In recent years, there has been a growing interest in purely organic materials showing ultralong room‐temperature phosphorescence with lifetimes in the range of seconds. Still, the longest known phosphorescence lifetimes are only achieved with crystalline systems so far. Here, a rational design of a completely new family of halogen‐free organic luminescent derivatives in amorphous matrices, displaying both conventional fluorescence and phosphorescence is reported. Hydrogen bonding between the newly developed emitters and an ethylene‐vinyl alcohol copolymer (Exceval) matrix, which efficiently suppresses vibrational dissipation, enables bright long‐lived phosphorescence with lifetimes up to 2.6 s at around 480 nm. The importance of the chosen matrix is shown as well as the implementation in an organic programmable luminescent tag.

Biluminescent organic emitters show simultaneous fluorescence and phosphorescence at room temperature. So far, the optimization of the room-temperature phosphorescence in these materials has drawn the attention of research. However, the continuous-wave operation of these emitters will consequently turn them into systems with vastly imbalanced singlet and triplet populations, which is due to the respective excited-state lifetimes. This study reports on the exciton dynamics of the biluminophore NPB (N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1-biphenyl)-4,4-diamine). In the extreme case, the singlet and triplet exciton lifetimes stretch from 3 ns to 300 ms, respectively. Through sample engineering and oxygen quenching experiments, the triplet exciton density can be controlled over several orders of magnitude, allowing us to study exciton interactions between singlet and triplet manifolds. The results show that singlet–triplet annihilation reduces the overall biluminescence efficiency already at moderate excitation levels. Additionally, the presented system represents an illustrative role model to study excitonic effects in organic materials.

Most materials recently developed for room temperature phosphorescence (RTP) lack in practical relevance due to their inconvenient crystalline morphology. Using amorphous material systems instead, programmable luminescent tags (PLTs) based on organic biluminescent emitter molecules with easy processing and smooth sample shapes are presented recently. Here, the effective quenching of the emitter's RTP by molecular oxygen (O 2 ) and the consumption of the excited singlet O 2 through a chemical reaction represent the central features. With customized activation schemes, high-resolution content can be written and later erased multiple times into such films, providing a versatile yet simple photonic platform for information storage. However, two important limitations remain: The immutable fluorescence of the emitters outshines the phosphorescent patterns by roughly one order of magnitude, allowing readout of the PLTs only after the excitation source is turned off. The programming of these systems is a rather slow process, where lowest reported activation times are still >8 s. Here, a material-focused approach to PLTs with fast activation times of 120 ± 20 ms and high-contrast under continuous-wave illumination is demonstrated, leading to accelerated programming on industry relevant time scales and a simplified readout process both by eye and low cost cameras.

Conventional organic optoelectronic devices suffer from low carrier mobility limited by the static and dynamic disorder. Organic crystals with long-range order can circumvent the effects of disorder and significantly improve the charge transport. While highly ordered organic crystals offer the desirable electronic coupling strength and charge transport, their integration into largearea optoelectronic devices remains a challenge. Here, monolithic integrated triclinic crystal rubrene light-emitting diodes (LEDs) are presented using epitaxial growth with functional additives being engineered into the films. Superior charge transport, excellent operational and long-term stability in these light-emitting devices are demonstrated. By comparing two rubrenebased LEDs, one made from amorphous and one from crystalline rubrene layers, their exciton dynamics are estimated using comprehensive transient electroluminescence simulation. The crystalline LEDs show high triplet-triplet annihilation (TTA) rate constant similar to TTA rate constant of triclinic single crystals determined by optical spectroscopy. At the same time, the crystalline phase enhances drastically the singlet-fission and bimolecular annihilation rates, which reduces the overall performance of the LED compared to its amorphous counterpart. Finally, an outlook on the potential applications of rubrene and/or its derivatives crystalline films are provided for enhancing the performance of organic and hybrid optoelectronic devices.

for various fields of application, such as chemical material analysis, characterization of light sources, or calibration of monochromators and laser sources. Established techniques for realizing wavelength-selective light detection use one of two primary approaches: first, wavelength separation by an auxiliary structure, [1] i.e., a filter array or grating, where narrow light bands are directed onto individual pixels of a photodetector (PD) (array) with a broadband response; second, wavelength separation by the photoactive part itself, achieved by a multilayer arrangement of detectors, where every single detector is sensitive to a specific wavelength band. [2,3] Such spectroscopic devices commonly comprise solid hardware components that restrict them from versatile integration.Recent developments, however, demonstrate both the huge drive and great potential in terms of easy-to-integrate, low-cost, or lightweight applications, [4] e.g., narrowband photodiodes, [5][6][7] voltage-tunable Fabry-Pérot micro-interferometers, [8] or broadband sensors requiring wavelength multiplexing. [9] A smart approach to significantly reduce the device complexity was presented by Gautam et al. [10] A single-pixel and single-layer device was used to achieve a wavelength-sensitive photocurrent response that can discriminate red, green, and blue (RGB) values via the polarization of a polymer film in an aqueous surrounding. Only recently, a system was presented that consists of a multilayer single pixel of graded-bandgap perovskites evoking a wavelength-sensitive photocurrent response. [11] Here, we present a single-chip wavelength sensor that exploits the dynamics of singlet and triplet states to discriminate a certain input signal. We employ a solution-processed host-guest system comprising organic room-temperature phosphors and fluorescent colloidal quantum dots (QDs), thereby introducing a new, promising application for organic room-temperature phosphorescence (RTP). The latter has been put to multifaceted use, [12] such as programmable luminescent tags, [13] oxygen sensing, [14] or moisture sensing. [15] Owing to their unique scalable optical properties, high quantum yield, and elevated photostability, colloidal quantum dots proved themselves valuable in a myriad of applications, like light-emitting diodes (LEDs), [16,17] solar cells, [18][19][20] or transistors. [21,22] Here, we present a single-layer approach that turns wavelength information into a distinct photocurrent response with a spectral resolution down to 1 nm and below while covering a wavelength range from 300 to 410 nm.Wavelength-discriminating systems typically consist of heavy benchtop-based instruments, comprising diffractive optics, moving parts, and adjacent detectors. For simple wavelength measurements, such as lab-on-chip light source calibration or laser wavelength tracking, which do not require polychromatic analysis and cannot handle bulky spectroscopy instruments, lightweight, easyto-process, and flexible single-pixel devices are attracting increasing atten...