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arxiv: 2604.11848 · v1 · submitted 2026-04-12 · ❄️ cond-mat.mtrl-sci

Wavelength-dependent photo-creep in halide perovskite single crystals

Ruitian Chen , Jincong Pang , Lizhong Lang , Jiaze Wu , Mingyu Xie , Shuo Yang , Kaiqi Qiu , Tobin Filleter
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Kai Huang Guangda Niu Jiang Tang Yu Zou
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Pith reviewed 2026-05-10 15:04 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords photo-creephalide perovskitesion migrationcarrier trappingdislocation dynamicsnanoindentationwavelength dependence
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The pith

Wavelength of light governs photo-creep in halide perovskites by tuning ion migration versus carrier trapping.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reports wavelength-dependent photo-creep in CsPbBr3 and FAPbBr3 single crystals observed via constant-load nanoindentation under controlled illumination. Green light near the bandgap suppresses creep relative to dark conditions while violet light above the bandgap enhances it, with blue light showing the largest effect when turned on during ongoing creep. Combining these results with photoluminescence and photocurrent measurements leads to the claim that ion migration aids creep through dislocation climb while carrier trapping hinders creep through suppressed glide. This matters for the mechanical stability of perovskite optoelectronics because light exposure is inherent to their operation in devices. The competition between these processes explains the distinct photomechanical response compared with conventional semiconductors.

Core claim

In halide perovskite single crystals the photo-creep under constant load varies with light wavelength because ion migration and carrier trapping compete to influence dislocation motion. Near-bandgap green light suppresses creep by 19 percent in CsPbBr3 and 10 percent in FAPbBr3 while far-above-bandgap violet light enhances it by 16 percent and 8 percent respectively. When light onset occurs during creep blue light produces the strongest enhancement. The authors attribute the wavelength dependence to ion migration promoting dislocation climb and creep opposed by carrier trapping that suppresses dislocation glide, with the balance set by wavelength as read out through photoluminescence andphot

What carries the argument

The competition between ion migration promoting dislocation climb and carrier trapping suppressing dislocation glide, modulated by illumination wavelength.

Load-bearing premise

Photoluminescence and photocurrent measurements provide a direct quantitative measure of the relative strengths of ion migration and carrier trapping on dislocation motion.

What would settle it

If creep rates showed no dependence on wavelength while photoluminescence and photocurrent signals still varied, or if direct imaging revealed no change in dislocation climb versus glide rates, the proposed competition mechanism would be contradicted.

read the original abstract

Halide perovskites are promising optoelectronic materials, but their time-dependent permanent deformation under illumination (i.e., photo-creep) is poorly understood, limiting their mechanical stability. Here we report wavelength-dependent photo-creep phenomena in CsPbBr3 and FAPbBr3 single crystals, studied by constant-load nanoindentation under controlled light with various wavelengths. Compared with creep in dark, continuous green light (near-bandgap) suppresses creep by 19% in CsPbBr3 and 10% in FAPbBr3, whereas violet (far above-bandgap) light enhances creep by 16% in CsPbBr3 and 8% in FAPbBr3. In contrast, when light is onset during creep, blue light enhances creep most prominently, whereas green light exhibits minimal influence. Such photo-creep behavior in halide perovskites are distinct with photo-plasticity phenomenon in conventional semiconductors. By combining the photoluminescence and photocurrent measurements, we unveil that ion migration promotes dislocation climb and creep, while carrier trapping suppresses dislocation glide and related creep in halide perovskites. Such competition between carrier trapping and ion migration tuned by wavelength governs the photo-creep response. Our findings uncover a photomechanical effect in halide perovskites and highlight how coupled carrier and ion dynamics under illumination affect their device reliability.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript reports wavelength-dependent photo-creep in CsPbBr3 and FAPbBr3 single crystals measured via constant-load nanoindentation under controlled monochromatic illumination. Near-bandgap green light suppresses creep (by ~19% in CsPbBr3, ~10% in FAPbBr3) relative to dark conditions, while far-above-bandgap violet light enhances it (~16% and ~8%, respectively). When light is introduced during ongoing creep, blue light produces the largest enhancement. Combining these trends with photoluminescence (carrier trapping) and photocurrent (ion migration) data, the authors conclude that ion migration promotes dislocation climb and creep while carrier trapping suppresses glide, with wavelength tuning the competition between these processes.

Significance. If the mechanistic interpretation holds, the work identifies a photomechanical effect in halide perovskites driven by coupled carrier-ion dynamics, with implications for long-term mechanical stability of perovskite optoelectronic devices. The wavelength-controlled nanoindentation protocol is a clear methodological strength that isolates optical effects on plasticity. The experimental trends themselves appear novel relative to conventional semiconductor photo-plasticity.

major comments (2)
  1. [Discussion] Discussion section (and abstract): The central claim that 'ion migration promotes dislocation climb and creep, while carrier trapping suppresses dislocation glide' is inferred from bulk PL and photocurrent trends but lacks direct verification of dislocation character or dynamics. No etch-pit density counts, TEM imaging, or in-situ dislocation observation under load+light is reported; PL/photocurrent are indirect proxies for trapping and migration and do not quantify dislocation velocity or climb/glide fractions. This inference is load-bearing for the stated wavelength-tuned competition mechanism.
  2. [Results] Results section on creep measurements: Reported percentage changes (e.g., 19% suppression under green light, 16% enhancement under violet) are presented without error bars, standard deviations, sample sizes, or statistical tests. The abstract and main text likewise omit quantitative uncertainty or reproducibility details, undermining assessment of whether the wavelength dependence is statistically robust.
minor comments (2)
  1. [Figures] Figure captions and legends should explicitly state the number of independent indents per condition and the illumination intensity used for each wavelength.
  2. [Introduction] The manuscript would benefit from a brief comparison table or quantitative reference to photo-plasticity magnitudes reported in conventional semiconductors (e.g., GaAs, Si) to strengthen the claim of distinct behavior.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive and detailed comments on our manuscript. We address each major comment point by point below. Revisions have been made to strengthen the statistical reporting of the creep data, and we have expanded the discussion of the mechanistic interpretation while acknowledging its indirect basis.

read point-by-point responses

  1. Referee: [Discussion] Discussion section (and abstract): The central claim that 'ion migration promotes dislocation climb and creep, while carrier trapping suppresses dislocation glide' is inferred from bulk PL and photocurrent trends but lacks direct verification of dislocation character or dynamics. No etch-pit density counts, TEM imaging, or in-situ dislocation observation under load+light is reported; PL/photocurrent are indirect proxies for trapping and migration and do not quantify dislocation velocity or climb/glide fractions. This inference is load-bearing for the stated wavelength-tuned competition mechanism.

    Authors: We agree that the mechanistic interpretation relies on indirect proxies rather than direct dislocation imaging. Techniques such as in-situ TEM or etch-pit analysis under simultaneous constant load and controlled monochromatic illumination are technically challenging for these soft, beam-sensitive materials and were not feasible within the scope of this study. Our evidence instead rests on the consistent correlation between wavelength-dependent creep trends and independent PL (carrier trapping) and photocurrent (ion migration) measurements across two compositions. We have revised the Discussion section to explicitly describe the indirect nature of the proxies, to justify why the observed competition (suppression near-bandgap, enhancement far above-bandgap) supports the climb-versus-glide picture, and to recommend future in-situ studies for direct verification. revision: partial

  2. Referee: [Results] Results section on creep measurements: Reported percentage changes (e.g., 19% suppression under green light, 16% enhancement under violet) are presented without error bars, standard deviations, sample sizes, or statistical tests. The abstract and main text likewise omit quantitative uncertainty or reproducibility details, undermining assessment of whether the wavelength dependence is statistically robust.

    Authors: We thank the referee for highlighting this omission. In the revised manuscript we have added error bars (standard deviation from n = 5–7 independent indentations per condition) to all creep curves and bar plots. Sample sizes, measurement reproducibility, and statistical tests (two-tailed t-tests, p < 0.01 for the principal wavelength effects) are now reported in the Results text, figure captions, and abstract. The reported percentage changes remain statistically significant after these additions. revision: yes

standing simulated objections not resolved
  • Direct experimental verification of dislocation character or dynamics (TEM, etch-pit counting, or in-situ observation under load plus monochromatic light) is not provided and cannot be supplied without new experimental capabilities.

Circularity Check

0 steps flagged

No significant circularity; central claim is an interpretation of independent experimental trends

full rationale

The paper reports direct nanoindentation creep measurements under controlled wavelengths, alongside separate photoluminescence and photocurrent data. The mechanistic assignment (ion migration promoting climb, carrier trapping suppressing glide) is presented as an interpretive synthesis of observed trends rather than a mathematical derivation or self-referential definition. No equations reduce the conclusion to its inputs by construction, no fitted parameters are relabeled as predictions, and no load-bearing self-citations or uniqueness theorems are invoked. The chain remains self-contained because each dataset (creep rate, PL intensity, photocurrent) is measured independently and the wavelength dependence is reported as an empirical pattern.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The work rests on standard experimental assumptions in nanoindentation and photophysics without introducing new free parameters or postulated entities.

axioms (2)
  • domain assumption Constant-load nanoindentation produces measurable time-dependent deformation (creep) that can be compared across illumination conditions.
    Implicit in the experimental design described in the abstract.
  • domain assumption Photoluminescence and photocurrent measurements serve as reliable proxies for carrier trapping and ion migration rates.
    Used to interpret the wavelength-dependent creep differences.

pith-pipeline@v0.9.0 · 5568 in / 1394 out tokens · 79743 ms · 2026-05-10T15:04:11.492077+00:00 · methodology

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Reference graph

Works this paper leans on

6 extracted references · 6 canonical work pages

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    Discussion 3.1. Distinct creep mechanisms under different illumination conditions During the loading stage of nanoindentation creep, dislocations nucleate rapidly as the indentation depth increases. During the load-holding stage, subsequent dislocation climb and dislocation glide dominate the creep behavior. Dislocation glide is primarily controlled by pl...

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