Thermochromic Cs<sub>2</sub>AgBiBr<sub>6</sub> Single Crystal with Decreased Band Gap through Order‐Disorder Transition

Zhang, Yaru; Song, Yilong; Lu, Yuan; Zhang, Zhuang; Wang, Yan; Yang, Yang; Dong, Qingfeng; Yu, Yi; Qin, Peng; Huang, Fuqiang

doi:10.1002/smll.202201943

Cited by 21 publications

(21 citation statements)

References 41 publications

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“…Together with these three modes, we observed a broad peak (multiphoton peaks) at 355 cm –1 , which corresponds to the second order of the A 1g mode at 185.1 cm –1 , respectively . As a result of the substantial difference in electronegativity between Ag–Br (1.03) and Bi–Br (0.94), it was suggested in the literature that the bonding strength of Ag–Br type bonds is significantly higher than that of Bi–Br bonds, allowing it to be treated as a discrete-like entity (0D electronic dimensionality). − …”

mentioning

confidence: 70%

Elucidating Polaron Dynamics in Cs₂AgBiBr₆ Double Perovskite

Tailor

Saini

Yadav

et al. 2023

J. Phys. Chem. Lett.

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Lead-free Cs2AgBiBr6 double perovskites have recently emerged as a possible alternative to lead-based halide perovskites for photovoltaic and optoelectronic applications. Significant research efforts have been devoted toward device engineering to enhance the performance of Cs2AgBiBr6 double-perovskite-based photovoltaic and optoelectronic devices; however, less attention has been paid to address their intrinsic photophysical properties. In this work, we have shown that the small polaron formation under photoexcitation and polaron localization limits the carrier dynamics in Cs2AgBiBr6 double halide perovskites. Furthermore, temperature-dependent ac conductivity measurement reveals that single polaron hopping is the dominant conduction mechanism. Ultrafast transient absorption spectroscopy reveals that a deformed lattice under photoexcitation leads to the formation of small polarons which act as self-trapped states (STSs) and lead to the ultrafast trapping of charge carriers. Our findings provide an in-depth understanding of intrinsic limitations of Cs2AgBiBr6 perovskites, which can be applicable for other bismuth-based semiconductors.

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mentioning

confidence: 70%

Elucidating Polaron Dynamics in Cs₂AgBiBr₆ Double Perovskite

Tailor

Saini

Yadav

et al. 2023

J. Phys. Chem. Lett.

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“…[ 39 ] Later, Huang and co‐workers observed that simply postannealing a Cs 2 AgBiBr 6 crystal at 400 °C for 24 h could decrease the bandgap to around 1.69 eV (Figure 11i). [ 40 ] These results imply the thermal energy may be the driving force to overcome the order‐to‐disorder transition barrier to achieve partially disordered Cs 2 AgBiBr 6 crystals. It is noted that a direct evidence of atomic rearrangement is still missing.…”

Section: Challenges and Efforts In Hdps Solar Cellsmentioning

confidence: 99%

Challenges and Progress in Lead‐Free Halide Double Perovskite Solar Cells

Boschloo

Wang

et al. 2023

Solar RRL

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Lead-based metal halide perovskites have brought a revolution in photovoltaics in the last few years with a dramatic increase in the power conversion efficiency (PCE) from 3.8% in 2009 to 25.7% in 2022. [1,2] The incredible PCE improvement is mainly due to their remarkable optical and electrical properties, including suitable and tunable direct bandgap, high absorption coefficient, small exciton binding energy, long carrier diffusion length and lifetime, high carrier mobility, high defect tolerance, etc. [3][4][5][6][7] Besides, low-cost and printable devices have further prospered this fantastic technology. [8] Despite these exciting achievements, Pb-based perovskites suffer from two significant issues: toxicity and long-term instability. [9,10] The toxicity issue comes from the Pb which can induce detrimental environmental and health effects in the case of leakage. For long-term instability, Pd-based perovskites are susceptible to degradation after exposure to light, oxygen, moisture, or heat, ascribed to polymorphic transformation, hydration, or decomposition. Both of these issues hinder their further development and commercialization.A straightforward way to address the instability and Pb toxicity issues is to develop stable and lead-free perovskites. The first substitution candidate is Sn 2þ , as it is in the same group of the periodic table as Pb with similar lone pairs. As expected, these Sn 2þ -based materials maintain the 3D perovskite structure and exhibit relatively high PCE. [11] A critical issue for Sn-based perovskites is the easy oxidization of Sn 2þ to Sn 4þ . Moreover, Sn 2þ might be also harmful to the human body due to the strong acidification induced by the SnI 2 . [9] Instead of Sn 2þ , more stable elements such as Ag þ , Na þ , Bi 3þ , Sb 3þ , In 3þ , Fe 3þ , Ti 4þ , Pd 4þ , etc. were employed to form various novel lead-free perovskites or perovskite derivatives, including A 3 B 3þ 2 X 9 , [12] A 2 B 4þ X 6 , [13] B þ B 3þ 2 X 7 , [14] A 2 B þ B 2þ X 5 , [15] and halide double perovskites (HDPs) A 2 B þ B 3þ X 6 [16] (A = Cs þ , MA þ , FA þ ; B = metal ions; X = Cl À , Br À , I À ). Unfortunately, except for HDPs (A 2 B þ B 3þ X 6 ), the crystal dimensionalities of other materials are 2D or 0D, different from the 3D structure of connected BX 6 octahedra in Pb-based perovskites. Generally, the drawbacks of the low structural dimensionality (0D-2D) are poor carrier transport, high carrier effective masses, and exciton binding energies, limiting their applications in photovoltaics. Therefore, lead-free perovskite candidates with high structure dimensionality are more favorable for high-efficiency photovoltaics.Recently, HDPs (A 2 B þ B 3þ X 6 ) with 3D perovskite structure and exciting optoelectronic properties are becoming one of the most promising Pb-free perovskite candidates in photovoltaic applications. The benchmark HDP Cs 2 AgBiBr 6 for solar cells was first reported in 2017. [17] Afterward, this material has been explored for various photoelectric applications, including photodetectors...

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“…Recent reports indicate that this may be possible using single‐Cs 2 AgBiBr 6 crystals or polycrystalline Cs 2 AgBiBr 6 with significantly lower defects. [ 5,7,31 ] Using the realistic case of asymmetric diffusion lengths typically reported for polycrystalline Cs 2 AgBiBr 6 thin films, the bifacial architecture may exhibit a significantly improved PCE compared to the standard architecture. This result confirms that the asymmetric carrier diffusion length of Cs 2 AgBiBr 6 is highly detrimental to its PV efficiency.…”

Section: Bifacial Architecturementioning

confidence: 99%

“…[ 3 ] In contrast to lead (Pb)‐based perovskite materials, Cs 2 AgBiBr 6 denotes another family of perovskite structures that are relatively stable and contain no toxic elements. [ 4 ] These beneficial characteristics, in conjunction with low‐cost solution processing, mean that Cs 2 AgBiBr 6 has the potential not only for PV applications, but also in other fields such as X‐ray detectors, [ 5 ] photocatalysts, [ 6 ] smart windows, [ 7 ] and optical switching memory. [ 8 ]…”

Section: Introductionmentioning

confidence: 99%

Overcoming the Performance Limitation of Cs₂AgBiBr₆ Double Perovskites Using Bifacial Photovoltaic Design

Muzammil

Adhyaksa

2022

Energy Tech

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Cs2AgBiBr6 is an encouraging example of perovskites which shows potential toward the development of more stable and nontoxic photoactive materials. However, relative to its necessarily large optical thickness, the material has substantially deficient electron diffusion lengths, which limit its photovoltaic efficiency. Herein, this problem is solved by designing a double‐sided semitransparent architecture for a Cs2AgBiBr6‐based photovoltaic material. In this case, the bifacial design deliberately creates an imbalance between the electron and hole densities, resulting in asymmetric lengths of carrier conduction near their respective transporting layers. Coupled optoelectronic simulations suggest that the use of the bifacial architecture results in an improvement of around 34% in the efficiency, from 3.47% to 4.64%, compared to the standard configuration. This method is effective to improve electron conduction in Cs2AgBiBr6, which is typically severe compared to its hole conduction. Finally, the strength of the correlation between the power conversion efficiency of the bifacial architecture and the diffusion length, asymmetric ratio of electron and hole conduction, and light albedo factor are explored. The results highlight some ways to improve the photovoltaic efficiency of Cs2AgBiBr6 above 8%, for instance, through tuning the surface recombination and band alignment between Cs2AgBiBr6 and the hole‐transporting layer.

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Thermochromic Cs₂AgBiBr₆ Single Crystal with Decreased Band Gap through Order‐Disorder Transition

Cited by 21 publications

References 41 publications

Elucidating Polaron Dynamics in Cs₂AgBiBr₆ Double Perovskite

Elucidating Polaron Dynamics in Cs₂AgBiBr₆ Double Perovskite

Challenges and Progress in Lead‐Free Halide Double Perovskite Solar Cells

Overcoming the Performance Limitation of Cs₂AgBiBr₆ Double Perovskites Using Bifacial Photovoltaic Design

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Thermochromic Cs2AgBiBr6 Single Crystal with Decreased Band Gap through Order‐Disorder Transition

Cited by 21 publications

References 41 publications

Elucidating Polaron Dynamics in Cs2AgBiBr6 Double Perovskite

Elucidating Polaron Dynamics in Cs2AgBiBr6 Double Perovskite

Challenges and Progress in Lead‐Free Halide Double Perovskite Solar Cells

Overcoming the Performance Limitation of Cs2AgBiBr6 Double Perovskites Using Bifacial Photovoltaic Design

Contact Info

Product

Resources

About

Thermochromic Cs₂AgBiBr₆ Single Crystal with Decreased Band Gap through Order‐Disorder Transition

Elucidating Polaron Dynamics in Cs₂AgBiBr₆ Double Perovskite

Elucidating Polaron Dynamics in Cs₂AgBiBr₆ Double Perovskite

Overcoming the Performance Limitation of Cs₂AgBiBr₆ Double Perovskites Using Bifacial Photovoltaic Design