Photoluminescence (PL) in Organic Materials скачать в хорошем качестве

Photoluminescence (PL) in Organic Materials

Photoluminescence (PL) in Organic Semiconductor PL emission for organic materials is classified into two common forms, i.e., fluorescence (F) and phosphorescence (P), according to the Jablonski diagram (shown in the image). As shown, S0 represents the singlet electronic GROUND state of the organic materials and S1, S2, ......Sn represents HIGHER discrete singlet electronic states. After light absorption, electrons are excited to HIGHER singlet states (there is a possibility for electrons to reach any higher states, S1, S2,......Sn). These excited electrons at the higher singlet states relax rapidly to S1 state and later fall back to the ground state S0. The transition from the singlet higher states to S1 singlet state accompanied with phonons or thermal energy, namely internal conversion (IC). This phenomenon does not contribute any light emissions, and we will have no PL emission. After relaxation, the transition from S1 to S0 is resulted by photon emissions, called fluorescence (denoted by F in the image). There is also a possibility for electrons to transfer from the S1 to triplet states such as T1,T2, ..., Tn before falling back to S0 called intersystem crossing (ISC) process. Followed by falling of electrons from T2 to T1 along with photon emissions called phosphorescence (denoted by P in the image or this is also sometimes called delayed fluorescence. Moreover, there is also an IC process in the triplet states as shown. For those who are interested to know more about Photoluminescence (PL) spectroscopy. Here is a discussion ! PL spectroscopy is used to study the electronic and optical properties of materials. In this technique, simply photons excite electrons to higher energy levels, and the subsequent relaxation of electrons to the lower energy levels results in the emission of photons (light). The techniques provide information about the band structure of the materials, defects states, and the composition, etc. In PL spectroscopy, there are two phenomena occurring, i.e., radiative and non-radiative recombination. The radiative recombination of charges produces photons, whereas the non-radiative recombination does not produce photons but instead, it generates heat and phonons or thermal energy. In the radiative emission, PL can then be separated into two main types, i.e., fluorescence and phosphorescence. Fluorescence means immediate emission of light, while the phosphorescence means delayed emission, and it is also called delayed fluorescence. Please do like, comment, and share my post. Thank you for your time and attention!