{"id":"275a5920-4ad7-4e97-9b9e-1b10c881f1a6","arxiv_id":"2411.16576","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"Applying a voltage to a WSe2 monolayer tunneling junction switches its carrier doping and changes which excitonic complexes emit light, while electrical excitation yields broader emission than laser excitation.","lead":"This paper measures how light emitted from a WSe2 monolayer inside a vertical tunneling device changes when an external voltage is applied. It shows that bias can switch the material between electron-rich and hole-rich states, and that electrical and laser excitation produce different emission spectra.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Excitonic peak assignments are load-bearing and rest solely on literature energy alignment; a misidentification would invalidate the claimed carrier-concentration control and PL/EL mechanism difference.","rationale":"The paper's strongest claim is that bias voltage controls the sign and value of free carriers in the WSe2 monolayer. The only evidence for this is the appearance and disappearance of charged and neutral excitonic complexes in the PL spectra. If the spectral labels are wrong, the entire physical narrative—including the location of the charge neutrality point at 1.04 V and the assertion that PL and EL probe different excitation regimes—collapses. The authors themselves acknowledge the T−′ assignment is still debated, highlighting the fragility of the label-based inference. The reader's weakest assumption identified exactly this point, and I agree. The proposed magneto-optical check is decisive because each proposed complex has a characteristic Zeeman g-factor and polarization selection rule that can be measured directly and compared to established values. This is a standard technique used in the very references the paper cites, and it would remove the circularity of relying on literature energy positions without accounting for this device's specific environment. The central observation—voltage-dependent PL and EL—is likely correct, so rejection is not warranted; however, the verification is essential, making conditional acceptance appropriate. Thus the reader's verdict remains unchanged.","tokens_in":10651,"tokens_out":6055,"duration_ms":54432,"concrete_test":"Perform polarization- and magnetic-field-resolved PL measurements on the same device under identical bias conditions. Record σ+ and σ− PL spectra at B = 0 T and B = 9 T applied perpendicular to the WSe2 monolayer. For each annotated line (X0, T+, T−, D0, D+, D−, XX0, XX−, T−′), extract the circular polarization degree and the Zeeman splitting. Compare the measured g-factors and selection rules with literature values for bright neutral/charged excitons in hBN-encapsulated WSe2 (e.g., |g| ≈ 4 for X0) and for dark excitons, which typically become visible only via phonon assistance or under magnetic field with distinct g-factors. If the measured g-factors and polarization patterns match the proposed assignments, the identification is confirmed.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that bias voltage changes the sign and value of free carrier concentrations is inferred entirely from the identification of excitonic complexes (X0, T+, T−, T−S, D0, D+, D−, XX0, XX−, T−′) in the PL spectra. The assignments are made 'according to the energy positions of excitonic complexes reported in the literature' (Section 3, first paragraph), with no independent verification such as polarization, magneto-optical, or excitation-power-dependent measurements. In this specific vertical tunneling device, the WSe2 monolayer experiences an out-of-plane electric field, non-uniform dielectric screening (hBN barriers of 7 and 3 layers on the two sides), and possible strain from the stacked assembly, all of which can shift excitonic energies by several meV and even reorder the apparent levels. The identification of the charge neutrality point at 1.04 V relies on the appearance of XX0; if the XX0 label is wrong (e.g., it is actually a phonon replica or a localized state), the claimed carrier sign change is not established. Similarly, the T−′ line is explicitly stated to be 'still under debate' (Refs. [19,35]), yet it is used to infer large electron density. Since the entire narrative of carrier-concentration control and the difference between PL and EL mechanisms rests on these labels, the peak assignment is the most load-bearing assumption.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports low-temperature (5 K) photoluminescence (PL) and electroluminescence (EL) studies of a WSe2 monolayer embedded in asymmetric hBN tunneling barriers between graphene electrodes. The authors present voltage-dependent PL maps in which they identify ten excitonic complexes, and they infer that the bias voltage tunes both the sign and magnitude of the free-carrier concentration, with a charge neutrality point at 1.04 V. EL is observed for |Vb| > 3.5 V, is attributed to recombination in high-carrier-density regimes, and is argued to arise from excitation mechanisms different from those in PL.","tokens_in":10927,"tokens_out":4702,"duration_ms":40484,"significance":"The device geometry and the voltage-dependent PL/EL data are of interest to the 2D materials and optoelectronics community, and the raw data are made available through a DOI. The observation of bias-tunable emission features and the comparison between PL and EL in the same device are valuable. The manuscript also openly acknowledges the debated nature of the T−′ line and the possibility of sample heating, which is commendable. However, the central claim of carrier-concentration control is inferred entirely from peak assignments that are taken from the literature without independent verification in this device, and the paper does not provide error bars or control experiments. If the assignments are correct, the conclusions are plausible; the lack of independent confirmation is the main weakness.","major_comments":[{"comment":"The identification of the emission lines (X0, T+, T−T, T−S, D0, D+, D−, XX0, XX−, T−′) is made solely by matching energy positions to literature values, as stated in the first paragraph of Section 3. No polarization-resolved, magneto-optical, or excitation-power-dependent measurements are provided to confirm the assignments. Because the claimed bias-induced change of carrier sign and concentration is inferred entirely from these labels, a shift in any transition energy due to the out-of-plane electric field, the asymmetric dielectric environment (7-layer and 3-layer hBN), or strain could change the interpretation. Please provide additional verification or quantitatively estimate the expected energy shifts in this device.","section":"Section 3, first paragraph"},{"comment":"The charge neutrality point is identified at 1.04 V solely from the appearance of the XX0 line in the PL spectrum. If the XX0 label is incorrect (e.g., a phonon replica or a localized state), the claim that the doping changes sign at this voltage is not established. The authors should justify this assignment with independent evidence, such as a transport measurement or a gate-dependent study in the same device.","section":"Section 3, charge neutrality point"},{"comment":"The T−′ line, which is used to infer large electron densities under negative bias, is stated to be 'still under debate' (Refs. [19,35]). Relying on an unassigned feature as evidence for a high-doping regime is load-bearing for the conclusion of bias-tunable carrier concentration; the authors should either provide a firmer identification (e.g., via magneto-optical measurements) or temper the claim that the electron density is 'large'.","section":"Section 3, T−′ line"}],"minor_comments":[{"comment":"The phrase 'hexagonal boron nitrade' should be 'hexagonal boron nitride'.","section":"Section 2.1"},{"comment":"'Both restuls are presented' should be 'Both results are presented'.","section":"Figure 4 caption"},{"comment":"'high career concentration regimes' should be 'high carrier concentration regimes'.","section":"Conclusions"},{"comment":"The title 'Elektroluminescent devices' should be 'Electroluminescent devices'.","section":"Reference [38]"},{"comment":"The author name 'Kfelina' appears to be a typo; please check the spelling.","section":"Reference [33]"},{"comment":"The statement 'The colour scale represents the PL and EL intensity' does not specify whether the scale is linear or logarithmic, nor the units; please clarify.","section":"Figure 2 caption"},{"comment":"The peak positions and the charge neutrality point are quoted without error bars; please provide uncertainties for the extracted values.","section":"Section 3"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is within the scope of the journal, and the experimental data appear to be of good quality. The main concern is the reliance on literature-based peak assignments without independent verification; this is a common issue in the field, but here it is load-bearing because the entire narrative of carrier-concentration tuning depends on it. If the authors can provide additional evidence (or at least a careful quantitative discussion of expected shifts), the paper would be much stronger. The data availability statement is a positive aspect."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You should know two things about this paper up front. First, it is a clean, workmanlike experimental report on a WSe2 vertical tunneling LED: voltage-dependent PL and EL maps at 5 K, asymmetric hBN thickness, a charge neutrality point at 1.04 V, and a stack of excitonic features that the authors assign using literature energy positions. Second, the central qualitative claim, that bias voltage tunes the sign and value of free carrier concentration, is very likely correct, even though the evidence for it is entirely based on spectral line identification rather than any independent doping probe.\n\nWhat is genuinely new is the specific device geometry, asymmetric 7-layer/3-layer hBN barriers, and the accompanying bias-dependent PL and EL data. The paper also ships raw data at a DOI, which is good practice. The observation that EL requires higher bias than the neutral exciton energy, and that EL appears in a high-carrier regime with broad many-body features, is consistent with earlier work but documented here for a new structure. The IV curve and its three-step interpretation are clearly labeled as tentative, which is honest.\n\nThe soft spots are proportionate. The stress-test concern about peak assignments is fair but less load-bearing than it looks. The energy spacing between positive and negative trions in hBN-encapsulated WSe2 is large (tens of meV), and the field has multiple independent measurements of these levels. A single mislabeled line would not overturn the direction of the doping trend. That said, the specific claim that the charge neutrality point is exactly 1.04 V rests on identifying XX0, and the T−' line is admittedly under debate, so the paper would benefit from power-dependent or polarization measurements, or at least an explicit statement that the assignments are literature-based and could be affected by local strain or field. The absence of error bars on peak positions and the neutrality point is a real weakness, but minor for this type of study.\n\nThe bigger issue is rhetorical: the abstract and conclusion say the results \"prove\" that PL and EL excitation mechanisms are \"completely different.\" The data show they are different, but prove and completely are stronger than the evidence supports. The EL spectral assignments to many-body complexes are also somewhat speculative, and the paper acknowledges possible heating as an alternative explanation.\n\nOverall, this is a competent paper that will be useful to people working on TMD-based light-emitting devices. It does not open a new direction, and the conclusions are not surprising, but the data are new, the device is well characterized, and the paper is coherent on its own terms. I would send it to review, with advice to soften the claims and add error estimates. It deserves referee time.","headline":"A solid, careful device study with standard exciton assignments; the main weaknesses are overstatement of the PL/EL mechanism difference and missing error bars, but it deserves serious review.","tokens_in":11458,"tokens_out":1602,"would_cite":true,"duration_ms":18163,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"A bias voltage sweeps a WSe2 monolayer from n- to p-type doping, switching its emission between negatively and positively charged exciton complexes.","keywords":["WSe2","monolayer","vertical tunneling junction","electroluminescence","photoluminescence","excitonic complexes","trions","charge neutrality point"],"falsifier":"A magneto-optical or polarization-resolved measurement of the same device at fixed bias would settle the assignments: each claimed complex has a characteristic valley Zeeman splitting and circular-polarization selection rule, so an absence of the predicted shifts or selection rules would show that the energy-matching identification is not valid. Alternatively, independently gating the same WSe2 monolayer and comparing the bias-driven PL sequence would test whether the voltage indeed acts as a pure carrier-density knob.","tokens_in":10506,"feed_emoji":"💡","tokens_out":5885,"duration_ms":48830,"temperature":0.7,"pith_summary":"This paper reports that a vertical tunneling junction built around a single WSe2 monolayer can be driven by bias voltage through the whole range of carrier doping: from an n-type regime with excess electrons, through a charge neutrality point, to a p-type regime with excess holes. The voltage-dependent photoluminescence maps out the resulting excitonic complexes, with negatively charged species dominating at negative bias and positively charged species at positive bias. At high bias, electroluminescence appears and is attributed to recombination in a high-carrier-density regime, with spectra broadened partly by current-induced heating. The authors conclude that photoluminescence and electroluminescence excite carriers through different mechanisms, so the two techniques see different emission channels.","feed_headline":"Bias voltage flips a WSe2 monolayer between n- and p-type emission","feed_subtitle":"Voltage replaces electrostatic gates to map every exciton state in one WSe2 monolayer.","key_machinery":"The central object is the vertical tunneling junction itself: a WSe2 monolayer encapsulated between hBN barriers of 7 and 3 layers and sandwiched between two graphene electrodes. Its action is voltage-controlled carrier doping via tunneling through the asymmetric barriers. The identification of each excitonic complex in the bias-dependent PL relies on comparing peak energy positions with spectra of hBN-encapsulated WSe2 monolayers reported in the literature, and the EL interpretation relies on the current-voltage characteristics together with earlier WSe2 tunneling light-emitting devices.","core_discovery":"The central claim is that in an hBN-encapsulated WSe2 monolayer contacted by graphene electrodes, an applied bias voltage acts as a continuous carrier-density knob: lowering the voltage raises the free-electron concentration and favors negatively charged complexes (negative trions, negative biexciton, dark negative trion, and the debated T−' line), while raising it depletes electrons, crosses the charge neutrality point at about 1.04 V, and then injects holes, producing positive trions and a dark positive trion. The same device emits electroluminescence above roughly ±3.5 V, with asymmetric spectra for the two polarities due to the asymmetric hBN barrier thicknesses (7 layers bottom, 3 layers top). The EL bands at high bias are assigned to many-body recombination of a single charge carrier with a sea of opposite carriers, and their broadening is partly attributed to Joule heating. Because the PL and EL spectra show different complexes, the paper argues that optical and electrical excitation produce different carrier populations and recombination channels.","pith_inferences":["If the voltage-doping correspondence is as clean as reported, this geometry could become a gate-free route to map doping-dependent exciton physics in other transition-metal dichalcogenide monolayers.","The T−' line, which appears only at high electron density and whose origin is still under debate, could be identified by measuring its valley polarization or magnetic-field splitting in the same device; the paper does not report such a measurement.","Extending the bias range or reducing barrier thickness could reveal whether the missing high-bias step in the negative-voltage electroluminescence is truly absent or simply requires larger voltages than used here.","The same device could test whether the electroluminescence threshold can be lowered toward the neutral exciton energy by improving contacts, since the paper attributes the high threshold to contact imperfections and the thick bottom hBN barrier."],"forward_implications":["A single WSe2 device can serve as a continuously tunable source of n- and p-type excitonic complexes, with the charge neutrality point located at a known bias of 1.04 V.","The presence of both bright and dark charged excitons means voltage-controlled tunneling structures can access recombination channels that are usually dark in photoluminescence.","The asymmetric hBN barriers make positive and negative bias regimes behave differently, so engineering barrier thickness could tune the electroluminescence threshold and intensity.","At high bias, many-body recombination and Joule heating dominate the electroluminescence, so carrier-density and thermal effects must be separated in any future device analysis.","Because photoluminescence and electroluminescence probe different carrier regimes, combined measurements give a more complete picture of excitonic complexes than either technique alone."],"supporting_citations":[{"why":"Supplies the reference framework for identifying dark-exciton and charged-exciton lines in hBN-encapsulated WSe2 monolayers.","marker":"[41]"},{"why":"Provides the experimental and theoretical basis for the charged-exciton (trion) assignments and their binding energies.","marker":"[9]"},{"why":"Supports the identification of biexciton complexes and their voltage-dependent behavior.","marker":"[4]"},{"why":"Supports the assignment of intervalley dark excitons and dark trions in the PL spectra.","marker":"[24]"},{"why":"Supports the appearance of the T−' line in the high-electron-density regime.","marker":"[19]"},{"why":"Provides the comparison for the broad electroluminescence spectra attributed to high-carrier-density many-body recombination.","marker":"[40]"},{"why":"Supports the tunneling mechanism and the interpretation of electroluminescence from hBN-based vertical tunneling junctions.","marker":"[11]"},{"why":"Supports the discussion of electroluminescence threshold and sub-bandgap voltage operation in WSe2 heterostructures.","marker":"[6]"}],"fun_headline_variants":["Bias voltage tunes a WSe2 monolayer through every exciton state","One monolayer, all excitons: bias voltage maps emission","Voltage dials free carriers in WSe2, changing emitted light","WSe2 junction: bias voltage flips from electron to hole emission","Bias voltage controls exciton zoo in a single WSe2 layer"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The entire assignment of emission lines to specific excitonic complexes rests on matching their energy positions to published spectra of other hBN-encapsulated WSe2 monolayers; if strain, the dielectric environment, or the applied field shifts any of these levels in this device, the claimed doping dependence of the complexes would be wrong.","fun_headline_variants_meta":{"raw":{"variants":["Bias voltage tunes a WSe2 monolayer through every exciton state","One monolayer, all excitons: bias voltage maps emission","Voltage dials free carriers in WSe2, changing emitted light","WSe2 junction: bias voltage flips from electron to hole emission","Bias voltage controls exciton zoo in a single WSe2 layer"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000725,"raw_usage":{"total_tokens":3231,"prompt_tokens":905,"completion_tokens":2326,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":521,"completion_tokens_details":{"reasoning_tokens":2233}},"tokens_in":521,"tokens_out":2326,"duration_ms":23440,"temperature":1.0,"reasoning_tokens":2233,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T12:57:19.634372+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A magneto-optical or polarization-resolved measurement of the same device at fixed bias would settle the assignments: each claimed complex has a characteristic valley Zeeman splitting and circular-polarization selection rule, so an absence of the predicted shifts or selection rules would show that the energy-matching identification is not valid. Alternatively, independently gating the same WSe2 monolayer and comparing the bias-driven PL sequence would test whether the voltage indeed acts as a pure carrier-density knob.","supporting_citations":[{"cited_title":"TheeffectofdielectricenvironmentonthebrighteningofneutralandchargeddarkexcitonsinWSe2monolayer","cited_arxiv_id":null,"evidence_quote":"Supplies the reference framework for identifying dark-exciton and charged-exciton lines in hBN-encapsulated WSe2 monolayers."},{"cited_title":"Charged excitons in monolayerwse2: Experiment and theory","cited_arxiv_id":null,"evidence_quote":"Provides the experimental and theoretical basis for the charged-exciton (trion) assignments and their binding energies."},{"cited_title":"Charge-tuneable biexciton complexes in monolayer wse2","cited_arxiv_id":null,"evidence_quote":"Supports the identification of biexciton complexes and their voltage-dependent behavior."},{"cited_title":"Multipathopticalrecombination of intervalley dark excitons and trions in monolayerwse2","cited_arxiv_id":null,"evidence_quote":"Supports the assignment of intervalley dark excitons and dark trions in the PL spectra."},{"cited_title":"Many-body exciton and inter-valley correlations in heavily electron-dopped wse2 monolayers","cited_arxiv_id":null,"evidence_quote":"Supports the appearance of the T−' line in the high-electron-density regime."},{"cited_title":"Electroluminescence from pure resonant states in hbn-based vertical tunneling junctions","cited_arxiv_id":null,"evidence_quote":"Supports the tunneling mechanism and the interpretation of electroluminescence from hBN-based vertical tunneling junctions."},{"cited_title":"Nano Letters 17, 1425–1430","cited_arxiv_id":null,"evidence_quote":"Supports the discussion of electroluminescence threshold and sub-bandgap voltage operation in WSe2 heterostructures."}],"review_version":1}