ABSTRACT
Exciton binding energy (Eb) is understood as the energy required to dissociate an exciton in free-charge carriers, and is known to be an important parameter in determining the performance of organic opto-electronic devices. However, the development of a molecular design to achieve a small level of Eb in the solid state continues to lag behind. Here, to investigate the relationship between aggregation and Eb, star-shaped π-conjugated compounds DBC-RD and TPE-RD were developed using dibenzo[g,p]chrysene (DBC) and tetraphenylethylene (TPE). Theoretical calculations and physical measurements in solution showed no apparent differences between DBC-RD and TPE-RD, indicating that these molecules possess similar properties on a single-molecule level. By contrast, pristine films incorporating these molecules showed significantly different levels of electron affinity, ionization potential, and optical gap. Also, DBC-RD had a smaller Eb value of 0.24 eV compared with that of TPE-RD (0.42 eV). However, these molecules showed similar Eb values under dispersed conditions, which suggested that the decreased Eb of DBC-RD in pristine film is induced by molecular aggregation. By comparison with TPE-RD, DBC-RD showed superior performances in single-component organic solar cells and organic photocatalysts. These results indicate that a molecular design suitable for aggregation is important to decrease the Eb in films.
ABSTRACT
There is a growing demand for the development of novel solar power systems that can simultaneously solve the problems associated with both energy generation and food supply in agriculture. Green-light wavelength-selective organic solar cells (OSCs), whose transmitted blue and red light can be utilized to promote plant growth were recently reported by our group. However, the influence of wavelength variation on the photosynthetic rate in green-light wavelength-selective OSCs remains unclear. In this study, we report on the design and synthesis of new electron-accepting π-conjugated molecules containing cyclopentene-annelated thiophene with a spiro-substituted 2,7-bis(2-ethylhexyl)fluorene (FT) unit (TT-FT-ID) as a green-light wavelength-selective nonfullerene acceptor along with a reference compound TT-T-ID. Photophysical measurements indicate that the introduction of the FT unit leads to an absorption band with a small full width at half maximum in films, leading to the ability to fine-tune the absorption length. Concerning the optimization of the conditions for the fabrication of the active layers, which are composed of a green-light wavelength-selective donor polymer of poly(3-hexylthiophene) (P3HT) and the new acceptors, Bayesian optimization based on Gaussian process regression was applied to minimize the experimental batches. The green-light wavelength-selective factor (SG) and the PCEs in the green-light region (PCE-GR) of the P3HT:TT-FT-ID-based device were determined to be 0.52 and 8.6%, respectively, which are higher values than those of the P3HT:TT-T-ID blend film. The P3HT:TT-FT-ID blend film increased the photosynthetic rate of green pepper compared to that of the P3HT:TT-T-ID blend film. These results indicate that the fine-tuning of the absorbance required for crop growth is an important issue in developing green-light wavelength-selective OSCs for agrivoltaics.
ABSTRACT
Correction for 'Phosphaacene as a structural analogue of thienoacenes for organic semiconductors' by Kyohei Matsuo et al., Chem. Commun., 2022, 58, 13576-13579, https://doi.org/10.1039/D2CC05122B.
ABSTRACT
An air-stable λ3-phosphinine-containing polycyclic aromatic compound without steric protection was synthesized and its charge transport properties were evaluated, which revealed moderate hole mobility. This research is the first experimental demonstration of the organic electronic applications of low-coordinate phosphorus compounds.
ABSTRACT
To achieve a complete closed-shell quinoidal state, bis(dicyanomethylene)-substituted quinoidal terthiophenes bearing benzene annelation at all thiophene rings were synthesized using a retro-Diels-Alder reaction as the key step. The unique structures and properties originating from the full benzene annelation were revealed by X-ray analysis as well as property measurements. Organic solar cells based on the combination of a donor polymer with a quinoidal terthiophene as an acceptor showed a power conversion efficiency of 1.39%.
ABSTRACT
Electron-donor function of methanofullerenes (MFs) in bulk heterojunction systems is demonstrated by the combination of MFs with the electron-transporting π-system that has a much higher electron affinity than MFs.
ABSTRACT
The synthesis of three-dimensional compounds containing perylene bis(dicarboximide) for application as acceptor materials in organic photovoltaics is reported. Physicochemical measurements as well as device evaluations revealed that the characteristic properties of these materials are derived from their three-dimensional structure.
