{"id":"94de3101-1d2c-45a9-811f-c13091c82950","arxiv_id":"2607.08889","paper_version":1,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":0,"one_line_summary":"Six diverse co-deposited organic-semiconductor glass mixtures are ultrastable at 0.78–0.88 Tg,mixture and their birefringence follows a simple iso-mobility average of the pure-component values.","lead":"Co-deposited 50:50 organic semiconductor glasses form ultrastable mixtures with low enthalpy even when the two components' glass-transition temperatures differ by more than 90 K. Their birefringence (molecular orientation) is predictable from the pure-component glasses via a surface-mobility mixing rule, giving practical design rules for longer-lived OLEDs.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified","rationale":"The reader correctly isolates the surface-mobility assumption as the weakest link and correctly judges that it does not rise to a correctness risk that would overturn the experimental findings. The manuscript already states the assumption explicitly, shows that Eq. 1 works while Eq. 2 fails, and restricts the claimed generality to systems that mix well and whose pure components form ultrastable glasses. The proposed surface-mobility measurement would be valuable future work but is not required to accept the present data set. Consequently the ACCEPT verdict stands.","tokens_in":16585,"tokens_out":392,"duration_ms":4411,"concrete_test":"Measure surface diffusion coefficients (or surface relaxation times) of each pure component and of one large-ΔTg mixture (e.g., DSA-Ph/Alq3) at the same absolute Tsub corresponding to 0.85 Tg,mixture; if the two species exhibit comparable surface mobility on the mixed film (within ~1 decade) while remaining disparate as pure films, the load-bearing inference is corroborated.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is well-supported by the six-mixture DSC and ellipsometry survey. The authors themselves flag the key inference (surface mobility of each species controlled by the single reduced temperature Tsub/Tg,mixture) and note that direct surface-mobility measurements on mixed films remain scarce. That inference is required for both ultrastability at large ΔTg and the derivation of Eq. 1, yet the data are internally consistent: Tonset/Tg and Tf/Tg match single-component benchmarks, the birefringence mixing rule (Eq. 1) outperforms the naïve same-Tsub average (Eq. 2), and the pure components are known to form ultrastable glasses. No internal inconsistency or unacknowledged experimental flaw is evident.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript reports a systematic DSC and spectroscopic-ellipsometry survey of six 50:50 co-deposited organic-semiconductor glass mixtures spanning large pure-component Tg differences (up to 96 K) and diverse molecular shapes. All six mixtures deposited at Tsub = 0.78–0.88 Tg,mixture exhibit ultrastable behavior (Tonset/Tg,mixture ≈ 1.04–1.06 and Tf/Tg,mixture ≈ 0.90–0.94) comparable to the best single-component PVD glasses. In addition, the birefringence of each mixture is quantitatively predicted by an iso-mobility weighted average of the pure-component birefringences (Eq. 1), which outperforms a naïve same-Tsub average (Eq. 2). The authors interpret both results via an extension of the surface-equilibration mechanism in which surface mobility of each species is controlled by the single reduced temperature Tsub/Tg,mixture.","tokens_in":16781,"tokens_out":884,"duration_ms":8648,"significance":"If the results hold, they establish that ultrastable co-deposited organic-semiconductor glasses are generic provided the pure components themselves form ultrastable glasses and mix well. This removes a prior practical restriction to small ΔTg and supplies a simple, parameter-free mixing rule for molecular orientation that is directly relevant to OLED host–guest layers and giant-surface-potential engineering. The breadth of the six-system survey, the direct calorimetric metrics, and the clear experimental discrimination between Eq. 1 and Eq. 2 constitute a solid empirical foundation that device designers can use immediately.","major_comments":[{"comment":"Discussion (paragraphs following Eq. 1) and SI §3: for DSA-Ph/Alq3 the liquid heat capacity and Tg,mixture are estimated rather than measured (crystallization intervenes). The authors report that the same estimation procedure recovers ΔCp of two other mixtures to within 10 %, corresponding to a ~2 % (~7 K) uncertainty in Tf. Because this pair supplies the largest ΔTg (96 K) and is therefore central to the “generic even at large ΔTg” claim, the manuscript should either (i) quantify how a ±7 K shift in Tf affects the placement of that point in Fig. 4B or (ii) supply an independent check (e.g., flash DSC or a lower-rate scan that avoids crystallization). Without that, the claim for ΔTg > 90 K rests on a single estimated data set.","section":null}],"minor_comments":[{"comment":"Figure 1F caption and SI §3: the procedure used to construct the liquid Cp line for DSA-Ph/Alq3 should be stated more explicitly in the main text so that a reader need not consult the SI to understand the gray curve.","section":null},{"comment":"Eq. 1 and surrounding text: the assumption that volume fraction equals weight fraction is stated but not justified; a brief note that densities of these organic semiconductors are typically within ~5 % of one another would suffice.","section":null},{"comment":"Figure 5: the gray dashed lines (Eq. 2) are difficult to distinguish from the black solid lines (Eq. 1) in some panels; a different line style or color would improve readability.","section":null},{"comment":"References: the recent surface-mobility study on mixed films (Zhang et al., J. Phys. Chem. B 2016) is cited, but a short sentence noting that direct surface-mobility data for the present semiconductor pairs remain unavailable would strengthen the Discussion.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The work is a natural and well-executed extension of the authors’ earlier TPD/m-MTDATA study. The six-system survey and the clean discrimination between Eqs. 1 and 2 make it suitable for a high-impact materials/soft-matter journal. The single estimated data set for DSA-Ph/Alq3 is the only load-bearing soft spot; once that uncertainty is quantified or mitigated, the paper is ready for acceptance."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This paper does exactly what the title promises. Cheng et al. take six chemically varied 50:50 organic-semiconductor pairs (ΔTg up to 96 K, rod/disk/sphere, polar/non-polar) and show that co-deposition at 0.78–0.88 Tg,mixture still produces the same kinetic and thermodynamic ultrastability we know from single-component PVD glasses (Tonset/Tg ≈ 1.05, Tf/Tg ≈ 0.90–0.94). They also give a parameter-free mixing rule (Eq. 1) that predicts mixture birefringence from the pure-component curves evaluated at the same reduced temperature; the naïve same-Tsub average fails for several pairs, so the iso-mobility construction is doing real work.\n\nWhat is new is the systematic reach. Earlier work (including their own 2023 TPD/m-MTDATA paper) stopped at small ΔTg or dilute guests. Here the claim is generic provided the pure components themselves form ultrastable glasses and mix well. The DSC and VASE data are clean, the comparison to liquid-cooled glasses is direct, and the authors flag the key inference—surface mobility of each species is controlled by the single reduced temperature Tsub/Tg,mixture—rather than hiding it. That inference is still untested by direct surface-mobility measurements on mixed films, but the internal consistency (stability metrics match the single-component benchmark; Eq. 1 beats Eq. 2) makes it a reasonable working hypothesis rather than a free parameter.\n\nSoft spots are minor and acknowledged: heat capacity and Tg for DSA-Ph/Alq3 are estimated, composition fluctuations produce shoulders in some DSC traces, and volume fraction is taken equal to weight fraction. None of these undercut the central results. Citation pattern is appropriate; self-citations are to the necessary prior measurements.\n\nThis is immediately useful for anyone designing OLED host–guest layers or thinking about surface equilibration in multicomponent glasses. It deserves a serious referee and a place in the literature. I would cite the design rules (choose mixture Tg ≈ 340–370 K for room-temperature deposition; use Eq. 1 for orientation) and bring it to reading group.","headline":"Solid experimental generalization: six diverse 50:50 mixtures show ultrastability and a clean birefringence mixing rule even at ΔTg ~ 96 K, with clear design rules for OLEDs.","tokens_in":17361,"tokens_out":568,"would_cite":true,"duration_ms":6640,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Co-deposited organic semiconductor glass mixtures form ultrastable glasses and have predictable anisotropic packing even when the pure-component glass-transition temperatures differ by more than 90 K.","keywords":["ultrastable glasses","physical vapor deposition","organic semiconductors","co-deposited mixtures","molecular orientation","birefringence","surface equilibration","OLED"],"falsifier":"Measure surface diffusion or surface relaxation times of each pure component on a series of co-deposited films whose overall Tg is fixed but whose composition is varied; if the two species retain very different surface mobilities when ΔTg is large, the ultrastability claim and the birefringence mixing rule both fail.","tokens_in":17496,"feed_emoji":"🔬","tokens_out":1030,"duration_ms":10936,"temperature":0.7,"pith_summary":"Organic electronic devices such as OLEDs rely on vapor-deposited mixtures of organic semiconductors as their active layers. The lifetime and efficiency of those devices depend on how stable the mixed glass is and how the molecules orient. This paper shows that six chemically diverse 50:50 binary mixtures, prepared by co-deposition at substrate temperatures near 0.85 times the mixture glass-transition temperature, all form ultrastable glasses: their kinetic stability and enthalpy are comparable to the best single-component vapor-deposited glasses, even when the two pure components have glass-transition temperatures that differ by nearly 100 K. At the same time, the optical birefringence of each mixture—which reports the average molecular orientation—can be calculated directly from the birefringence of the two pure glasses deposited under matching reduced-temperature conditions. The practical consequence is a simple design rule: choose components that each form ultrastable glasses on their own and that mix well; then both ultrastability and controllable molecular packing become generic features of the co-deposited film.","feed_headline":"Mixed organic glasses stay ultrastable even with 90 K Tg gaps","feed_subtitle":"Birefringence of co-deposited films is predicted from pure-component curves, guiding longer-lived OLEDs","key_machinery":"Surface equilibration on the growing film, extended so that the surface mobility of each species is controlled by the single reduced temperature Tsub/Tg,mixture; this common mobility both enables ultrastability at large ΔTg and supplies the iso-mobility averaging rule (Eq. 1) that predicts mixture birefringence from the pure-component curves.","core_discovery":"All six 50:50 co-deposited organic-semiconductor glass mixtures exhibit high kinetic stability (onset temperature roughly 1.05 times the mixture Tg) and substantially reduced enthalpy (fictive temperature 0.90–0.94 times the mixture Tg) when deposited at 0.78–0.88 times the mixture Tg, regardless of molecular shape or a pure-component Tg difference as large as 96 K. Simultaneously, the birefringence of each mixture is quantitatively given by a volume-weighted average of the pure-component birefringences evaluated at the same reduced temperature Tsub/Tg.","pith_inferences":["If surface mobility is truly composition-independent once reduced temperature is fixed, surface-diffusion experiments on mixed films should collapse onto a single master curve when plotted against T/Tg,mixture.","The same design rule should extend to ternary or higher-order co-deposited glasses provided every component can form an ultrastable glass alone and all components remain well mixed.","Device stacks that deliberately place the emitting layer at 0.85 Tg,mixture during deposition may systematically outlive otherwise identical stacks deposited far from that reduced-temperature window."],"forward_implications":["Any pair of organic semiconductors that individually form ultrastable glasses and that mix well will produce ultrastable 50:50 (and, by extension, dilute) co-deposited films near 0.85 Tg,mixture.","Birefringence—and therefore average molecular orientation—of a co-deposited mixture can be predicted a priori from the pure-component birefringence curves without additional measurements on the mixture.","For room-temperature deposition the most stable host–guest OLED layers are obtained when the host Tg lies near 340–370 K.","The same iso-mobility averaging should improve predictions of giant surface potential in polar/non-polar mixtures used for charge injection."],"fun_headline_variants":["Co-deposited organic glasses stay ultrastable despite 96 K Tg gaps","Mixture birefringence predicted from pure-component packing","All six 50:50 organic glass mixes form ultrastable films","Ultrastable mixed glasses form even with large Tg mismatches","Birefringence of co-deposited mixes follows pure-component average"],"cache_read_input_tokens":128,"weakest_assumption_plain":"The surface mobility of each molecule on the mixed film is set only by the single reduced temperature of the mixture, so both components share essentially the same surface relaxation time regardless of composition.","fun_headline_variants_meta":{"raw":{"variants":["Co-deposited organic glasses stay ultrastable despite 96 K Tg gaps","Mixture birefringence predicted from pure-component packing","All six 50:50 organic glass mixes form ultrastable films","Ultrastable mixed glasses form even with large Tg mismatches","Birefringence of co-deposited mixes follows pure-component average"]},"model":"grok-4.5","effort":"low","cost_usd":0.002944,"raw_usage":{"total_tokens":1098,"prompt_tokens":815,"num_sources_used":0,"completion_tokens":76,"cost_in_usd_ticks":29440000,"prompt_tokens_details":{"text_tokens":815,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":207,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":815,"tokens_out":76,"duration_ms":3482,"temperature":1.0,"reasoning_tokens":207,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-13T05:59:59.206687+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Measure surface diffusion or surface relaxation times of each pure component on a series of co-deposited films whose overall Tg is fixed but whose composition is varied; if the two species retain very different surface mobilities when ΔTg is large, the ultrastability claim and the birefringence mixing rule both fail.","supporting_citations":[],"review_version":1}