Real-Time Tracking of Polymer Crystallization Dynamics in Organic Bulk Heterojunctions by Raman Microscopy

State-of-the-art organic photovoltaic active layers typically undergo post-treatment such as thermal or solvent vapor annealing to increase their performance by tuning the bulk heterojunction morphology. Molecular crystallinity is one of the key factors that determine the morphology. Real-time tracking of the crystallinity during the post-treatment is strongly desired for understanding the physics of the crystallization process and for optimizing the post-treatment protocol. Here, we report on the cold crystallization (CC) dynamics of the polymer in the temperature range of 50-150 degrees C in polymer:fullerene blends based on poly(3-hexylthiophene) with various fullerene-based acceptors (C-60, PC61BM, PC71BM, bisPC(61)BM, HBIM, AIM8, and IrC60) in real-time by Raman microscopy. We also reveal how different solvents, fullerene acceptors, and temperatures affect CC during thermal annealing. We further demonstrate a correlation between the fullerene derivative weight and the polymer crystallinity for the as-cast films and also a correlation of the polymer crystallinity before and after annealing. Our findings are essential for developing efficient strategies of morphology optimization in emerging organic photovoltaic devices with real-time Raman microscopy tracking as a valuable tool

Long-range exciton transport in brightly fluorescent furan/phenylene co-oligomer crystals

The design of light-emitting crystalline organic semiconductors for optoelectronic applications requires a thorough understanding of the singlet exciton transport process. In this study, we show that the singlet exciton diffusion length in a promising semiconductor crystal based on furan/phenylene co-oligomers is 24 nm. To achieve this, we employed the photoluminescence quenching technique using a specially synthesized quencher, which is a long furan/phenylene co-oligomer that was facilely implanted into the host crystal lattice. Extensive Monte-Carlo simulations, exciton-exciton annihilation experiments and numerical modelling fully supported our findings. We further demonstrated the high potential of the furan/phenylene co-oligomer crystals for light-emitting applications by fabricating solution-processed organic light emitting transistors

Dual Optoelectronic Organic Field-Effect Device: Combination of Electroluminescence and Photosensitivity

Merging the functionality of an organic field-effect transistor (OFET) with either a light emission or a photoelectric effect can increase the efficiency of displays or photosensing devices. In this work, we show that an organic semiconductor enables a multifunctional OFET combining electroluminescence (EL) and a photoelectric effect. Specifically, our computational and experimental investigations of a six-ring thiophene-phenylene co-oligomer (TPCO) revealed that this material is promising for OFETs, light-emitting, and photoelectric devices because of the large oscillator strength of the lowest-energy singlet transition, efficient luminescence, pronounced delocalization of the excited state, and balanced charge transport. The fabricated OFETs showed a photoelectric response for wavelengths shorter than 530 nm and simultaneously EL in the transistor channel, with a maximum at ~570 nm. The devices demonstrated an EL external quantum efficiency (EQE) of ~1.4% and a photoelectric responsivity of ~0.7 A W–1, which are among the best values reported for state-of-the-art organic light-emitting transistors and phototransistors, respectively. We anticipate that our results will stimulate the design of efficient materials for multifunctional organic optoelectronic devices and expand the potential applications of organic (opto)electronics

CCDC 1851983: Experimental Crystal Structure Determination

Related Article: Artur A. Mannanov, Maxim S. Kazantsev, Anatoly D. Kuimov, Vladislav G. Konstantinov, Dmitry I. Dominskiy, Vasiliy A. Trukhanov, Daniil S. Anisimov, Nikita V. Gultikov, Vladimir V. Bruevich, Igor P. Koskin, Alina A. Sonina, Tatyana V. Rybalova, Inna K. Shundrina, Evgeny A. Mostovich, Dmitry Yu. Paraschuk, Maxim S. Pshenichnikov|2019|J.Mater.Chem.C|7|60|doi:10.1039/c8tc04151