Design Strategy for Robust Organic Semiconductor Laser Dyes

Abstract

A new molecular design for organic semiconductor laser dyes showing excellent optical properties and high robustness is disclosed in this work. The suitability of a furan moiety for increasing the thermal and photostability in newly developed furan-based derivatives (BPBFCz) is demonstrated by comparing a well-known laser molecule (BSBCz) having a bis-stilbene unit. The new derivatives exhibited high photoluminescence quantum yields of nearly 100% and radiative rate constants of ∼10 9 s −1 in both solution and doped films, and their properties were also excellent in neat films. The amplified spontaneous emission (ASE) thresholds of the BPBFCz materials were found to be very low (<1 μJ cm −2 ), and the excited-state absorption in the ASE oscillation region was negligible, which is preferable for laser applications. In addition to these excellent optical properties, which are comparable or superior to those of BSBCz, the decomposition temperatures of the BPBFCz emitters were much higher than that of BSBCz, resulting in the suppression of impurity formation during the thermal deposition. In addition, the photostability of the new materials was dramatically improved compared with that of BSBCz. This study serves as a very significant advancement toward the practical application of organic semiconductor laser diodes and provides molecular design guidelines for robust organic laser molecules.

Organic molecules with inverted gaps between first excited singlet and triplet states and appreciable fluorescence rates

“…Furthermore, it also needs to be investigated whether INVEST emitters could be good candidates for electrically pumped organic lasers. 141,142 The INVEST emitters discovered in this study solve one of the disadvantages of most previous MRE emitters by having inverted singlet-triplet gaps, which will make triplet exciton harvesting even more efficient and improve long-term device stability. Moreover, our INVEST emitter design benefits from all the advantages of MRE emitters.…”

Suppression of external quantum efficiency rolloff in organic light emitting diodes by scavenging triplet excitons

“…1b . Faster nonradiative relaxation of BSBCz triplet excitons was already reported, as the triplet exciton lifetime is in nano-second range 42 , 52 . Advantageously, due to suppressed STA in BSBCz-based devices (devices B, C), efficiency rolloff suppressed until the current density is 500 mA cm −2 , where after the device starts to breakdown due to joule heating under DC operation (Fig.…”

“…Major reason is that triplet scavenging mechanism realized using BSBCz as the host instead of CBP, led to the complete removal of triplets from the emitter molecules, thereby completely avoiding the emitter-emitter STA. The other reasons are negligible overlap of the DCNP emission spectrum with the BSBCz triplet absorption spectrum 42 , while faster triplet relaxation lifetime of BSBCz became an additional advantage 42,52 to complete suppression of emitter-host STA.…”

Realizing Near‐Infrared Laser Dyes through a Shift in Excited‐State Absorption

“…Therefore, the effective σ em (σ em−eff ) is defined by the following equation: σ em−eff = σ em − (σ ABS + σ SS + σ TT ), where σ ABS is the absorption cross section of the ground‐state species, σ SS is the singlet–singlet excited‐state absorption cross section, and σ TT is the triplet–triplet excited‐state absorption cross section. [ 30,31 ] The stimulated emission is inhibited when the σ em spectrum largely overlaps with the absorption spectra. Since the excitation light source was short‐pulse driven, the effect of σ TT seemed to be negligible in this case.…”