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Transient Photoluminescence with PS Resolution

A photoluminescence event occurs when an excited charge carrier decays emitting a photo. In inorganic semiconductors the photoluminescence process occurs between the conduction band minimum and valence band maximum, while in disordered semiconductors this process can occur between the HOMO and LUMO bands in a neat semiconductor or between a charge transfer state and a donor LUMO level in a blended film. Study of the photoluminescence brightness and lifetime can lead to insight into the chemical structure, quenching processes, and excited state dynamics. Furthermore; the lifetime of the photoluminescence process can provide insight into excited state dynamics of a semiconductor.

Our photoluminescence apparatus uses a Light Conversion-Pharos ps laser as a pump with outputs of 1030 nm, 515 nm, or 343 nm. This tunability allows us to pump a variety of semiconductors with bandgaps ranging across the visible spectrum. The steady state photoluminescence is collected using a Hamamatsu Photonic multichannel analyser (PMA) with sub nm resolution. The transient photoluminescence is collected using a Hamamatsu Streak Camera. The streak camera allows us to measure the transient photoluminescence with    < 5 ps resolution across the visible spectrum.

We use photoluminescence to study carrier lifetimes in neat and blended organic semiconductors, quenching of donor excitons in blended organic semiconductors, as well as the chemical environment and defect vacancies in inorganic semiconductors such as ZnO


Figure 1: Hamamatsu Streak Camera, with SpectraPro spectrograph, and collection optics.


Figure 2: (Large Panel) Wavelength and temporal resolved photoluminescence map collected with Hamamatsu Streak Camera. (Right Panel) transient photoluminescence signal integrated over the displayed spectrum. (Lower Panel) steady state photoluminescence signal integrated between pulses. 

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