Modelling quenching mechanisms of disordered molecular systems in presence of molecular aggregates

The exciton density dynamics recorded in time-resolved spectroscopic measurements is a useful tool to recover information on energy transfer (ET) processes that can occur at different timescales, up to the...

A Universal Thermally Activated Delayed Fluorescence Host with Short Triplet Lifetime for Highly Efficient Phosphorescent OLEDs with Extremely Low Efficiency Roll-off

Triplet-involved quenching processes lead to significant efficiency roll-off in phosphorescent organic light-emitting diodes (OLEDs). Thermally activated delayed fluorescence (TADF) materials can reduce the triplet exciton density in the emitting layer...

Transient Analysis of Poly (3,4-Ethylenedioxythiophene) Poly (Styrenesulphonate) (PEDOT: PSS)- Polyfluorene Organic Polymer Layer Light Emitting Diode

In this paper, we have simulated a bi-organic polymer multilayered Light Emitting Diode (LED). It presents the transient analysis of the OLED device. Poly (9, 9-dioctylfluorene) (PFO) is used as an interlayer between Hole Transport Layer (HTL) and Lithium fluoride (LiF) which is responsible for enhancing the electron injection in the device. Hence, it is called as Electron Injection Layer (EIL). PFO acts as a photo catalyst, which improves the device performance. Silvaco TCAD is used for the extraction of electro-optical characteristics. It is done using 1 and 2-dimentional simulation process. Solution of differential equations is derived from Langevin recombination model. Transient response analysis and comparison is done for exciton density and anode current for different thickness of PFO layer. It is found that transient response with respect to anode current and exciton density is better when a Poly (9, 9-dioctylfluorene) (PFO) layer is inserted between anode and Hole Injection Layer (HIL). The analysis and comparison is done for 65 nm, 120 nm and 240 nm thick layers and it is observed that transient response is best at 65 nm layer thicknesses for both exciton density and anode current. Also, J-V characteristics has been found for the structure where current density is 1.8 A/ .m2 which is remarkably high as compared to the devices discussed in prose. The results agree well with that available in literature. Poly (3,4-ethylenedioxythiophene) poly (styrenesulphonate) (PEDOT:PSS) results in low operating voltage of the device which is 4V here.

Synthesis, crystal structure, and photophysical properties of 2,9-disubstituted peropyrene derivatives

Peropyrene is a promising candidate molecule for use in organic solar cells based on singlet fission, because it fulfills the energy matching requirement for singlet fission. We prepare three 2,9-disubstitued peropyrene derivatives and investigate their crystal structures, photophysical properties, and singlet fission phenomenon. Although each derivative shows different molecular overlap motifs in solid state, no singlet fission occurs under normal exciton density conditions due to the substantial stabilization of the first excited singlet (S1) state. In contrast, under high exciton density conditions, singlet fission from highly excited singlet (Sn) states, which is generated by singlet–singlet exciton annihilation, takes place to produce a triplet exciton. We also investigate the reverse process of singlet fission, that is, triplet–triplet annihilation, of peropyrene in solution state to explore the possibility of photon upconversion.