Probing longitudinal carrier transport in perovskite thin films <i>via</i> modified transient reflection spectroscopy

Zhao, Shengli; Leng, Jing; Wang, Shiping; Yan, Xianchang; Yin, Z. G.; Yin, Yanfeng; Zhang, Jun; Jin, Shengye

doi:10.1039/d2sc01826h

Cited by 4 publications

(7 citation statements)

References 47 publications

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“…The absorption spectra were fitted by the Elliott's model (Figure S2, Supporting Information) to separate contributions from exciton absorption and continuum absorption. [ 36 ] The exciton binding energies ( E B ) and bandgaps ( E g ) are extracted and determined to be E B = 19.0 meV and E g = 2.25 eV for MAPbBr 3 , and E B = 25.7 meV and E g = 2.21 eV for MAPbBr 3− x I x . The bandgap of MAPbBr 3− x I x is slightly smaller than that of MAPbBr 3 , and the enhanced light absorption platform of MAPbBr 3− x I x between 600 and 800 nm may be ascribed to the surface‐adsorbed iodine on the catalyst.…”

Section: Resultsmentioning

confidence: 99%

Integrating Mixed Halide Perovskite Photocatalytic HI Splitting and Electrocatalysis into a Loop for Efficient and Robust Pure Water Splitting

et al. 2023

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Developing a hydrogen economy to replace traditional fossil fuels is essential for sustainable human development. As two promising H2 production strategies, photocatalytic and electrocatalytic water splitting with large reaction energy barriers still face the great challenges of poor solar‐to‐hydrogen efficiency and large electrochemical overpotentials, respectively. Herein, a new strategy is proposed to disassemble the difficult pure water splitting into two parts that are easy to implement, namely mixed halide perovskite photocatalytic HI splitting for H2 production, and simultaneous electrocatalytic I3− reduction and O2 production. The efficient charge separation, abundant H2 production active sites, and a small HI splitting energy barrier contribute to the superior photocatalytic H2 production activity of MoSe2/MAPbBr3−xIx (CH3NH3+ = MA). Subsequent electrocatalytic I3− reduction and O2 production reactions only need a small voltage of 0.92 V to drive, which is far lower than that of the electrocatalytic pure water splitting (>1.23 V). The molar ratio of H2 (6.99 mmol g−1) to O2 (3.09 mmol g−1) produced during the first photocatalytic and electrocatalytic cycle is close to 2:1, and the continuous circulation of I3−/I− between the photocatalytic and electrocatalytic systems can achieve efficient and robust pure water splitting.

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Section: Resultsmentioning

confidence: 99%

Integrating Mixed Halide Perovskite Photocatalytic HI Splitting and Electrocatalysis into a Loop for Efficient and Robust Pure Water Splitting

et al. 2023

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“…While the interpretation of film TA responses is more complex than that of solutions, the fact that the response is affected by the change in the refractive index opens new opportunities. One of them is the possibility to monitor the change in carrier distribution across the sample. − In traditional TA measurements, the photoinduced change of the sample absorbance depends on the total number of the excited states or the photocarriers but does not depend on carrier distribution in the sample . On the contrary, in films, reflection from the sample surface depends on the refractive index change at the surface (or the surface carrier density) rather than the total number of carriers in the sample.…”

Section: Effect Of Carrier Distribution and Diffusionmentioning

confidence: 99%

Transient Absorption Spectroscopy of Films: Impact of Refractive Index

Pasanen,

Khan,

Odutola

et al. 2024

J. Phys. Chem. C

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Transient absorption spectroscopy is a powerful technique to study the photoinduced phenomena in a wide range of states from solutions to solid film samples. It was designed and developed based on photoinduced absorption changes or that photoexcitation triggers a chain of reactions with intermediate states or reaction steps with presumably different absorption spectra. However, according to general electromagnetic theory, any change in the absorption properties of a medium is accompanied by a change in the refractive properties. Although this photoinduced change in refractive index has a negligible effect on solution measurements, it may significantly affect the measured response of thin films. In this Perspective paper, we examine why and how the measured responses of films differ from their expected "pure" absorption responses. The effect of photoinduced refractive index change can be concluded and studied by comparing the transmitted and reflected probe light responses. Another discussed aspect is the effect of light interference on thin films. Finally, new opportunities of monitoring the photocarrier migration in films and studying nontransparent samples using the reflected probe light response are discussed. Most of the examples provided in this article focus on studies involving perovskite, TiO 2 , and graphene-based films, but the general discussion and conclusions can be applicable to a wide range of semiconductor and thin metallic films.

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“…TR spectroscopy technique, enabling the direct observation and quantification of longitudinal carrier transport within polycrystalline MAPbI 3 films. 35 By the back-exc. TR method, the dynamics of carrier transport along the thickness direction are addressed by spatially separating the pump (excitation) and probe beams on opposite sides of the film (Figure 3c), thereby directly capturing the longitudinal charge transfer from the excitation side to the probe side (Figure 3d).…”

Section: Carrier Diffusion and Surface Recombinationmentioning

confidence: 99%

“…On this basis, Zhao et al have reported the development of a modified back-excitation (back-exc.) TR spectroscopy technique, enabling the direct observation and quantification of longitudinal carrier transport within polycrystalline MAPbI 3 films . By the back-exc.…”

Section: Time-resolved Spectroscopy For Carrier Transport Studymentioning

confidence: 99%

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Carrier Transport in Lead Halide Perovskites

Sun,

Zhang,

Zhao

et al. 2023

J. Phys. Chem. C

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Lead halide perovskites have emerged as one of the most promising candidates for photovoltaic and photonic devices in decades. Motivated by the aim to further improve their optical or optoelectronic performance, revealing the carrier kinetics (e.g., carrier diffusion, directional transport and charge separation) within becomes an essential subject to explore. For the carriers in perovskite semiconductors, time-resolved spectroscopy serves as a sharp “eye” for researchers to observe their underlying behaviors. In this Review, we focus on the recent progress in probing and regulating the carrier transport kinetics in perovskite single crystals, polycrystalline thin films, and two-dimensional perovskites, investigated mainly by time-resolved photoluminescence (TR-PL) and ultrafast transient absorption (TA) spectroscopy. Meanwhile, challenges and outlooks in exploring perovskite carrier transport are discussed. With a deeper understanding of carrier dynamics, we are on the way to uncover the photophysical fundamentals for further improvement in optoelectronic performance of perovskite-based devices.

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Probing longitudinal carrier transport in perovskite thin films via modified transient reflection spectroscopy

Abstract: An accurate characterization on the longitudinal (along the thickness direction) carrier transport property is of significant importance for evaluating the quality and performance of perovskite thin films. Herein, we report...

Cited by 4 publications

References 47 publications

Integrating Mixed Halide Perovskite Photocatalytic HI Splitting and Electrocatalysis into a Loop for Efficient and Robust Pure Water Splitting

Integrating Mixed Halide Perovskite Photocatalytic HI Splitting and Electrocatalysis into a Loop for Efficient and Robust Pure Water Splitting

Transient Absorption Spectroscopy of Films: Impact of Refractive Index

Carrier Transport in Lead Halide Perovskites

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