Urbach tail
E484703
The Urbach tail is an exponential absorption edge observed in the optical spectra of disordered or amorphous semiconductors, reflecting localized states and disorder in the material’s band structure.
All labels observed (2)
| Label | Occurrences |
|---|---|
| Urbach rule | 1 |
| Urbach tail canonical | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T4975883 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: Urbach tail Context triple: [Electronic Processes in Non-Crystalline Materials, describedConcept, Urbach tail]
-
A.
Stokes shift
Stokes shift is a phenomenon in spectroscopy where the wavelength of emitted light is longer (lower energy) than that of the absorbed light, commonly observed in fluorescence and phosphorescence.
-
B.
Shockley–Queisser limit
The Shockley–Queisser limit is a theoretical maximum efficiency for single-junction solar cells, defining the upper bound on how much sunlight can be converted into electricity under standard conditions.
-
C.
Esaki diode
The Esaki diode is a heavily doped semiconductor tunnel diode that exhibits negative differential resistance, enabling high-speed and microwave-frequency electronic applications.
-
D.
Franck–Condon principle
The Franck–Condon principle is a rule in molecular spectroscopy that explains the intensity distribution of vibronic transitions by assuming electronic transitions occur much faster than nuclear motion, making vertical transitions between vibrational states most probable.
-
E.
Stark effect
The Stark effect is the splitting and shifting of atomic or molecular spectral lines caused by an external electric field.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: Urbach tail Target entity description: The Urbach tail is an exponential absorption edge observed in the optical spectra of disordered or amorphous semiconductors, reflecting localized states and disorder in the material’s band structure.
-
A.
Stokes shift
Stokes shift is a phenomenon in spectroscopy where the wavelength of emitted light is longer (lower energy) than that of the absorbed light, commonly observed in fluorescence and phosphorescence.
-
B.
Shockley–Queisser limit
The Shockley–Queisser limit is a theoretical maximum efficiency for single-junction solar cells, defining the upper bound on how much sunlight can be converted into electricity under standard conditions.
-
C.
Esaki diode
The Esaki diode is a heavily doped semiconductor tunnel diode that exhibits negative differential resistance, enabling high-speed and microwave-frequency electronic applications.
-
D.
Franck–Condon principle
The Franck–Condon principle is a rule in molecular spectroscopy that explains the intensity distribution of vibronic transitions by assuming electronic transitions occur much faster than nuclear motion, making vertical transitions between vibrational states most probable.
-
E.
Stark effect
The Stark effect is the splitting and shifting of atomic or molecular spectral lines caused by an external electric field.
- F. None of above. chosen
Statements (48)
| Predicate | Object |
|---|---|
| instanceOf |
absorption edge
ⓘ
optical phenomenon ⓘ solid-state physics concept ⓘ |
| appearsBelow | fundamental absorption edge ⓘ |
| associatedWith |
sub-bandgap absorption
ⓘ
tail states in band gap ⓘ |
| characterizedBy |
Urbach energy
ⓘ
slope of exponential absorption tail ⓘ |
| dependsOn |
electron-phonon coupling
ⓘ
structural disorder ⓘ temperature ⓘ |
| describes | exponential absorption edge ⓘ |
| hasAlternativeName |
Urbach energy tail
ⓘ
Urbach rule ⓘ
linked to:
Urbach tail
|
| hasDiscoveryBy | Franz Urbach ⓘ |
| hasDiscoveryYear | 1953 ⓘ |
| hasDomain |
condensed matter physics
ⓘ
materials science ⓘ semiconductor physics ⓘ |
| hasMathematicalForm | exponential dependence of absorption coefficient on photon energy ⓘ |
| indicates | degree of disorder in a semiconductor ⓘ |
| influences |
device efficiency in optoelectronics
ⓘ
optical losses in solar cells ⓘ sub-bandgap absorption in LEDs ⓘ |
| measuredBy |
optical absorption spectroscopy
ⓘ
photoluminescence spectroscopy analysis ⓘ photothermal deflection spectroscopy ⓘ |
| modeledBy | exponential law for absorption coefficient ⓘ |
| occursIn |
amorphous semiconductors
ⓘ
crystalline semiconductors with disorder ⓘ disordered semiconductors ⓘ optical absorption spectra ⓘ semiconductors ⓘ |
| relatedTo |
band edge absorption
ⓘ
disorder in solids ⓘ electronic band structure ⓘ localized electronic states ⓘ phonon interactions ⓘ temperature-dependent absorption ⓘ |
| relevantTo |
amorphous silicon
ⓘ
chalcogenide glasses ⓘ organic semiconductors ⓘ perovskite semiconductors ⓘ |
| usedIn |
analysis of amorphous materials
ⓘ
characterization of optical quality of semiconductors ⓘ evaluation of defect density in semiconductors ⓘ optoelectronic device optimization ⓘ photovoltaic material characterization ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: Urbach tail Description of subject: The Urbach tail is an exponential absorption edge observed in the optical spectra of disordered or amorphous semiconductors, reflecting localized states and disorder in the material’s band structure.
Referenced by (2)
Full triples — surface form annotated when it differs from this entity's canonical label.
linked to: Urbach tail