Single Particle Spectroscopy and Ultrafast Dynamics in CuInS2 QD

Prasun Mandal^a

^aIISER Kolkata, Mohanpur, West Bengal, Kolkata, India

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2025 Conference (MATSUSSpring25)

I-III-VI Colloidal Nanocrystals and Derivatives: From Synthesis to Applications - #ChalcoQD

Sevilla, Spain, 2025 March 3rd - 7th

Organizer: Lukasz Klopotowski

Invited Speaker, Prasun Mandal, presentation 373
DOI: https://doi.org/10.29363/nanoge.matsusspring.2025.373
Publication date: 16th December 2024

CuInS₂ quantum dot (QD) has been considered as one of the choicest toxic-metal-free QDs.^[1-3] CuInS₂ QD exhibit large Stokes shift (145 nm /4265 cm^-1 /530 meV) in the solution phase and the FWHM of its PL emission is quite significant (105 nm /2415 cm^-1 /300 meV). Photoluminescence quantum yield (PLQY) of core-only CuInS₂ QD is quite low (~15%). Although a few ultrafast exciton-dynamical (femtosecond-early nanosecond) investigations have been reported in this QD system,^[4-6] however, there is no report of detailed exciton dynamical analyses to understand (a) low PLQY, (b) large magnitude of Stokes shift and (c) large magnitude of FWHM of PL emission. Moreover, although the excited state lifetime of this QD is quite long (~4 microsecond), however, there is no detailed investigation of exciton dynamics from nanosecond to microsecond time domain. Temperature (4K to 300K) dependent steady-state PL measurement exhibits an emissive state just below the band edge. All these detailed steady-state and dynamical investigations and analyses clearly reveal the reasons behind (a) low PLQY, (b) large magnitudes Stokes shift, and (c) large FWHM of PL emission.

Upon alloy-shelling of this core CuInS₂QD, the PLQY of the core/alloy-shell (CAS) CuInS₂QD increases enormously and a near unity PLQY (0.96) could be achieved.^[7] More interestingly, such high PLQY of CAS CuInS₂QD remains nearly stable for at least one year.^[7] Ultrasensitive single particle spectroscopic investigation with such highly luminescent and stable QD reveal highly suppressed blinking (>80% ON fraction).^[7] Interestingly, exciton trapping and detrapping rates and their ratios have been observed to be dependent on excitation energy/wavelength.^[8] To the best of our knowledge, so far this is the only QD system in which very significant amplitude variations of both hole trapping and detrapping have been observed.^[8] Unlike electron trapping, hole trapping in this CAS CuInS₂QD has been shown to be beneficial.^[8] Simultaneous electron and hole trapping have been shown to be leading to very long ON time (130 s) without blinking, which is so far the highest for a toxic-metal-free QD.^[8]

All these detailed dynamical analyses and the results will be elaborated.

References:

[1] Reiss, P.; Carrière, M.; Lincheneau, C.; Vaure, L.; Tamang, S. Synthesis of Semiconductor Nanocrystals, Focusing on Nontoxic and Earth-Abundant Materials. Chem. Rev. 2016, 116, 10731−10819.

[2] Chen, B.; Pradhan, N.; Zhong, H. From Large-Scale Synthesis to Lighting Device Applications of Ternary I–III–VI Semiconductor Nanocrystals: Inspiring Greener Material Emitters. J. Phys. Chem. Lett. 2018, 9, 435−445.

[3] Yang, L.; Zhang, S.; Xu, B.; Jiang, J.; Cai, B.; Lv, X.; Zou, Y.; Fan, Z.; Yang, H.; Zeng, H. I–III–VI Quantum Dots and Derivatives: Design, Synthesis, and Properties for Light-Emitting Diodes. Nano Lett. 2023, 23, 2443−2453.

[4] Debnath, T.; Maiti, S.; Maity, P.; Ghosh, H. N. Subpicosecond Exciton Dynamics and Biexcitonic Feature in Colloidal CuInS2 Nanocrystals: Role of In–Cu Antisite Defects. J. Phys. Chem. Lett. 2015, 6, 3458−3465.

[5] Berends, A. C.; Rabouw, F. T.; Spoor, F. C. M.; Bladt, E.; Grozema, F. C.; Houtepen, A. J.; Siebbeles, L. D. A.; Donegá, C. D. M. Radiative and Nonradiative Recombination in CuInS2 Nanocrystals and CuInS2-Based Core/Shell Nanocrystals. J. Phys. Chem. Lett. 2016, 7, 3503−3509.

[6] Fuhr, A.; Yun, H. J.; Crooker, S. A.; Klimov, V. I. Spectroscopic and Magneto-Optical Signatures of Cu1+ and Cu2+ Defects in Copper Indium Sulfide Quantum Dots. ACS Nano 2020, 14, 2212−2223.

[7] Ghosh, S.; Mandal, S.; Mukherjee, S.; De, C. K.; Samanta, T.; Mandal, M.; Roy, D.; Mandal, P. K. Near-Unity Photoluminescence Quantum Yield and Highly Suppressed Blinking in a Toxic-Metal-Free Quantum Dot. J. Phys. Chem. Lett. 2021, 12, 1426-1431.

[8] Ghosh, S.; Mukherjee, S.; Mandal, S.; De, C. K.; Mardanya, S.; Saha, A.; Mandal, P. K. Beneficial Intrinsic Hole Trapping and Its Amplitude Variation in a Highly Photoluminescent Toxic-Metal-Free Quantum Dot. J. Phys. Chem. Lett. 2023, 14, 260-266.

Acknowledgements:

Prasun Mandal and students involved in this work thank IISER Kolkata, SERB-DST, MoE-STARS, DST-INSPIRE, PMRF, UGC-India for financial help and instrumental facilities.

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