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Large graphene-like molecules with four zigzag edges are ideal gain medium materials for organic near-infrared (NIR) lasers. However, synthesizing them becomes increasingly challenging as the molecular size increases. In this study, we introduce a new intramolecular radical-radical coupling approach and successfully synthesize two fused triangulene dimers (1a/1b) efficiently. X-ray crystallographic analysis of 1a indicates that there is no intermolecular π-π stacking in the solid state. When the more soluble derivative 1b is dispersed in polystyrene thin films, amplified spontaneous emission in the NIR region is observed. Using 1b as the active gain material, we fabricate solution-processed distributed feedback lasers that exhibit a narrow emission linewidth at around 790 nm. The laser devices also exhibit low thresholds with high photostability. Our study provides a new synthetic strategy for extended nanographenes, which have diverse applications in electronics and photonics. J.W. acknowledges financial support from the NRF Investigatorship Award (NRF-NRFI05-2019-0005), the A*STAR AME grant (A20E5c0089) and start-up grant from the Joint School of National University of Singapore and Tianjin University@Fuzhou. The group at the University of Alicante thanks financial support from the “Ministerio de Ciencia e Innovación” (MCIN) of Spain and the European Regional Development Fund (grant No. PID2020-119124RB-I00) and from the Generalitat Valenciana though grant No. AICO/2021/093. Besides, this study part of the Advanced Materials program supported by the Spanish MCIN with funding from European Union NextGenerationEU and by Generalitat Valenciana (grant no. MFA/2022/045). Z.S. is grateful to the financial support from National Natural Science Foundation of China (Grant No. 21971187, 22222110), Natural Science Foundation of Tianjin (19JCJQJC62700) and the Haihe Laboratory of Sustainable Chemical Transformations.

Donor–Acceptor (D–A) naphthalimides (NI) are highly fluorescent multitask compounds that have demonstrated success in a variety of optoelectronic applications, among which, thin film organic lasers (TFOLs) are not included. Here we assess the potential of various NI derivatives for lasing applications by investigating their amplified spontaneous emission (ASE) properties when dispersed in polystyrene thin films. To overcome the relatively low ASE photostability measured in the NIs, a series of peryleneimides (PI) derivatives, with similar chemical structure but with more extended π-conjugation, is synthesized and reported here, together with a complete characterization of their optical and ASE properties, both in solution and thin film. Most investigated compounds show ASE, with emissions at different wavelengths spanning from the blue to the red, depending on the derivative. Furthermore, surface emitting TFOLs with top-layer polymeric distributed feedback resonators are fabricated and characterized. This work represents an advance in the field of low-cost TFOLs, by including two families of successful laser dyes, NIs and PIs, the latter with significantly better photostability. The group at the University of Alicante acknowledges financial support from the “Ministerio de Ciencia e Innovación/Agencia Estatal de investigación” (MCIN/AEI) of Spain, European Regional Development Fund and European Social Funds (project PID2020-106114GB-I00) and from the Conselleria de Innovación, Universidades y Sociedad Digital de la Comunidad Valenciana (Grant No. AICO/2021/093). The team of the University of Castilla la Mancha acknowledges financial support from the MCIN/AEI of Spain (project PID2020-119636GB-I00 and RED2018-102331-T) and by FEDER Una manera de hacer Europa and Junta de Comunidades de Castilla-La Mancha (JCCM-FEDER) (SBPLY/17/180501/000189 and SBPLY/17/180501/000114). B. Donoso is grateful for a FPU predoctoral contract (FPU16/05099). I. Torres-Moya thanks to the Junta de Comunidades de Castilla-La Mancha for a post-doctoral contract (SBPLY/19/180501/000346). Finally, we acknowledge the computer resources, technical assistance, and expertise provided by the High Performance Computing Service of UCLM.

Perylenediimide (PDI) compounds with no substituents in their core are widely used as the active units of thin-film organic lasers. Recently, bay-substituted PDIs (b-PDIs) bearing two sterically hindering diphenylphenoxy groups at the 1,7-bay positions have received great attention because they show red-shifted emission with respect to bay-unsubstituted PDIs, while maintaining high photoluminescence (PL) quantum yields and low amplified spontaneous emission (ASE) thresholds even at high doping rates. However, their ASE photostability is relatively low compared to that of state-of-the-art PDIs. Thus, the design of b-PDIs with improved ASE photostability remains a challenge. Here, the synthesis of two b-PDIs with phenyl-type substituents at the imide positions is reported. Complete characterization of their optical properties, including absorption, PL, ASE, and transient spectroscopy, supported also by quantum chemical calculations, is performed with the dyes diluted in either a liquid solvent or a polystyrene film. Film experiments were accomplished at very low doping rates, to resemble the isolated molecule behavior, and also in a range of increasing doping rates, to investigate concentration quenching effects. The reported b-PDIs show improved ASE photostability (3-fold) with respect to b-PDIs with aliphatic-type substituents at the imide positions, whilst they show more propensity toward aggregation. The authors thank the Spanish Ministry of Economy and Competitiveness MINECO and the European Social Funds (project MAT2015-66586-R and FPI fellowship BES-2016-077681), the Ministry of Science and Innovation (MICINN) and the European FEDER funds (CTQ2016-77039-R, PGC2018-099568-B-I00, and PID2019-109200GB-I00, and Unidad de Excelencia María de Maeztu CEX2019-000919-M), and the Generalitat Valenciana (PROMETEO/2020/077 and SEJI/2018/035). J.A. acknowledges the MICINN for the “Ramón-y-Cajal” Fellowship (RyC-2017-23500).

Perylene‐fused, aggregation‐free polycyclic aromatic hydrocarbons with partial zigzag periphery (ZY‐01, ZY‐02, and ZY‐03) were synthesized. X‐ray crystallographic analysis reveals that there is no intermolecular π–π stacking in any of the three molecules, and as a result, they show moderate‐to‐high photoluminescence quantum yield in both solution and in the solid state. They also display the characteristic absorption and emission spectra of perylene dyes. ZY‐01 and ZY‐02 with a nearly planar π‐conjugated skeleton exhibit amplified spontaneous emission (ASE) when dispersed in polystyrene thin films. Solution‐processed distributed feedback lasers have been fabricated using ZY‐01 and ZY‐02 as active gain materials, both showing narrow emission linewidth (

Zigzag edged nanographenes such as peri-acenoacenes are promising materials for organic lasers, but the effects of heteroatom doping on the electronic properties and gain medium performance remain unclear. Herein, the facile synthesis of a new 1,2-oxaborine (BO) doped peri-tetracenotetracene derivative, the bis(1,2-oxaborine)peri-tetracenotetracene (BOTT-Mes), is reported. X-ray crystallographic analysis confirms the BO-doped planar structure and the nonexistence of intermolecular π–π stacking in solid state. Compared with the all-carbon peri-tetracenotetracene derivative (TT-Ar), the BO-doped BOTT-Mes exhibits more disrupted π-conjugation at the BO sites, a lower-lying highest occupied molecular orbital, and a larger energy gap. Due to its rigid skeleton and nonaggregative feature, it displays well-resolved absorption and emission spectra with a small Stokes shift (8 nm) and high photoluminescence quantum yield (80%) when it is dispersed in a polystyrene (PS) thin film. Notably, 1,2-oxaborine doping improves the film amplified spontaneous emission (ASE) performance, with a lower ASE threshold (Eth-ASE = 66 µJ cm–2) as compared to the TT-Ar doped PS film (Eth-ASE = 100 µJ cm–2). Furthermore, a low threshold (22 µJ cm–2) solution-processed distributed feedback laser is fabricated, indicating the feasibility of using BOTT-Mes as gain medium for practical laser applications. J.W. acknowledges financial support from A*STAR Advanced Manufacturing and Engineering grant (A20E5c0089) and National Research Foundation Investigatorship Award (NRF-NRFI05-2019-0005). The group at the University of Alicante acknowledges financial support from the “Ministerio de Ciencia e Innovación” of Spain, European Regional Development Fund and European Social Funds (PID2019-106114GB-I00 and BES-2016-077681) and from the Conselleria de Innovación, Universidades y Sociedad Digital de la Comunidad Valenciana (Grant No. AICO/2021/093).

We report the synthesis of a dibenzodinaphthocoronene (DBDNC) derivative as a novel nanographene with armchair, zigzag, and fjord edges, which was characterized by NMR and X-ray crystallography as well as infrared (IR) and Raman spectroscopies. Ultrafast transient absorption (TA) spectroscopy revealed the presence of stimulated emission signals at 655 nm and 710 nm with a relatively long lifetime, which resulted in dual amplified spontaneous emission (ASE) bands under ns-pulsed excitation, indicating the promise of DBNDC as a near-infrared (NIR) fluorophore for photonics. Our results provide new insight into the design of nanographene with intriguing optical properties by incorporating fjord edges. This work was financially supported by the Okinawa Institute of Science and Technology Graduate University (OIST), the Max Planck Society, JSPS KAKENHI Grant No. JP19K24686, and the European Union’s Horizon 2020 Research and Innovation program under grant agreement no. 101017821 (LIGHT-CAP). G. M. P thanks Fondazione Cariplo (Grant no. 2018-0979) for financial support. Researchers from the University of Alicante acknowledge support from the Spanish Ministerio de Ciencia e Innovación and the European Union (Next Generation EU) through grant no. PID2020-119124RB-I00; and to the Conselleria de Innovación, Universidades y Sociedad Digital de la Comunidad Valenciana (Grant No. AICO/2021/093).

A naphtho[2,1-b:6,5-b′]difuran derivative was found to serve as an effective violet-emitting laser dye. It showed amplified spontaneous emission at 413 nm with the threshold of 1.1–2.9 mJ cm−2 using 0.1–0.5 wt% in polystyrene film. Lasing was also demonstrated using all-polymeric distributed-feedback lasers emitting at 411–417 nm with the threshold of 2.0–2.9 mJ cm−2. This work was supported by JSPS KAKENHI grant JP19H05716 (to H. T.) and by the “Ministerio de Ciencia, Innovación y Universidades” of Spain, via grants MAT2015-66586-R and PID2020-119124RB-I00 and by the “Generalitat Valenciana” through grant AICO/2021/093.

The molecule N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine (TPD) has been widely used in optoelectronic applications, mainly for its hole-transporting properties, but also for its capability to emit blue light and amplified spontaneous emission, which is important for the development of organic lasers. Here, we report deep-blue-emitting distributed feedback (DFB) lasers based on TPD dispersed in polystyrene (PS), as active media, and dichromated gelatin layers with holographically engraved relief gratings, as laser resonators. The effect of the device architecture (with the resonator located below or on top of the active layer) is investigated with a dye (TPD) that can be doped into PS at higher rates (up to 60 wt%), than with previously used dyes (&lt, 5 wt%). This has enabled changing the index contrast between film and resonator, which has an important effect on the laser performance. With regards to thresholds, both architectures behave similarly for TPD concentrations above 20 wt%, while for lower concentrations, top-layer resonator devices show lower values (around half). Remarkably, the operational durability of top-layer resonator devices is larger (in a factor of around 2), independently of the TPD concentration. This is a consequence of the protection offered by the resonator against dye photo-oxidation when the device is illuminated with pulsed UV light.

High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry. Spanish Ministry of Economy and Competitivity (MINECO) and European Community (FEDER) through grant no. MAT2015-66586-R.

The search of compounds emitting in the near-infrared (NIR) has been accelerated owing to their use in biomedical and telecommunications applications. In this regard, nanographenes (NGs) are attractive materials adequate for integration with other technologies, which have recently demonstrated amplified spontaneous emission (ASE) and lasing across the visible spectrum. Here, the optical and ASE properties of four-zigzag edged NGs of the [m,n]peri-acenoacene family are reported, whose size is increased through conjugation extension by varying n (from 3 to 5) while keeping m = 2. Results show that such 1D conjugation extension method is more efficient in terms of shifting the photoluminescence (PL) to the infrared (PL at 710 nm in the larger compound, PP-Ar) than through 2D conjugation extension as in previously reported NGs (PL at 676 nm with the largest compound FZ3, with n = 3 and m = 4). Additionally, PP-Ar shows dual-ASE (at 726 and 787 nm), whose origin is elucidated through Raman and transient absorption spectroscopies. These compounds’ potential for red and NIR lasing is demonstrated through the fabrication of distributed feedback lasers with top-layer resonators. This study paves the way towards the development of stable low-cost all-plastic NIR lasers. The authors acknowledge financial support from the “Ministerio de Ciencia, Innovación y Universidades” of Spain, European Regional Development Fund and European Social Funds (MAT2015-66586-R, PDI2019-106114GB-I00, BES-2016-077681, PGC2018-098533-B-100 and RED2018-102815-T). J.C. thanks the Junta de Andalucía of Spain (UMA18FEDERJA057). The authors also thank the Research Central Services (SCAI) of the University of Málaga. F.G. acknowledges the Spanish Government for an FPI grant. G.M.P. thanks Fondazione Cariplo (grant no 2018-0979) for the financial support. J.W. acknowledges the “Agency for Science, Technology and Research of Singapore” for financial support from A*STAR AME grant (A20E5c0089). A.M.R. and F.S. have received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. [816313]).

The spectral overlap between stimulated emission (SE) and absorption from dark states (i.e. charges and triplets) especially in the near-infrared (NIR), represents one of the most effective gain loss channel in organic semiconductors. Recently, bottom-up synthesis of atomically precise graphene nanostructures, or nanographenes (NGs), has opened a new route for the development of environmentally and chemically stable materials with optical gain properties. However, also in this case, the interplay between gain and absorption losses has hindered the attainment of efficient lasing action in the NIR. Here, we demonstrate that the introduction of two fluoranthene imide groups to the NG core leads to a more red-shifted emission than the precursor NG molecule (685 vs. 615 nm) and also with a larger Stokes (45 nm vs. 2 nm, 1026 cm-1 vs. 53 cm-1, respectively). Photophysical results indicate that, besides the minimisation of ground state absorption losses, such substitution permits to suppress the detrimental excited state absorption in the NIR, which likely arises from a dark state with charge-transfer character. This has enabled NIR lasing (720 nm) from all-solution processed distributed feedback devices with one order of magnitude lower thresholds than those of previously reported NIR-emitting NGs. This study represents an advance in the field of NGs and, in general, organic semiconductors photonics, towards the development of cheap and stable NIR lasers. G.M.P. thanks Fondazione Cariplo for financial support (grant n° 2018-0979). R.M.M., P.G.B., J.M.V., J.A.Q. and M.A.D.G. acknowledge funding from the Spanish Ministry of Economy and Competitiveness (MINECO), the European Regional Development Fund (FEDER) and European Social Funds (ESF; grant n° MAT2015-66586-R and FPI fellowship BES-2016-077681). Q.C., K.M. and A.N. are grateful for the financial support by the Max Planck Society and the ANR-DFG NLE Grant GRANAO by DFG 431450789. K.M. acknowledges a fellowship from Gutenberg Research College, Johannes Gutenberg University Mainz. R.K. and A.N. appreciate the support by the Okinawa Institute of Science and Technology Graduate University. Y.I. and A.N acknowledge financial support from the Japan Society of Promotion Science Program for Advancing Strategic International Networks to Accelerate the Circulation of Talented Researchers.

All‐solution processed surface‐emitting organic distributed feedback lasers are attractive devices for low‐cost applications. Here, lasers emitting in the spectral region between 375 and 475 nm, in which both active material and resonator (1D relief gratings) are based on solution‐processable polymer films, are reported. Ten different organic compounds dispersed in polystyrene are used as active layers of the prepared devices. They include various carbon‐bridged oligo(p‐phenylenevinylene) (COPVn, with n = 1,2) derivatives and two terfluorene compounds. The synthesis and complete optical and amplified spontaneous emission properties of one of the COPV1 compounds, COPV1(Me)‐t‐Bu, designed for deep‐blue emission, are also included. The feasibility of the resonator fabrication, performed by holographic lithography with a dichromated gelatine photoresist over the active film, is successfully demonstrated for all devices. Remarkably, no resolution limitations are found even for the lowest grating period (235 nm) required for the fabrication of the laser based on COPV1(Me)‐t‐Bu. It is also demonstrated that the rectangular grating profile with duty cycle 0.75:0.25 (hill:valley) is very convenient to optimize the resonator efficacy. The Spanish team acknowledges support from the Spanish Government (MINECO) and the European Community (FEDER) through Grant No. MAT2015-66586-R. H.T. and E.N. thank the financial support from MEXT (JP19H05716 for H.T. and JP19H0549 for E.N.).

Carbon-bridged oligo(p-phenylenevinylene)s (COPVn with repeating unit n = 1–6) have demonstrated great success as laser dyes for thin-film organic lasers. The excellent photostability observed in the longer homologues is, however, not present in the blue-emitting shorter compounds COPV1 and COPV2, attributed to the unprotected terminal positions that can degrade by photoreaction in the excited state. Here we report the synthesis of various COPV1 and COPV2 derivatives functionalized at the terminal positions with two types of sterically bulky protecting substituents: Tip (2,4,6-triisopropylphenyl) and tert-butyl (t-Bu) groups. Such molecular designs aim at preventing such photodegradation processes and thus to improve their stability. The efficacy of kinetic isotope effect for stabilization is also examined for COPV2, by the addition at terminal positions of deuterium atoms. Absorption, photoluminescence (PL), including PL quantum yield, and amplified spontaneous emission (ASE) studies have been conducted in polystyrene films doped with each of the derivatives. Significant and slight improvements of the ASE photostability are observed for the compounds with Tip groups and deuterium, respectively. Installation of substituents slightly affects the ASE wavelength within the blue spectral region, that is 385–413 nm and 462–474 nm, for COPV1 and COPV2, respectively. Financial support from Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grant MAT2015-66586-R is gratefully acknowledged. This work was partially supported by MEXT and JSPS KAKENHI Grant Numbers JP16H04106 and JP19H05716 to HT and JP19H0549 to EN.

Chemically synthesized zigzag-edged nanographenes (NG) have recently demonstrated great success as the active laser units in solution-processed organic distributed feedback (DFB) lasers. Here, we report the first observation of dual amplified spontaneous emission (ASE) from a large-size NG derivative (with 12 benzenoid rings) dispersed in a polystyrene film. ASE is observed simultaneously at the 685 and 739 nm wavelengths, which correspond to different transitions of the photoluminescence spectrum. Ultrafast pump-probe spectroscopy has been used to ascertain the underlying photophysical processes taking place in the films. DFB lasers, based on these materials and top-layer nanostructured polymeric resonators (i.e., one or two-dimensional surface relief gratings), have been fabricated and characterized. Lasers emitting close to either one of the two possible ASE wavelengths, or simultaneously at both of them, have been prepared by proper selection of the resonator parameters. The Alicante team was funded by Spanish Government (MINECO) and European Community (FEDER), grant number MAT2015-66586-R. The researcher R.M-M was funded by a MINECO FPI fellowship (No. BES-2016-077681). The Singapore team was funded by the NRF Investigatorship programme (NRF-NRFI05-2019-0005). The Milan team has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 816313). G.M.P. acknowledges funding from Fondazione Cariplo, grant No. 2018-0979. C.D. and S.S. acknowledge funding from ERC Starting Grant SOLENALGAE (No. 679814).

10 pags., 7 figs., The increasing number of solution-processed laser compounds that can be implemented as low-cost, flexible, and/or integrated devices, makes necessary the development of reliable methods to delineate all their amplifying signatures and thus to open the door to appropriate cross-sample comparisons. Seeking to solve this problem, a new formalism to retrieve the losses and the optical gains from Amplified Spontaneous Emission (ASE) spectra as a function of the excitation density has been recently reported. In this manuscript, we explore the potential of this methodology to unveil relevant information on the photonic properties of the waveguiding devices and on the photophysics of the active materials. We demonstrate that the Variable Pump Intensity method opens the door to understand the relationship between the ASE thresholds and the optical gains and losses, it enables the extraction of the scattering/modal losses of the passive devices, and it can unveil the presence of leaky-modes and excited state absorption. In contrast, it does not perform too well in samples with multiple active species in its current implementation. We have substantiated all these findings using organic semiconductor thin films, several dye-doped polymer thin films and solutions of boron hydride., The researchers from the University of Alicante and LC acknowledge financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grant numbers MAT2015-66586-R and MAT2017-83856-C3-1, respectively.

Surface-emitting distributed feedback (DFB) lasers with both, resonator and active material based on solution-processable polymers, are attractive light sources for a variety of low-cost applications. Besides, the lasers should have competitive characteristics compared to devices based on high-quality inorganic resonators. Here, we report high performing all-solution-processed organic DFB lasers, consisting of water-processed photoresist layers with surface relief gratings located over the active films, whose emission properties can be finely tuned through resonator design. Their laser threshold and efficiency are simultaneously optimized by proper selection of residual resist thickness and grating depth, d. Lowest thresholds and largest efficiencies are obtained when there is no residual layer, while a trade-off between threshold and efficiency is found in relation to d, because both parameters decrease with decreasing d. This behaviour is successfully explained in terms of an overlap factor r, defined to quantify the interaction strength between the grating and the light emitted by the active film and traveling along it, via the evanescent field. It is found that optimal grating depths are in the range 100–130 nm (r ~ 0.5−0.4). Overall, this study provides comprehensive design rules towards an accurate control of the emission properties of the reported lasers.

The design, synthesis and evaluation of the amplified spontaneous emission (ASE) properties of a series of arylalkynyl-benzo[c][1,2,5]thiadiazole (BTD) and [1,2,5]thiadiazolo[3,4-g]quinoxaline (TDQ) derivatives are described. The synthetic strategy entailed the use of Sonogashira and Stille reactions based on the different aromatic natures of the two cores. The ASE properties were measured in thin polystyrene (PS) films doped with different concentrations of the synthesised compounds. BTD derivatives showed narrowing of the photoluminescence spectra (PL), thus revealing their potential laser applications. Only one TDQ derivative showed ASE. X-ray diffraction analysis was carried out to understand the observed results and to establish structure–property relationships. Molecules that showed strong molecular packing quenched the PL emission, thus giving rise to higher ASE thresholds. This is the first study in which ASE has been studied in BTD and TDQ derivatives and it represents a step forward in understanding this class of compounds for laser applications. The Alicante team acknowledges support from Ministerio de Ciencia, Innovación y Universidades, Spain, under projects MAT2015-66586-R (MINECO/FEDER), FIS2017-82919-R (MINECO/AEI/FEDER,UE) and FIS2015-66570-P (MINECO/FEDER). The authors acknowledge financial support from the Junta de Comunidades de Castilla-La Mancha (JCCM-FEDER) (project SBPLY/17/180501/000189), the Spanish Ministry of Economy and Competitiveness (CTQ2013-45415P) and Gobierno Vasco-Eusko Jaularitza (IT-673-13). R. Martı´n is grateful to the MEC for an FPU studentship.

Carbon-bridged bis(aminoaryl) oligo(para-phenylenevinylene)s have been prepared and their optical, electrochemical, and structural properties analyzed. Their radical cations are class III and class II mixed-valence systems, depending on the molecular size, and they show electronic couplings which are among the largest for the self-exchange reaction of purely organic molecules. In their dication states, the antiferromagnetic coupling is progressively tuned with size from quinoidal closed-shell to open-shell biradicals. The data prove that the electronic coupling in the radical cations and the singlet–triplet gap in the dications show similar small attenuation factors, thus allowing charge/spin transfer over rather large distances. ·, We thank MINECO of the Spanish Government (CTQ2015- 69391-P, CTQ2013-40480-R and MAT2015-66856-R) for their support. We also thank the Research Central Services (SCAI) of the University of M#laga. This work is partially supported by Grant-in-Aid for Scientific Research (16H04106 to HTand 15H05754 to EN) and the Strategic Promotion of Innovative Research, JST (to EN) from MEXT, Japan. M.H. and C.L. are grateful to the Deutsche Forschungsgemeinschaft for supporting this work (GRK 2112).

The chemical synthesis of nanographene molecules constitutes the bottom-up approach toward graphene, simultaneously providing rational chemical design, structure-property control and exploitation of their semiconducting and luminescence properties. Here, we report nanographene-based lasers from three zigzag-edged polycyclic aromatics. The devices consist of a passive polymer film hosting the nanographenes and a top-layer polymeric distributed feedback resonator. Both the active material and the laser resonator are processed from solution, key for the purpose of obtaining low-cost devices with mechanical flexibility. The prepared lasers show narrow linewidth (, Chemically synthesized graphene nanosheets offer device design flexibility and improved optoelectronic performance. Here, the authors report solution-processed distributed feedback lasers with graphene nanosheets as active media having linewidths

Perylenediimide (PDI) dyes dispersed in polymer films have demonstrated great success as active materials in thin-film organic lasers (TFOLs). The type of matrix used to host the dye and the dye doping rate are both crucial parameters to optimize laser performance. This work reports the study of two soluble PDIs, the comercial derivative perylene orange (PDI-O) emitting at around 580 nm, and a new dye (b-PDI-A) with substituents at the 1,7 bay positions of the PDI core emitting at around 620 nm, dispersed at different doping levels (up to 8 and 50 wt %, for PDI-O and b-PDI-A, respectively) in two widely used polymers for optoelectronics, polystyrene (PS) and poly(methyl methacrylate) (PMMA). The main goal is to determine which of these two polymers, and at which dye concentration, provides the best results for their use in TFOLs. The assessment of the active materials has been carried out through the analysis of their absorption, photoluminescence, and amplified spontaneous emission (ASE) properties. Their capability to form high-quality optical waveguides has also been studied by determining gain coefficients and waveguide losses. Results have shown that for both types of PDI derivatives PS is better than PMMA at any concentration, which means larger photoluminescence efficiency, lower ASE thresholds, longer ASE operational lifetimes, larger gain, and lower propagation waveguide losses. In addition, the onset concentration at which dye aggregation becomes significant as to negatively affect the optical properties is lower in PMMA than in PS; thus, the larger the blending ratio, the larger the superiority of PS with respect to PMMA is. Financial support from Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grants MAT2015-66586-R and CTQ2016-77039-R (AEI/FEDER, UE) is gratefully acknowledged. R.M-M is supported by a MINECO FPI contract (no. BES-2016-077681). M.A.D-G acknowledges support from the University of Alicante and to the Spanish Ministry of Education (grant no. PR2015-00390) to perform a sabbatical stay at UCSB.

Thin-film organic lasers are attractive light sources for a variety of applications. Recently, it is reported that carbon-bridged oligo(p-phenylenevinylene)s (COPVn with repeating unit n = 1–6) function as unique laser dyes which combine high fluorescence efficiency, wavelength tunability, and both thermal and photostability, making them ideal for use in organic semiconductor lasers. However, in order to obtain such excellent properties, COPVn require blending in a matrix, such as a thermoplastic polymer, thus leading to miscibility issues, limited absorption, and charge transporting properties. Here, high-performance lasers with a novel active polymer poly-COPV1, based on the basic unit of COPV1 and prepared as a high-quality neat film, are reported which overcome the trade-off between the device performance and durability. The prepared lasers show thresholds 30 times lower and operational lifetimes 300 times longer than devices based on COPV1 dispersed in polystyrene. The low threshold operation allows the poly-COPV1 lasers to be pumped by a nitride diode laser., Spanish Government (MINECO). Grant Numbers: MAT2011-28167-C02-01, MAT2015-66586-R European Community (FEDER) MINECO FPI Fellowship. Grant Number: BES-2009-020747 Junta de Castilla y León (JCYL) Postdoctoral Fellowship. Grant Number: SA046U16 MEXT. Grant Numbers: 16H04106, 15H05754 Engineering and Physical Sciences Research Council. Grant Numbers: EP/K503162/1, EP/J009016/1 Royal Society Wolfson Research

Latest advances from our research group towards improving the performance of solution-processed distributed feedback lasers will be discussed. They include advances on the laser material and the resonator and their application as optical sensors.

Two-dimensional (2D) distributed feedback (DFB) lasers with gratings imprinted by thermal nanoimprint lithography on the active film are reported. They show thresholds for lasing of ∼10 kW/cm2, similar to the most efficient imprinted DFB lasers reported; and long operational lifetimes (under ambient conditions) of ∼12 × 104 pump pulses. The key for their successful operation has been the selection of a highly efficient and stable dye, perylene orange (PDI-O), and a proper matrix to host it, the fluoro-modified thermoplastic resist mr-I7030R, which has enabled 2D imprinting while preserving the dye optical properties. The use of the UV-curable resist SU8 as an alternative matrix for PDI-O to be imprinted by combined nanoimprint and photolithography was also investigated, and was concluded to be unsuccessful due to severe photoluminescence quenching. By replacing PDI-O with Rhodamine 6G, lasers with reasonable thresholds, but with significantly inferior operational lifetimes in comparison to PDI-O/mr-I7030R devices, were obtained., We thank support from the Spanish Government (MINECO) and the European Community (FEDER) through Grants MAT2011-28167-C02 and MAT2015-66586-R, as well as to the University of Alicante. M.M-V. has been partly supported by a MINECO FPI fellowship (no. BES-2009-020747) and by a Junta de Castilla y León grant (no. SA046U16).

In the present work thermal-nanoimprint lithography of various commercial thermoplastic resists as matrixes for perylenediimides (PDIs) has been studied. This fabrication method reduces the number of fabrication steps, and therefore, the cost of the obtained distributed feedback (DFB) lasers. The optical properties of these devices are analyzed, aiming to optimize their performance. Spanish Government (MINECO) and the European Community (FEDER) through grants MAT2008-06648-C02 and MAT-2011-28167-C02. Manuel G. Ramírez is supported by a CSIC fellowship within the program JAE.

Efficient ASE at wavelengths >620 nm from PS films doped with a bay-substituted perylenediimide (PDI) derivative is reported. The maximum PDI content is around 40 times larger than in prior studies. The ability to introduce large dye amounts into the film without photoluminescence (PL) quenching allows very high PL and ASE efficiencies with low thresholds. A distributed feedback (DFB) laser device using one of the best-performing films is fabricated and characterized. We thank support from the Spanish Government (MINECO), the European Community (FEDER) and the Generalitat Valenciana through MAT-2011–28167-C02, CTQ2011–26455, PROMETEO 2012/010 and ISIC/2012/008, as well as to the University of Alicante and the University Miguel Hernández de Elche.

Amplified spontaneous emission (ASE) is observed, under optical pump, in polystyrene films doped with two pentathienoacene derivatives functionalised with thienyl-S,S-dioxide groups (compounds 2 and 3). The effect of the dioxide groups on the ASE properties is analysed by comparing the performance with that of its corresponding non-oxidized analogue (1). Films containing either 2 or 3 show ASE at 511 and 574 nm, respectively, when excited directly (at 435 nm) on their absorption bands, showing thresholds and linewidths larger than those obtained from films doped with 1, pumped at 355 nm. ASE is also observed under excitation at 355 nm, in samples containing 1 (host) and either 2 or 3 (guests), due to energy transfer from host to guest. For the blends with 3, the ASE threshold is lower than that obtained when the films are excited directly. Results are interpreted in terms of the photophysical parameters such as absorption capacity, fluorescence efficiency, singlet-to-triplet intersystem crossing leading to triplet-triplet re-absorptions, bimolecular energy-transfer efficiency, efficiency of internal conversion process, etc. State-of-the-art quantum chemical calculations are used in the interpretation of the experimental results. Authors from the University of Alicante acknowledge support from the Spanish Government (MINECO) and the European Community (FEDER) through grants MAT2008–06648-C02–01 and MAT2011–28167-C02–01. The work at the University of Málaga is supported by the MEC projects CTQ2012–33733 and by the PO9–4708 project by the Junta de Andalucía. Raquel Rondão acknowledges FCT for a PhD grant (SFRH/BD/38882/2007). D.A.S.F. gratefully acknowledges the financial support from the Brazilian Research Councils: CAPES, CNPq (grant 303084/2010–3) and FAP-DF (Fundação de Apoio à Pesquisa do Distrito Federal).

Thin film organic lasers represent attractive light sources for numerous applications. Currently, efforts are devoted to the development of low-cost high-performance and color-tunable devices, whereby both the resonator and the active layer should consist of solution-processable organic materials. Herein, solution-processed distributed-feedback lasers are reported with polymeric resonators on top of active films of perylene orange or carbon-bridged oligo(p-phenylenevinylene) dispersed in polystyrene, which combine these properties. These lasers emit in the 520–595 nm range and show low thresholds (≈1 kW cm−2) and long operational lifetimes (7 × 105 pump pulses), which are comparable to other state-of-the-art lasers that contain the same active materials but resonators made on inorganic substrates. Due to this top-layer resonator configuration, the laser slope efficiencies of the present devices are remarkably superior. A centimeter-size device emitting at different wavelengths within a broad spectral range, based on a perylene-based film of uniform thickness that contributes to preserve a low threshold, is demonstrate, MINECO. Grant Numbers: MAT2011-28167-C02-01, MAT2015-66586-R, BES-2009-020747 Junta de Castilla y León. Grant Number: SA046U16 MEXT. Grant Numbers: 16H04106, 15H05754

This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N´-bis(3-methylphenyl)-N,N´-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature.

Two critical temperatures, T1 and T2, which limit the range of the photorefractive (PR) response of polymer composites, have been determined from temperature dependence studies of the ac conductivity. T1 represents the calorimetric glass transition temperature and sets the level under which chromophore orientation is drastically reduced. T2 sets the level above which conduction mechanisms become dominated by temperature. In this study, we stress the importance of the T2 parameter, generally ignored in literature, and the advantages of using dielectric spectroscopy to obtain both critical temperatures from a single experiment. In addition, impurity diffusion processes, which play an important role in PR property optimization, have been identified from the frequency dependence of the ac conductivity.

This review compiles the work performed in the field of organic solid-state lasers with the hole-transporting organic molecule N,N´-bis(3-methylphenyl)-N,N´-diphenyl-benzidine system (TPD), in view of improving active laser material properties. The optimization of the amplified spontaneous emission characteristics, i.e., threshold, linewidth, emission wavelength and photostability, of polystyrene films doped with TPD in waveguide configuration has been achieved by investigating the influence of several materials parameters such as film thickness and TPD concentration. In addition, the influence in the emission properties of the inclusion of a second-order distributed feedback grating in the substrate is discussed.

It is shown that the photorefractive (PR) performance of polymer composites based on poly(N-vinylcarbazole) can be improved when samples are subjected to an electric field for a certain time, i.e. conditioned, previous to the PR characterization. It is also found that for conditioned samples the addition of an organic ionic liquid to the PR composition allows to obtain PR effect without the need of using a sensitizer. The typical electric field treatment time at room temperature and at a field of 20 V µm−1 is 20 min. This procedure leads to a decrease of dark conductivity and an increase of photoconductivity, and consequently an increase of conductivity contrast. This results in higher PR two-beam-coupling gain coefficients and shorter response times, particularly at low fields. Dependencies of the process dynamics on impurities, applied field strength, temperature and the presence of an organic ionic liquid are examined in detail. It is remarkable the significant increase of the PR gain coefficients, and more drastically of the net gain coefficients, observed at low fields (

Solution-processed polymer films are used in multiple technological applications. The presence of residual solvent in the film, as a consequence of the preparation method, affects the material properties, so films are typically subjected to post-deposition thermal annealing treatments aiming at its elimination. Monitoring the amount of solvent eliminated as a function of the annealing parameters is important to design a proper treatment to ensure complete solvent elimination, crucial to obtain reproducible and stable material properties and therefore, device performance. Here we demonstrate, for the first time to our knowledge, the use of an organic distributed feedback (DFB) laser to monitor with high precision the amount of solvent extracted from a spin-coated polymer film as a function of the thermal annealing time. The polymer film of interest, polystyrene in the present work, is doped with a small amount of a laser dye as to constitute the active layer of the laser device and deposited over a reusable DFB resonator. It is shown that solvent elimination translates into shifts in the DFB laser wavelength, as a consequence of changes in film thickness and refractive index. The proposed method is expected to be applicable to other types of annealing treatments, polymer-solvent combinations or film deposition methods, thus constituting a valuable tool to accurately control the quality and reproducibility of solution-processed polymer thin films. The work was supported by the Spanish Government (MINECO) and the European Community (FEDER) through grant No. MAT-2011-28167-C02-01. M.M.-V. has been partly supported by a MINECO FPI fellowship (No. BES-2009-020747).

The human epidermal growth factor receptor 2 (ErbB2) protein plays an important role in human malignancies. Its overexpression has been recognized as a feature of a malignant cancerous phenotype in breast cancer cell lines, and has become one of the most widely investigated clinical indicators of breast, ovarian, gastrointestinal and lung cancers. In this work a vertically emitting organic distributed feedback (DFB) laser has been used to detect the ErbB2 protein. This DFB laser consists of a polystyrene (PS) film containing a perylenediimide laser dye, deposited over a second-order one dimensional grating fabricated on fused silica by thermal-nanoimprint lithography and subsequent reactive ion etching processes. Specificity of the system to ErbB2 protein biomarker, achieved by functionalizing the PS with anti-ErbB2 monoclonal antibodies, is demonstrated. A concentration limit of detection for ErbB2 protein of 14 ng/mL has been obtained, and no cross-reactivity has been observed with bovine serum albumin (BSA) and tumor necrosis factor alpha (TNFα) proteins. These findings open the possibility of using this type of biosensors in clinical applications. This work was supported by the Spanish Government (MINECO) and the European Community (FEDER) through grant no. MAT-2011–28167-C02. This work was partially funded by the Basque Government within the framework of the Etortek Program (Grant No. IE13-360). M. Morales-Vidal has been partly supported by a MINECO FPI fellowship (no. BES-2009-020747).

The photorefractive (PR) properties, via photoconductivity, birefringence and two-beam-coupling experiments, of a composite containing a fullerene–trinitrofluorenone (C 60 –TNF) dyad in which the two moieties are linked by a conformationally flexible polyether chain are reported. The PR performance of this compound as a sensitizer in polymer composites based on poly( N -vinylcarbazole) (PVK) as hole charge transporter, piperidindicyanostyrene (PDCST) as non-linear optical chromophore and butyl benzyl phthalate (BBP) as plasticizer, has been compared to those of the corresponding C 60 and TNF derivatives. Results show that the linkage of C 60 and TNF leads to an improvement in the photoconductivity of the composite leading to an increase of the PR speed.

The aim of this work was to design strategies to improve the performance of solid-state lasers and amplifiers based on perylenediimide (PDI) derivatives as active materials. So, the effect of different types of modifications of the chemical structure of PDIs in their spectral, electrochemical, and laser properties in both solution and PDI-doped polystyrene films at various concentrations has been investigated. In particular, we focused on controlling the wavelength of emission in order to tune the laser wavelength as well as in increasing the amount of PDI in the films in order to decrease the laser thresholds, while keeping a good photostability. Three types of modifications of the chemical structure were investigated: (a) symmetrical substitution at the imide nitrogen positions (PDI 1); (b) substitution at the bay positions in the PDI core (PDI 4); and (c) modification in the dicarboximide group (PDI 5). All three derivatives were soluble and showed good n-type acceptor ability. Routes b and c led to r...

Amplified spontaneous emission (ASE) in dye-doped mesostructured silica films, deposited directly over fused silica substrates, is demonstrated with low thresholds. Due to functionalization of the silica network with phenyl groups, the refractive index of the active layer is sufficiently increased to impart waveguiding properties that lead to highly efficient ASE. Such functionalization eliminates the need for a separate low-refractive-index layer between the active film and the substrate, as is often used to achieve waveguiding properties with silica mesostructured materials, though which is typically accompanied by significant optical losses that reduce overall ASE performance. By forming a high-quality waveguide without the need for a separate low-refractive-index layer, significantly improved properties are obtained, with ASE thresholds as low as 8 kW cm−2. Solid-state 2D NMR spectroscopy measurements establish the compositions and structures of the active mesostructured film at a molecular level, in particular that phenyl functionalization of the mesochannel surfaces promotes the homogeneous dispersion of the laser dye species over nanoscale dimensions in the materials. The authors thank support from the Spanish Government through the “Ministerio de Economía y Competitividad” (MINECO) and the European Community (FEDER) through grant nos. MAT2008–06648-C02 and MAT2011–28167-C02. M.G.R. has been supported by a CSIC fellowship within the program JAE. M.A.D.G. acknowledges funding received from the “Ministerio de Educación y Ciencia, MEC” (reference no. PR2009–0456) to perform a research stay at UCSB to initiate the collaboration between the two teams contributing to this work. M.J.N.J. acknowledges financial support from the Alexander von Humboldt-Foundation through a Feodor Lynen Research Fellowship. The NMR experiments were conducted in the Central Facilities of the UCSB Materials Research Laboratory supported by the MRSEC program of the U.S. NSF under award no. DMR-1121053. The work at UCSB was supported by the USARO through the Institute for Collaborative Biotechnologies through W911NF-09-D-0001.

Thin film organic lasers represent a new generation of inexpensive, mechanically flexible devices for spectroscopy, optical communications and sensing. For this purpose, it is desired to develop highly efficient, stable, wavelength-tunable and solution-processable organic laser materials. Here we report that carbon-bridged oligo(p-phenylenevinylene)s serve as optimal materials combining all these properties simultaneously at the level required for applications by demonstrating amplified spontaneous emission and distributed feedback laser devices. A series of six compounds, with the repeating unit from 1 to 6, doped into polystyrene films undergo amplified spontaneous emission from 385 to 585 nm with remarkably low threshold and high net gain coefficients, as well as high photostability. The fabricated lasers show narrow linewidth (105 pump pulses for oligomers with three to six repeating units) and wavelength tunability across the visible spectrum (408–591 nm)., Thin film organic solid-state lasers are low-cost flexible devices which require efficient, stable, colour-tunable, solution-processable materials. Here, the authors show that oligo(p-phenylenevinylene)s simultaneously possess all such properties, as demonstrated by their use in laser devices.

Distributed feedback (DFB) laser sensors with active films consisting of a highly efficient and photostable perylenediimide dye (perylene orange, PDI-O) dispersed in polysytrene (PS), used as passive matrix, are reported. PDIdoped- PS DFB lasers show an excellent operational durability under ambient conditions, superior to those of previously reported DFBs used for sensing purposes. Their bulk refractive index sensing capabilities, under exposure to liquids of different refractive index, have been determined from changes in their emission wavelength. The role of the active film thickness on both, the laser and the sensing performance, has been explored. The use of a thick active film (850 nm) allows obtaining the lowest possible threshold and highest operational lifetime for this type of device although the sensor sensitivity is lower than that achievable with a thin film (160 nm). It is also shown that the inclusion of a high refractive index TiO2 layer on top of the sensor structure allows improving the sensor sensitivity by around two times. This work was supported by the Spanish Government (MINECO) and the European Community (FEDER) through grant no. MAT-2011–28167-C02. M.M-V. has been partly supported by a MINECO FPI fellowship (no. BES-2009-020747).

The refractive index sensing capabilitity of distributed feedback (DFB) lasers based on highly photostable (under ambient conditions) perylenediimide-based active films, are reported. The sensor bulk sensitivity is determined from changes in the laser emission wavelength upon exposure to different liquids. The role of the active film thickness (hf) on the sensor sensitivity and on the laser parameters is studied. Sensors based on very thin films (hf = 160 nm) show the highest sensitivities, but their laser thresholds are relatively high and their operational durabilities moderate. The use of thicker films (hf = 850 nm) allows reducing the laser threshold and increasing the durability by two orders of magnitude. In this case, a higher sensitivity is achieved when the sensor operates at the wavelength corresponding to the first-order TE1 mode, instead of at the TE0 one. Finally, it is also shown that the inclusion of a high refractive index TiO2 layer on top of the sensor structure improves the sensitivity by around two times. This work was supported by the Spanish Government (MINECO) and the European Community (FEDER) through grant no. MAT-2011–28167-C02. This work was partially funded by the Basque Government within the framework of the Etortek Program (Grant No. IE13-360). M. Morales-Vidal has been partly supported by a MINECO FPI fellowship (no. BES-2009-020747).

The concentration dependence of amplified spontaneous emission (ASE) in optically pumped polystyrene (PS) films containing a variable concentration (between 2.5 and 100 wt%) of the luminescent and hole-transporting organic molecule N , N ′-Bis(3-methylphenyl)- N , N ′-diphenylbenzidine (TPD) is reported. It is observed that both, the ASE threshold and linewidth above threshold, decrease with concentration up to 20 wt% doped films and then keeps a constant value up to concentrations of 100 wt% (neat films). Accordingly, photoluminescence (PL) efficiency increases with concentration up to 20 wt% and then saturates. Results also show that the position of ASE can be tuned between 413 and 421 nm by changing the concentration of TPD. These shifts are also observed in the PL emission and are presumably due to the increase of absorption, as well as polarity of the medium, with concentration. Measurements and modeling of the waveguiding characteristics of the films, show that the observed shifts are not due to cut-off thickness limitations. In addition, although the different confinement of the waveguide modes might be influencing the ASE performance, it seems to be determined mostly by the PL efficiency. Results show that the most efficient films are those doped with 20–30 wt% TPD. Finally, a study of the photostability of the samples is also included.

Laser action at 420 nm is observed in photopumped polymer films of polystyrene (PS) doped with the hole-transporting organic molecule N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine (TPD). Measurements of the dependence of signal on the length of the pump stripe show that the mechanism responsible for the observed spectral collapse is amplified spontaneous emission (ASE). By fitting the evolution of the output intensity at 420 nm with the excitation length, gain coefficients up to 16 cm-1 are measured.

A series of novel trinitrofluorenone−C60 acceptors in which the two subunits are placed at different distances have been prepared and their electrochemical and photorefractive properties measured. The photorefractive performance of these compounds as sensitizers in polymer composites based on poly(N-vinylcarbazole) is similar to that of C60, but with shorter response times and slightly lower gain coefficients. Since the substitution of C60 by these novel trinitrofluorenone−C60 systems leads to a reduction of losses due to beam fanning, larger voltages could be applied, resulting in larger gain coefficients.

Thin film organic lasers (TFOLs) represent a new generation of inexpensive, mechanically flexible devices with demonstrated applicability in numerous applications in the fields of spectroscopy, optical communications and sensing requiring an organic, efficient, stable, wavelength-tunable and solution-processable laser material. A distributed feedback (DFB) laser is a particularly attractive TFOL because it shows single mode emission, low pump energy, easy integration with other devices, mechanical flexibility and potentially low production cost. Here, amplified spontaneous emission (ASE) and DFB laser applications of novel high performing perylene dyes and p-phenylenevinylene (PV) oligomers, both dispersed in thermoplastic polymers, used as passive matrixes, are reported. Second-order DFB lasers based on these materials show single mode emission, wavelength tunability across the visible spectrum, operational lifetimes of >105 pump pulses, larger than previously reported PV oligomers or polymers, and thresholds close to pumping requirements with light-emitting diodes. This work was supported by the Spanish Government (MINECO) and the European Community (FEDER) through grant no. MAT-2011–28167-C02. M. Morales-Vidal has been partly supported by a MINECO FPI fellowship (no. BES-2009-020747).