A framework for extracting the rates of photophysical processes from biexponentially decaying photon emission data
Pith reviewed 2026-05-25 08:20 UTC · model grok-4.3
The pith
A model of reversible trapping into inactive states explains biexponential photoluminescence decay and extracts all transition rates without approximations.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Biexponential photoluminescence decay arises because carriers reversibly enter and leave optically inactive trap states whose dynamics are fully described by a closed linear rate-equation network; the network permits direct extraction of likelihood intervals for all transition rates, and supplies exact rate values when the high-temperature approximation holds.
What carries the argument
A closed linear rate-equation system coupling neutral excitons to reversible trapping and detrapping by optically inactive states.
If this is right
- All radiative, nonradiative, trapping, and release rates can be bounded by likelihood intervals from a single biexponential trace.
- In the high-temperature regime the model returns specific numerical values for every rate, outperforming reduced models used previously.
- The delayed photoluminescence component is directly attributable to the trapping-release cycle rather than to a second emissive species.
- The same rate values can be used to predict how photoluminescence efficiency changes with excitation density or temperature.
Where Pith is reading between the lines
- The approach could be tested by intentionally varying trap density through growth conditions and checking whether the extracted trapping rate scales proportionally.
- If the model holds, temperature-dependent measurements should show the trapping and release rates approaching each other as thermal energy increases.
- Extension to more complex heterostructures would require adding additional trap levels while preserving the linear-rate-equation structure.
Load-bearing premise
The observed biexponential photoluminescence decay is produced by reversible trapping into optically inactive states whose dynamics are completely captured by a closed set of linear rate equations.
What would settle it
A measured biexponential decay curve whose shape or temperature dependence cannot be reproduced by any choice of rates inside the four-state linear model, or whose extracted rates disagree with independent measurements of trap occupation times.
Figures
read the original abstract
There is strong interest in designing and realizing optically-active semiconductor nanostructures of greater complexity for applications in fields ranging from biomedical engineering to quantum computing. While these increasingly complex nanostructures can implement progressively sophisticated optical functions, the presence of more material constituents and interfaces also leads to increasingly complex exciton dynamics. In particular, the rates of carrier trapping and detrapping in complex heterostructures are critically important for advanced optical functionality, but they can rarely be directly measured. In this work, we develop a model that includes trapping and release of carriers by optically inactive states. The model explains the widely observed biexponential decay of the photoluminescence signal from neutral excitons in low dimensional semiconductor emitters. The model also allows determination of likelihood intervals for all the transition rates involved in the emission dynamics, without the use of approximations. Furthermore, in cases for which the high temperature limit is suitable, the model leads to specific values of such rates, outperforming reduced models previously used to estimate those quantities. We demonstrate the value of this model by applying it to time resolved photoluminescence measurements of CdSeTe/CdS heterostructures. We obtain values not only for the radiative and nonradiative lifetimes, but also for the delayed photoluminescence originating in trapping and release.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript develops a rate-equation framework incorporating reversible trapping and release of carriers into optically inactive states to model exciton dynamics in low-dimensional semiconductor nanostructures. It claims this closed linear system explains the widely observed biexponential photoluminescence (PL) decay from neutral excitons, enables extraction of likelihood intervals for all transition rates (radiative, nonradiative, trapping, release) without approximations, and in the high-temperature limit yields specific rate values that outperform reduced models. The framework is demonstrated on time-resolved PL data from CdSeTe/CdS heterostructures, providing values for the relevant rates including delayed PL contributions.
Significance. If the derivation and identifiability hold, the framework would be significant for the field, as it targets the extraction of trapping/detrapping rates that are critical for complex heterostructures but difficult to measure directly. The provision of likelihood intervals without approximations and the claimed superiority in the high-T limit, combined with application to experimental data, would represent a useful advance in analyzing biexponential PL signals.
major comments (3)
- [model development] The central assumption that biexponential PL decay is generated specifically by a minimal closed linear rate-equation system with reversible trapping into optically inactive states (model development section) is load-bearing for the claim that extracted intervals represent physical transition rates; if inhomogeneous broadening, additional states, or density-dependent processes contribute, the mapping from observed decay constants to microscopic rates is non-unique and the intervals lose their interpretation.
- [results] The assertion that the model outperforms reduced models and leads to specific rate values in the high-temperature limit (abstract and results section) requires explicit quantitative comparison, such as fit residuals, R² values, or error metrics between the full model and reduced models; without this, the superiority claim cannot be evaluated.
- [abstract] The claim of determining likelihood intervals for all rates without approximations (abstract) depends on the explicit fitting procedure and rate-equation solution; the manuscript must demonstrate how the biexponential parameters map to the full set of rates in a way that avoids circularity or hidden approximations in the likelihood construction.
minor comments (2)
- Notation for the transition rates (e.g., radiative vs. trapping) should be defined consistently in the main text with a clear table or diagram of the state diagram to aid readability.
- The abstract states the model 'explains' the decay; a brief discussion of why alternative biexponential generators were not considered would strengthen the presentation even if not central to the claims.
Simulated Author's Rebuttal
We thank the referee for their careful reading and constructive major comments. We address each point below and indicate the revisions that will be made to strengthen the manuscript.
read point-by-point responses
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Referee: [model development] The central assumption that biexponential PL decay is generated specifically by a minimal closed linear rate-equation system with reversible trapping into optically inactive states (model development section) is load-bearing for the claim that extracted intervals represent physical transition rates; if inhomogeneous broadening, additional states, or density-dependent processes contribute, the mapping from observed decay constants to microscopic rates is non-unique and the intervals lose their interpretation.
Authors: We agree that the extracted intervals are meaningful only under the stated model assumptions. The manuscript presents the framework as a minimal closed linear system capable of producing biexponential decay via reversible trapping; it does not claim this is the sole possible mechanism in all systems. In the revised manuscript we will expand the model development section to state the assumptions more explicitly and add a dedicated paragraph on limitations, including how inhomogeneous broadening, extra states, or density-dependent effects could render the mapping non-unique. This will clarify the conditions under which the reported intervals retain their physical interpretation. revision: yes
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Referee: [results] The assertion that the model outperforms reduced models and leads to specific rate values in the high-temperature limit (abstract and results section) requires explicit quantitative comparison, such as fit residuals, R² values, or error metrics between the full model and reduced models; without this, the superiority claim cannot be evaluated.
Authors: The referee correctly notes that quantitative metrics are required to substantiate the outperformance claim. The original text relied on the additional physical rates obtained and qualitative statements. We will revise the results section to include a direct comparison table (or supplementary figure) reporting fit residuals, R², and information criteria (e.g., AIC) for the full model versus the reduced models on the experimental CdSeTe/CdS datasets, thereby providing the requested quantitative evidence. revision: yes
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Referee: [abstract] The claim of determining likelihood intervals for all rates without approximations (abstract) depends on the explicit fitting procedure and rate-equation solution; the manuscript must demonstrate how the biexponential parameters map to the full set of rates in a way that avoids circularity or hidden approximations in the likelihood construction.
Authors: The mapping follows directly from the exact analytic solution of the linear rate equations, which yields closed-form relations between the observed biexponential amplitudes/decay constants and the four microscopic rates; the likelihood is then evaluated on these exact relations. No further approximations are introduced. To eliminate any ambiguity, the revised manuscript will add an explicit worked example (main text or supplementary information) that takes one fitted biexponential dataset, applies the algebraic mapping step by step, and constructs the likelihood intervals, thereby demonstrating transparency and absence of circularity. revision: yes
Circularity Check
No significant circularity; derivation is standard forward modeling from rate equations
full rationale
The paper constructs a closed linear rate-equation system (bright exciton plus optically inactive trap states) whose solution yields a biexponential form for the photoluminescence decay. Observed decay constants are then mapped to the microscopic rates via fitting or likelihood analysis. This is a conventional forward-modeling procedure in which the functional form is derived from the assumed Markov chain and the rates are outputs of the fit to data; no step reduces a claimed prediction to a fitted input by construction, nor does any load-bearing premise rest on self-citation. The abstract and model description contain no self-definitional relations, smuggled ansatzes, or uniqueness theorems imported from prior author work. The derivation remains self-contained against the experimental time-resolved PL traces.
Axiom & Free-Parameter Ledger
free parameters (1)
- transition rates (radiative, nonradiative, trapping, release)
axioms (1)
- domain assumption Carrier dynamics in the nanostructure are fully described by a closed linear system of rate equations that includes optically inactive trap states.
Reference graph
Works this paper leans on
-
[1]
our model allows us to understand clearly how the presence of a trapping state creates biexponential decay dynamics and 2) our model reduces to the well-known monoexponential behavior in the absence of the trapping state. Finally, given the biexponential decay of the exciton population shown by equation (4), the corresponding quantum yield can be written ...
-
[2]
H. Utzat, W. Sun, A. E. K. Kaplan, F. Krieg, M. Ginterseder, B. Spokoyny, N. D. Klein, K. E. Shulenberger, C. F. Perkinson, M. V. Kovalenko, and M. G. Bawendi, Science363, 1068 (2019), https://www.science.org/doi/pdf/10.1126/science.aau7392
-
[3]
H. Y. Ramírez, Y.-L. Chou, and S.-J. Cheng, Scientific Reports9, 1 (2019)
work page 2019
-
[4]
X. Ma, Y. Wang, J. Zide, and M. Doty, Phys. Rev. Applied13, 064029 (2020). 24
work page 2020
-
[5]
F. P. G. de Arquer, D. V. Talapin, V. I. Klimov, Y. Arakawa, M. Bayer, and E. H. Sargent, Science 373, eaaz8541 (2021), https://www.science.org/doi/pdf/10.1126/science.aaz8541
-
[6]
Q. Liu, Y. Sun, T. Yang, W. Feng, C. Li, and F. Li, Journal of the American Chemical Society 133, 17122 (2011), pMID: 21957992, https://doi.org/10.1021/ja207078s
-
[7]
J. Cotrino-Lemus and H. Y. Ramírez, Journal of Physics: Conference Series 864, 012081 (2017)
work page 2017
-
[8]
Y. Chen, S. Zhao, X. Wang, Q. Peng, R. Lin, Y. Wang, R. Shen, X. Cao, L. Zhang, G. Zhou, J. Li, A. Xia, and Y. Li, Journal of the American Chemical Society138, 4286 (2016), pMID: 26998730, https://doi.org/10.1021/jacs.5b12666
- [9]
-
[10]
C. C. Milleville, E. Y. Chen, K. R. Lennon, J. M. Cleveland, A. Kumar, J. Zhang, J. A. Bork, A. Tessier, J. M. LeBeau, D. B. Chase, J. M. O. Zide, and M. F. Doty, ACS Nano13, 489 (2019), https://doi.org/10.1021/acsnano.8b07062
-
[11]
M. Amani, D.-H. Lien, D. Kiriya, J. Xiao, A. Azcatl, J. Noh, S. R. Madhvapa- thy, R. Addou, S. KC, M. Dubey, K. Cho, R. M. Wallace, S.-C. Lee, J.-H. He, J. W. Ager, X. Zhang, E. Yablonovitch, and A. Javey, Science 350, 1065 (2015), https://www.science.org/doi/pdf/10.1126/science.aad2114
-
[12]
D. F. Macias-Pinilla and H. Y. Ramírez, Phys. Rev. A102, 033731 (2020)
work page 2020
-
[13]
Y. He, J. Yan, L. Xu, B. Zhang, Q. Cheng, Y. Cao, J. Zhang, C. Tao, Y. Wei, K. Wen, Z. Kuang, G. M. Chow, Z. Shen, Q. Peng, W. Huang, and J. Wang, Advanced Materials33, 2006302 (2021), https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202006302
-
[14]
W. BECKER, Journal of Microscopy 247, 119 (2012), https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2818.2012.03618.x
-
[15]
J. R. Lakowicz, chapter 4, in Principles of fluorescence spectroscopy (Springer, 2016) p. 141–142, 3rd ed
work page 2016
-
[16]
M. Jones, S. S. Lo, and G. D. Scholes, The Journal of Physical Chemistry C113, 18632 (2009), https://doi.org/10.1021/jp9078772
-
[17]
K. Gong, Y. Zeng, and D. F. Kelley, The Journal of Physical Chemistry C117, 20268 (2013), https://doi.org/10.1021/jp4065449
-
[18]
J. Zhang, X. Zhang, and J. Y. Zhang, The Journal of Physical Chemistry C113, 9512 (2009), 25 https://doi.org/10.1021/jp9026354
-
[19]
D. C. Hannah, N. J. Dunn, S. Ithurria, D. V. Talapin, L. X. Chen, M. Pelton, G. C. Schatz, and R. D. Schaller, Phys. Rev. Lett.107, 177403 (2011)
work page 2011
-
[20]
X. Li, Y. Wu, S. Zhang, B. Cai, Y. Gu, J. Song, and H. Zeng, Advanced Functional Materials 26, 2435 (2016), https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.201600109
- [21]
-
[22]
L. Y. Karachinsky, S. Pellegrini, G. S. Buller, A. S. Shkolnik, N. Y. Gordeev, V. P. Evtikhiev, and V. B. Novikov, Applied Physics Letters84, 7 (2004), https://doi.org/10.1063/1.1637962
-
[23]
Q. Wang, S. Stobbe, and P. Lodahl, Phys. Rev. Lett.107, 167404 (2011)
work page 2011
-
[24]
C. J. Bhongale, C.-W. Chang, C.-S. Lee, E. W.-G. Diau, and C.-S. Hsu, The Journal of Phys- ical Chemistry B109, 13472 (2005), pMID: 16852685, https://doi.org/10.1021/jp0502297
-
[25]
P. Coppens, J. Sokolow, E. Trzop, A. Makal, and Y. Chen, The Journal of Physical Chemistry Letters 4, 579 (2013), pMID: 26281869, https://doi.org/10.1021/jz400013b
- [26]
-
[27]
V. B. Verma, M. J. Stevens, K. L. Silverman, N. L. Dias, A. Garg, J. J. Coleman, and R. P. Mirin, Journal of Applied Physics109, 123112 (2011), https://doi.org/10.1063/1.3599889
-
[28]
H. Geng, Q. Liu, Y. Tang, and K. Wei, Photonics11, 10.3390/photonics11040358 (2024)
-
[29]
K. Oreszczuk, W. Pacuski, A. Rodek, M. Raczyński, T. Kazimierczuk, K. Nogajewski, T. Taniguchi, K. Watanabe, M. Potemski, and P. Kossacki, 2D Materials11, 025029 (2024)
work page 2024
-
[30]
W. M. Sanderson, J. Hoy, C. Morrison, F. Wang, Y. Wang, P. J. Morrison, W. E. Buhro, and R. A. Loomis, The Journal of Physical Chemistry Letters11, 3249 (2020), pMID: 32255643, https://doi.org/10.1021/acs.jpclett.0c00489
-
[31]
Z.Zhang, S.Zhang, I.Gushchina, T.Guo, M.C.Brennan, I.M.Pavlovetc, T.A.Grusenmeyer, and M. Kuno, The Journal of Physical Chemistry Letters12, 4024 (2021), pMID: 33880921, https://doi.org/10.1021/acs.jpclett.1c00811
-
[32]
E. Y. Chen, T. A. Welsch, J. M. Cleveland, C. C. Milleville, K. R. Lennon, H. Y. Ramírez, J. M. O. Zide, D. B. Chase, and M. F. Doty, The Journal of Physical Chemistry C125, 17183 (2021)
work page 2021
- [33]
- [34]
- [35]
-
[36]
X. Wu, M. T. Trinh, D. Niesner, H. Zhu, Z. Norman, J. S. Owen, O. Yaffe, B. J. Kudisch, and X.-Y. Zhu, Journal of the American Chemical Society137, 2089 (2015)
work page 2089
-
[37]
S. G. Motti, D. Meggiolaro, S. Martani, R. Sorrentino, A. J. Barker, F. De Angelis, and A. Petrozza, Advanced Materials 31, 1901183 (2019), https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201901183
- [38]
-
[39]
C. Hauswald, T. Flissikowski, T. Gotschke, R. Calarco, L. Geelhaar, H. T. Grahn, and O. Brandt, Phys. Rev. B88, 075312 (2013)
work page 2013
-
[40]
S. Krishnamurthy, A. Singh, Z. Hu, A. V. Blake, Y. Kim, A. Singh, E. A. Dolgopolova, D. J. Williams, A. Piryatinski, A. V. Malko, H. Htoon, M. Sykora, and J. A. Hollingsworth, ACS Nano 15, 575 (2021), pMID: 33381968, https://doi.org/10.1021/acsnano.0c05907
-
[41]
Z. Sabzevari, R. Sahraei, N. N. Jawhar, A. F. Yazici, E. Mutlugun, and E. Soheyli, Journal of Applied Physics129, 063107 (2021), https://doi.org/10.1063/5.0038696
-
[42]
R. Jain, R. Sinha, M. K. Sahu, and M. Jayasimhadri, Luminescence 36, 1444 (2021), https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/pdf/10.1002/bio.4085
-
[43]
Q. Chang, J. Sui, Z. Chai, and W. Wu, Nanomaterials11, 10.3390/nano11071761 (2021)
-
[44]
E. Soheyli, S. Zargoush, A. F. Yazici, R. Sahraei, and E. Mutlugun,54, 505110 (2021)
work page 2021
-
[45]
T. Berstermann, T. Auer, H. Kurtze, M. Schwab, D. R. Yakovlev, M. Bayer, J. Wiersig, C. Gies, F. Jahnke, D. Reuter, and A. D. Wieck, Phys. Rev. B76, 165318 (2007)
work page 2007
- [46]
-
[47]
A. J. Goodman, A. P. Willard, and W. A. Tisdale, Phys. Rev. B96, 121404(R) (2017)
work page 2017
-
[48]
C. Zhao, C. W. Tang, G. Cheng, J. Wang, and K. M. Lau,7, 115903 (2020)
work page 2020
-
[49]
G. Yang, M. Kazes, D. Raanan, and D. Oron, ACS Photonics 8, 1909 (2021), https://doi.org/10.1021/acsphotonics.1c00399
-
[50]
D. G. Sellers, J. Zhang, E. Y. Chen, Y. Zhong, M. F. Doty, and J. M. Zide, Solar Energy Materials and Solar Cells155, 446 (2016)
work page 2016
-
[51]
E. Y. Chen, C. Milleville, J. M. Zide, M. F. Doty, and J. Zhang, MRS Energy & Sustainability 27 5, E16 (2018)
work page 2018
-
[52]
E. Y. Chen, J. Zhang, D. G. Sellers, Y. Zhong, J. M. O. Zide, and M. F. Doty,Photovoltaic Specialist Conference, 1 (2015)
work page 2015
- [53]
-
[54]
N. Meir, I. Pinkas, and D. Oron, RSC Adv.9, 12153 (2019)
work page 2019
-
[55]
Z. Deutsch, O. Schwartz, R. Tenne, R. Popovitz-Biro, and D. Oron, Nano Lett.12, 2948 (2012)
work page 2012
- [56]
-
[57]
R. E. Bailey and S. Nie, J. Am. Chem. Soc.125, 7100 (2003)
work page 2003
-
[58]
L. Carbone, C. Nobile, M. De Giorgi, F. D. Sala, G. Morello, P. Pompa, M. Hytch, E. Snoeck, A. Fiore, I. R. Franchini, M. Nadasan, A. F. Silvestre, L. Chiodo, S. Kudera, R. Cingolani, R. Krahne, and L. Manna, Nano Letters 7, 2942 (2007), pMID: 17845067, https://doi.org/10.1021/nl0717661
-
[59]
D. V. Talapin, J. H. Nelson, E. V. Shevchenko, S. Aloni, B. Sadtler, and A. P. Alivisatos, Nano Letters 7, 2951 (2007), pMID: 17845068, https://doi.org/10.1021/nl072003g
-
[60]
D. Kim, Y. K. Lee, D. Lee, W. D. Kim, W. K. Bae, and D. C. Lee, ACS Nano11, 12461 (2017)
work page 2017
-
[61]
P. Reiss, M. Protière, and L. Li, Small 5, 154 (2009), https://onlinelibrary.wiley.com/doi/pdf/10.1002/smll.200800841
-
[62]
J. Cui, A. P. Beyler, L. F. Marshall, O. Chen, D. K. Harris, D. D. Wanger, X. Brokmann, and M. G. Bawendi, Nature Chemistry5, 602 (2013)
work page 2013
-
[63]
D. L. Ferreira, R. N. Maronesi, S. O. Ferreira, A. G. Silva, and M. A. Schiavon, The Journal of Physical Chemistry C123, 24289 (2019)
work page 2019
- [64]
-
[65]
J. E. Thomaz, K. P. Lindquist, H. I. Karunadasa, and M. D. Fayer, Journal of the American Chemical Society 142, 16622 (2020)
work page 2020
-
[66]
Y. Li, S. Natakorn, Y. Chen, M. Safar, M. Cunningham, J. Tian, and D. D.-U. Li, Frontiers in Physics 8, 10.3389/fphy.2020.576862 (2020)
-
[67]
A. F. van Driel, I. S. Nikolaev, P. Vergeer, P. Lodahl, D. Vanmaekelbergh, and W. L. Vos, Phys. Rev. B75, 035329. 28
-
[68]
Z. Gryczynski, I. Gryczynski, and J. R. Lakowicz, inMolecular Imaging, edited by A. Peri- asamy and R. N. Day (American Physiological Society, San Diego, 2005) pp. 21–56
work page 2005
-
[69]
R. Howl, C. Sabín, L. Hackermüller, and I. Fuentes, Journal of Physics B: Atomic, Molecular and Optical Physics51, 015303 (2017)
work page 2017
-
[70]
N. R. Fino, A. S. Camacho, and H. Y. Ramírez, Nanoscale Research Letters9, 297 (2014)
work page 2014
-
[71]
T. Ravindran, A. K. Arora, B. Balamurugan, and B. Mehta, Nanostructured Materials11, 603 (1999)
work page 1999
-
[72]
T. Brunhes, P. Boucaud, S. Sauvage, A. Lemaître, J.-M. Gérard, F. Glotin, R. Prazeres, and J.-M. Ortega, Phys. Rev. B61, 5562 (2000)
work page 2000
-
[73]
J. Jasieniak, L. Smith, J. van Embden, P. Mulvaney, and M. Califano, The Journal of Physical Chemistry C 113, 19468 (2009)
work page 2009
-
[74]
H. Y. Ramírez and A. Santana, Computer Physics Communications183, 1654 (2012)
work page 2012
-
[75]
J. Planelles, J. I. Climente, and C. Segarra, The Journal of Physical Chemistry C116, 25143 (2012)
work page 2012
-
[76]
H. Y. Ramírez, J. Flórez, and A. S. Camacho, Phys. Chem. Chem. Phys.17, 23938 (2015)
work page 2015
-
[77]
J. I. Climente, C. Segarra, and J. Planelles, New Journal of Physics15, 093009 (2013)
work page 2013
-
[78]
N. Aghoutane, L. Pérez, D. Laroze, M. El-Yadri, and E. Feddi, Results in Physics44, 106158 (2023)
work page 2023
- [79]
-
[80]
Population amplitudes The amplitudesA− X,A + X,AT, A− D, A+ D, A0 D, A0 D, A− G, A+ G and A0 G appearing in the time dependent population functions at equations (4), are given by the expressions A− X = 1 2−ΓPL + ΓXT−(ΓTX + ΓTD ) 2Γ2 , A+ X = 1 2 + ΓPL + ΓXT−(ΓTX + ΓTD ) 2Γ2 , AT = 4Γ2 0ΓXT [ ΓTD (Γ1−ΓTD )−Γ2 0 ] Γ2 [ Γ2 2 (Γ1−ΓTD )2− ( Γ1ΓTD−Γ2 1 + 2Γ0 )2...
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