annealing the perovskite layer in a methyl ammonium chloride vapor atmosphere (MACl treatment).

Cited by 80 publications

References 81 publications

Μethylammonium Chloride: A Key Additive for Highly Efficient, Stable, and Up‐Scalable Perovskite Solar Cells

Μethylammonium Chloride: A Key Additive for Highly Efficient, Stable, and Up‐Scalable Perovskite Solar Cells

Direct Observation of Ultrafast Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy

Tetrahydrofuran as an Oxygen Donor Additive to Enhance Stability and Reproducibility of Perovskite Solar Cells Fabricated in High Relative Humidity (50%) Atmosphere

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