Triplet state and phosphorescence of hole-transport layer and its triplet exciton confinement

Synthesis of Soluble Host Materials for Highly Efficient Red Phosphorescent Organic Light-Emitting Diodes

“…28,31,32 The 0-0 transition energy determined from this procedure was assigned as triplet energy (T 1 ). The emission spectra obtained at the various delay time and subtraction spectra which were deconvoluted by some vibrational components are shown in Figure S2 (see Supporting Information).…”

Band Gap Grading of Stacked Cu(In,Ga)S2 Thin Films

“…Thus, the reduced V oc in A + B + A was attributed to the higher density of the defect states, because the film qualities may have been deteriorated by the doubled interface at the front (dense/porous) and back (porous/dense) layers, as well as the small grains of the two (front and back) layers . Furthermore, the bandwidth of photoluminescence in A + B + A was broader than that in B + A (Figures (b)), which supported the higher density of the defect states in A + B + A . In this regard, the reduced film quality led to the low V oc in A + B + A, which resulted in only slight improvement in the efficiency of A + B + A, despite the improved J sc , compared to B + A.…”

“…To examine the temperature dependence of photoluminescence spectra in more detail, the photoluminescence spectra of the dense layer were obtained as a function of temperature. With decreasing temperature, the intensity increased and the bandwidth decreased (Figure (a)), which indicated the suppression of the thermally activated nonradiative decay and the phonon modes at low temperatures, respectively . Moreover, the peak energy changed nonlinearly as a function of the temperature (Figure (b)), which was attributed to the electron–phonon interactions, in addition to the thermal expansion .…”

“…However, the identical front layer (A) in both films led to similar E g and shunt resistance of the solar cells, suggesting that the defect states influenced V oc of solar cells, because a strong temperature dependence was observed in A + B + A. Indeed, the lifetime of the carriers in B + A also exhibited the temperature dependence (Figure (c)), indicating the non‐negligible density of the defect states . Nevertheless, the lifetime of the carriers in A + B + A (Figure (d)) was even shorter than that in B + A, which implied that the density of the defect states increased, leading to nonradiative decay in A + B + A.…”

Singlet Exciton Diffusion in Vacuum‐Evaporated Films of Amine‐Based Materials as Studied by Photocurrent and Photoluminescence Quenching Methods

“…Note, however, that to calculate the values of relevant diffusion coefficient, the intrinsic lifetime of excitons is needed. As results from the time‐of‐fluorescence‐decay measurements, for singlet excitons in vacuum‐evaporated films of 2TNATA, m‐MTDATA, and in TPD, . Taking these values into account, we have estimated the corresponding values of singlet diffusion coefficient varying between D S ≈ 1 × 10 −3 and D S ≈ 1 × 10 −2 cm 2 s −1 .…”