Sudhakar Narra

National Yang Ming Chiao Tung University

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Eric Wei‐Guang Diau

National Yang Ming Chiao Tung University

Efat Jokar

Sungkyunkwan University

Sumit S. Bhosale

Institut National de la Recherche Scientifique

C. C. Tsai

National Yang Ming Chiao Tung University

Nobuhiro Ohta

National Yang Ming Chiao Tung University

Yaw‐Wen Yang

National Synchrotron Radiation Research Center

Kamlesh Awasthi

National Yang Ming Chiao Tung University

Murali Krishna Pola

National Yang Ming Chiao Tung University

Yu‐Pei Lin

National Yang Ming Chiao Tung University

Hui‐Ping Wu

Sun Yat-sen University

Cooperative Institutions

National Yang Ming Chiao Tung University

National Tsing Hua University

National Taiwan University

National Synchrotron Radiation Research Center

National Hsinchu University of Education

National Cheng Kung University

Academia Sinica

Hokkaido University

RIKEN Center for Emergent Matter Science

National Taiwan University of Science and Technology

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Optical Characterizations for Broadening Emissions from Doping of the Two-Dimensional Tin–Lead Perovskite Films

The Journal of Physical Chemistry C (2024)

Sudhakar Narra Wei‐Chuan Chen Ashank Seetharaman I‐Hua Tsai Eric Wei‐Guang Diau

In this work, we present the optical properties of two-dimensional (2D) perovskite films of BA2SnxPb(1–x)I4 with x = 0–1. The excitonic absorption peaks of the fabricated perovskite samples were shown to shift to lower energies with increase of the Sn proportions in the films, whereas their emission spectra were shown to display dramatic Stokes shifts and spectral broadening from 600 to 1100 nm when compared with their pristine analogues. Power-dependent PL studies indicate that the emissions in the fabricated 2D perovskite samples arise from the self-trapping of excitons, while the spectral broadening originates from the production of multiple defect states upon doping of small amounts of Sn in the Pb-rich samples. The bandwidths of the emission spectra of the Pb–Sn mixed 2D perovskite samples were larger when the Pb proportion was higher than the Sn proportion, a key indicator for increasing the bandwidth of the white-light emission. TA spectral studies reveal that the nature of trap states plays a prominent role in the spectral broadening of the emission of the Pb-rich perovskite samples.

Tin dioxide

10.1021/acs.jpcc.3c07717

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Citations (1)

Morphology-Dependent Charge-Separated Character in the Photoexcited States of the Photocatalytic Bismuth Oxyiodide Nanocrystals and Nanosheets: Implications for Photodynamic Therapy

ACS Applied Nano Materials (2025)

Shailesh Rana I‐Hua Tsai Kamlesh Awasthi Sudhakar Narra Sumit S. Bhosale

Bismuth oxyiodide (BiOI), a two-dimensional material, is well known for its photocatalytic and photovoltaic properties owing to its low bandgap, efficient charge separation, and suitable work function that facilitates various photocatalytic reactions. However, the performance of BiOI depends on the synthetic methods, as they dictate the growth directions and overall quality of the nanosheets or crystals produced. Herein, we investigated the morphology and the charge-separated character in the photoexcited states of the BiOI nanocrystals/sheets produced from alternative synthetic routes such as hydrothermal, ball milling, and hand grinding methods by using electroabsorption (E-A) spectroscopy. The optical band gaps, absorption, and E-A spectra of BiOI are shown to be sensitive to the synthetic method. The E-A spectra of BiOI nanocrystals/sheets embedded in poly(methyl methacrylate) (PMMA) matrix measured at the second harmonic of the applied field were simulated by using integral method analysis to estimate the changes in electric dipole moment and polarizability following photoexcitation. From the analysis, it is found that BiOI nanosheets prepared using a hand grinding method with a [001] orientation have much larger charge-separated character in the photoexcited states than those in the nanoparticles prepared from hydrothermal and ball milling methods with a [110] orientation, implying the excellent photoelectronic performance in BiOI nanosheets prepared by the hand grinding method in comparison with BiOI nanoparticles prepared by other methods. The present finding may open the gateway for the development of the specific BiOI material, which is suitable for photocatalysis and photodynamic therapy.

Bismuth

Morphology

10.1021/acsanm.4c06892

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CSD 2081243: Experimental Crystal Structure Determination

The Cambridge Structural Database (2018)

C. C. Tsai Yu‐Pei Lin Murali Krishna Pola Sudhakar Narra Efat Jokar

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Crystal (programming language)

10.25505/fiz.icsd.cc27vpwp

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Self-Photocatalytic Splitting of Carbon Dioxide Using Co-cationic Perovskite Nanocrystals in the Absence of Water

ACS Energy Letters (2022)

Sumit S. Bhosale Aparna K. Kharade Sudhakar Narra Sue-min Chang Eric Wei‐Guang Diau

Environmental concerns demand efficient removal of CO2, a major greenhouse gas. For this purpose, a traditional chemical strategy implements a catalytic conversion of CO2 to CO, with H2O as the sacrificial agent to generate O2. Herein we report the first self-photocatalytic conversion of CO2 to generate CO and O2 in the absence of H2O, using co-cationic perovskite nanocrystal Cs0.55FA0.45PbBr3. We obtained a record production rate 105 μmol g–1 h–1 of CO, which is three times that with CsPbBr3 as photocatalyst at the gas–solid interface. During photocatalytic reaction, a phase transition occurred with an enlarged crystal size through the effect of Ostwald ripening, for which the CO yield approached 3.1 mmol g–1 within the reaction period of ∼60 h. During this process, both FA and oleylammonium cations were released to provide the proton source for the CO2 reduction to proceed and generate hydroxyl species required for oxidation. A self-photocatalysis mechanism involving bound hydroxyls is proposed.

Cationic polymerization

Ostwald ripening

Carbon fibers

10.1021/acsenergylett.2c02342

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Diffusion of bulky organic cations in the 3D/2D heterostructures to form interfacial quasi-2D (N2) phase for tin perovskite solar cells

Journal of Materials Chemistry A (2023)

Ashank Seetharaman Sudhakar Narra Parameswaran Rajamanickam P. Raghunath M. C. Lin

A simple forceps-assisted pressing of two thin films with E1 (3D) and N1 (2D) phases to build multilayered perovskite heterostructures for lead-free perovskite solar cell application.

10.1039/d3ta03539e

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Fe³⁺ Assisted Synthesis of Stable 3D‐in‐2D CsPbBr₃/CsPb₂Br₅ Nanocomposites for Optical Gain Media

Advanced Optical Materials (2024)

Sumit S. Bhosale Sudhakar Narra Ruiqi Yang Aycan Yurtsever François Légaré

Abstract Metal halide perovskite nanocrystals are sought after for many optical and optoelectronic applications, such as light‐emitting diode and solar cells, due to their outstanding optical properties. However, their ionic nature makes them susceptible to ambient conditions. One rational solution to this challenge is the passivation or encapsulation of perovskite nanocrystals to isolate them from their environments. Thus, there is an urgent need to develop efficient methods for encapsulating emissive perovskite nanocrystals. A facile post‐synthesis method is proposed to treat Cs x FA (1−x) PbBr 3 nanocrystals, in the presence of Fe 3+ cations, to create a robust and water‐stable nanocomposite structure, where 3D CsPbBr 3 nanocrystals are embedded in and thus protected by the 2D CsPb 2 Br 5 nanosheets (named as CsPbBr 3 /CsPb 2 Br 5 hereafter). These Fe 3+ cations facilitate the formation of the CsPbBr 3 /CsPb 2 Br 5 composite and regulate the growth of 2D CsPb 2 Br 5 sheets. By performing controlled experiments, the possible mechanism of 2D nanosheet growth is proposed and discussed in detail. More importantly, the composite can remain stable in water for three months and exhibits amplified spontaneous emission under femtosecond laser irradiation. This work presents a synthesis pathway for producing durable perovskite composites that are promising for future lasing applications.

10.1002/adom.202401470

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Interface-Enhanced Charge Recombination in the Heterojunction between Perovskite Nanocrystals and BiOI Nanosheets Serves as an S-Scheme Photocatalyst for CO₂ Reduction

The Journal of Physical Chemistry Letters (2022)

Atul H. Bhosale Sudhakar Narra Sumit S. Bhosale Eric Wei‐Guang Diau

We designed an S-heterojunction system with a perovskite nanocrystal, Cs1–xFAxPbBr3 (CF), coupled with a bismuth oxyiodide (BiOI) nanosheet to form a perovskite heterojunction (PHJ) photocatalyst. On the basis of femtosecond transient absorption measurements, the pristine CF sample has two charge recombination periods, 100 and 900 ps, corresponding to surface and bulk trap-state relaxations, respectively. When CF was in contact with BiOI to form an S-heterojunction, rapid interfacial charge recombination occurred to show two decay components with time coefficients 1 and 35 ps, responsible for the electron–hole recombination in the surface and bulk states, respectively. We observed a new photoinduced absorption band on the blue side of the photobleach band of PHJ that gives relaxation more rapid than that of pristine CF, presumably due to doping of bismuth cations creating defect states to enhance the charge recombination that leads to photocatalytic performance for the PHJ catalyst poorer than for the pristine CF sample.

Interface (matter)

Charge carrier

10.1021/acs.jpclett.2c02153

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Citations (18)

Control of preferred orientation with slow crystallization for carbon-based mesoscopic perovskite solar cells attaining efficiency 15%

Journal of Materials Chemistry A (2016)

C. C. Tsai Guan-Wei Wu Sudhakar Narra Hung-Ming Chang Nayantara Mohanta

Fabrication of mesoporous carbon-based perovskite solar cells via slow crystallization using NMP solvent attained a great device efficiency of 15% with preferred orientation of the crystals at the (004) facet.

Mesoscopic physics

Facet (psychology)

Carbon fibers

10.1039/c6ta09036b

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Citations (84)

Optimization of a compact layer of TiO₂via atomic-layer deposition for high-performance perovskite solar cells

Sustainable Energy & Fuels (2017)

Ahmed Esmail Shalan Sudhakar Narra Tomoya Oshikiri Kosei Ueno Xu Shi

Configuration of the perovskite solar cell and diagram of the mechanism of preparation of TiO₂ using atomic-layer deposition.

Deposition

10.1039/c7se00220c

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Citations (62)

Electroabsorption Studies of Multicolored Lead Halide Perovskite Nanocrystalline Solid Films

ACS Photonics (2018)

Kamlesh Awasthi Kai-Bo Du Chi‐Yung Wang Chao-Lin Tsai Morihiko Hamada

Electroabsorption (E-A) spectra of lead halide perovskites, that is, CH3NH3PbI3–xBrx (x = 0–3), which show large spectral shift depending on the ratio between iodine and bromide, have been measured. By analyzing E-A spectra with the integral method, spectral shape of the absorption spectra for the first exciton band and binding energy of exciton have been determined. Magnitudes of the change in electric dipole moment and molecular polarizability following excitation into the exciton state have been also evaluated in these perovskites. The binding energy of electron and hole in exciton of these materials as well as the magnitude of change in electric dipole moment following exciton absorption is roughly the same, suggesting that the difference of the photoenergy conversion in photovoltaic cells using these materials comes from the difference in light harvesting effect and difference in carrier mobility, not from the difference in carrier generation efficiency. The frequency-dependent third-order nonlinear susceptibility χ(3) has also been calculated, based on the E-A spectra.

Nanocrystalline material

10.1021/acsphotonics.8b00185

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Citations (19)