Quantum Dot Photoluminescence Quantum Yield

Quantum Dot Ensemble

Surface trap density 40%

Temperature 300 K

Excitation pump rate 0.08 / ns

Live Photophysics

radiativenon-radiative

Quantum yield Φ (measured)

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Quantum yield Φ (theory)

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Lifetime τ (measured)

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Photon emission rate

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How it works

Each dot models a two-level exciton: after excitation, its energy leaves through two competing first-order pathways — a radiative recombination (rate k_r, emits a photon) and a non-radiative pathway through surface trap states or phonon coupling (rate k_nr, releases heat). The photoluminescence quantum yield is the fraction of decays that emit a photon:

Φ = k_r / (k_r + k_nr)
τ = 1 / (k_r + k_nr)   (fluorescence lifetime)

Non-radiative trapping has two independent contributions modeled here:

k_nr = D_trap · k_trap,max · S_shell  +  A · exp(−E_a / k_B T)

The first term is capture by unpassivated surface dangling bonds — proportional to trap density D_trap and suppressed by a factor S_shell (≈0.05) once an epitaxial ZnS shell passivates the surface, exactly as in real CdSe/ZnS core–shell quantum dots. The second term is thermally activated (Arrhenius) phonon-assisted trapping over an activation barrier E_a, which is why quantum dot photoluminescence dims as temperature rises.

Surface trap density — sets how many unpassivated surface states compete with radiative recombination.
Temperature — raises the thermally activated non-radiative rate via the Arrhenius term.
ZnS Shell Passivation — toggles an inorganic shell that buries surface traps, the standard real-world fix for dim colloidal quantum dots.
Pump rate — how often ground-state dots are re-excited; it changes brightness/sparkle rate but not Φ itself, since Φ depends only on the rate ratio.

Each glowing sphere is one dot running its own stochastic exponential decay clock, so the bar and readouts on the left are a genuine running measurement over the visible ensemble — not a canned number.

Ground state Excited exciton Radiative photon Non-radiative (heat)

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