White‐Emissive Self‐Assembled Organic Microcrystals

Abstract

Organic semiconductor micro-/nanocrystals with regular shapes have been demonstrated for many applications, such as organic field-effect transistors, organic waveguide devices, organic solid-state lasers, and therefore are inherently ideal building blocks for the key circuits in the next generation of miniaturized optoelectronics. In the study, blue-emissive organic molecules of 1,4-bis(2-methylstyryl)benzene (o-MSB) can assemble into rectangular microcrystals at a large scale via the room-temperature solution-exchange method. Because of the Förster resonance energy transfer, the energy of the absorbed photons by the host matrix organic molecules of o-MSB can directly transfer to the dopant organic molecules of tetracene or 1,2:8,9-dibenzopentacene (DBP), which then emit visible photons in different colors from blue to green, and to yellow. More impressively, by modulating the doping molar ratios of DBP to o-MSB, bright white-emissive organic microcrystals with well-preserved rectangular morphology can be successfully achieved with a low doping ratio of 1.5%. These self-assembled organic semiconductor microcrystals with multicolor emissions can be the white-light sources for the integrated optical circuits at micro-/nanoscale.

Room‐Temperature Phosphorescence in Pure Organic Materials: Halogen Bonding Switching Effects

“…To reveal the PL mechanism for S‐2CN/I−Ph−NH 2 and S‐2I/I−Ph−NH 2 hgDCs, we further performed theoretical calculations by using the ONIOM (B3LYP/GENECP: UFF) approach to optimize the geometry (see the Supporting Information for details) . In the model, a S‐2CN (S‐2I) molecule is doped in I−Ph−NH 2 cryatals by substitution of five I−Ph−NH 2 molecules without affecting the original crystal structure of I−Ph−NH 2 , which is reasonable as no position shift of characteristic peaks was observed in X‐ray diffraction (XRD) patterns (Figure S6) . The simulated result of S‐2CN/I−Ph−NH 2 hgDCs is shown in Figure a, in which S‐2CN⋅⋅⋅I−Ph−NH 2 halogen bonds between S‐2CN and I−Ph−NH 2 are formed.…”

“…[4c] In the model, a S-2CN (S-2I) molecule is doped in IÀPhÀNH 2 cryatals by substitution of five IÀPhÀNH 2 molecules without affecting the original crystal structure of IÀPhÀNH 2 ,w hich is reasonable as no positions hift of characteristic peaks was observed in X-ray diffraction (XRD) patterns ( Figure S6). [17] The simulated result of S-2CN/IÀPhÀNH 2 hgDCsi ss hown in Figure 3a,i nw hich S-2CN···IÀPhÀNH 2 halogen bonds between S-2CN and IÀPhÀ NH 2 are formed. Thus S-2CN molecule is seriously restricted in the crystalline host with the assistance of halogen bonds and other intermolecular-CN···X (X = H, N) and -CH···I interactions.…”

Tunable Emission Color and Morphology of Organic Microcrystals by a “Cocrystal” Approach

“…In terms of fundamental studies and potential applications, the ability to tune and control the luminescent color of an organic material is important to achieve multicolor displays and to meet the needs of next generation light‐emitting materials . For example, our group recently reports that organic microcrystals with various emission colors can be achieved through a doping approach based on the Förster resonance energy transfer . Additionally, recent advances in organic emissive crystals have indicated that the intermolecular interaction or molecular stacking mode of the aggregate state plays a key role in the luminescent characteristics .…”

Recent Advances in 1D Organic Solid‐State Lasers

“…In contrast, organic molecules are of merits which are complementary with their inorganic counterparts, such as low cost in processing, high photoluminescence (PL) wavelength tunability ranging from ultraviolet to infrared, high PL efficiency, and high flexibility in modifying molecular structures . Moreover, there are abundant excited state processes for most organic materials for which the four‐level system can be easily fulfilled for population inversion .…”