scholarly journals Critical Role of H-Aggregation for High-Efficiency Photoinduced Charge Generation in Pristine Pentamethine Cyanine Salts

2021 ◽  
Author(s):  
George Cameron Fish ◽  
Juan Manuel Moreno-Naranjo ◽  
Andreas Billion ◽  
Daniel Kratzert ◽  
Erwin Hack ◽  
...  
Keyword(s):  
High Efficiency ◽  
Transient Absorption ◽  
Critical Role ◽  
Optoelectronic Devices ◽  
Transient Absorption Spectroscopy ◽  
Organic Photovoltaic ◽  
Charge Generation ◽  
Femtosecond Transient Absorption ◽  
Photoinduced Charge

The mechanism of photoinduced symmetry-breaking charge separation in solid cyanine salts at the base of organic photovoltaic and optoelectronic devices is still debated. Here, we employ femtosecond transient absorption spectroscopy...

scholarly journals Optical Gain in Semiconducting Polymer Nano and Mesoparticles

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1138
Author(s):  
Mark Geoghegan ◽  
Marta M. Mróz ◽  
Chiara Botta ◽  
Laurie Parrenin ◽  
Cyril Brochon ◽  
...  
Keyword(s):  
Near Infrared ◽  
Transient Absorption ◽  
Optical Gain ◽  
Stimulated Emission ◽  
Transient Absorption Spectroscopy ◽  
Charge Generation ◽  
Charge Formation ◽  
Femtosecond Transient Absorption ◽  
Uv Excitation ◽  
Nanoparticle Film

The presence of excited-states and charge-separated species was identified through UV and visible laser pump and visible/near-infrared probe femtosecond transient absorption spectroscopy in spin coated films of poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles. Optical gain in the mesoparticle films is observed after excitation at both 400 and 610 nm. In the mesoparticle film, charge generation after UV excitation appears after around 50 ps, but little is observed after visible pump excitation. In the nanoparticle film, as for a uniform film of the pure polymer, charge formation was efficiently induced by UV excitation pump, while excitation of the low energetic absorption states (at 610 nm) induces in the nanoparticle film a large optical gain region reducing the charge formation efficiency. It is proposed that the different intermolecular interactions and molecular order within the nanoparticles and mesoparticles are responsible for their markedly different photophysical behavior. These results therefore demonstrate the possibility of a hitherto unexplored route to stimulated emission in a conjugated polymer that has relatively undemanding film preparation requirements.

scholarly journals Photoinduced charge recombination in dipolar D–A–A photonic liquid crystal polymorphs

2017 ◽  
Vol 19 (6) ◽  
pp. 4588-4596 ◽  
Author(s):  
Mercedes M. A. Mazza ◽  
Shiori Yamazaki ◽  
Dieu X. Mai ◽  
Suyog Padgaonkar ◽  
Samuel Peurifoy ◽  
...  
Keyword(s):  
Thin Films ◽  
Liquid Crystal ◽  
Absorption Spectroscopy ◽  
Liquid Crystalline ◽  
Transient Absorption ◽  
Charge Recombination ◽  
Transient Absorption Spectroscopy ◽  
Femtosecond Transient Absorption ◽  
Femtosecond Transient Absorption Spectroscopy ◽  
Photoinduced Charge

A hexylalkoxy dipolar D–A–A molecule has been synthesized and the photophysics studied via femtosecond transient absorption spectroscopy (FsTA) in toluene and in amorphous and liquid crystalline spherulite thin films.

The critical role of the coordination sphere in the high-efficiency blue-light emission from aminopyrazine metal-organic polymers

2021 ◽  
Vol 186 ◽  
pp. 109025
Author(s):  
João Humberto Dias Campos ◽  
Meiry Edivirges Alvarenga ◽  
Maykon Alves Lemes ◽  
José Antônio do Nascimento Neto ◽  
Freddy Fernandes Guimarães ◽  
...  
Keyword(s):  
Blue Light ◽  
Coordination Sphere ◽  
High Efficiency ◽  
Light Emission ◽  
Critical Role ◽  
Organic Polymers ◽  
Blue Light Emission ◽  
Metal Organic

scholarly journals Ultrafast nonequilibrium dynamic process of separate electron and hole during exciton formation in few-layer tungsten disulfide

2021 ◽  
Author(s):  
Junjie Chen ◽  
Sen Guo ◽  
Dabin Lin ◽  
Zhaogang Nie ◽  
Chung-Che Huang ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Dynamic Process ◽  
Formation Process ◽  
Transient Absorption ◽  
Tungsten Disulfide ◽  
Transient Absorption Spectroscopy ◽  
Femtosecond Transient Absorption ◽  
Nonequilibrium Dynamic ◽  
Femtosecond Transient Absorption Spectroscopy ◽  
Separate Electron

Femtosecond transient absorption spectroscopy has been employed to unravel separate initial nonequilibrium dynamic process of photo-injected electrons and holes during the formation process of the lowest excitons at the K-valley...

scholarly journals The role of spin in the degradation of organic photovoltaics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ivan Ramirez ◽  
Alberto Privitera ◽  
Safakath Karuthedath ◽  
Anna Jungbluth ◽  
Johannes Benduhn ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Bulk Heterojunction ◽  
Critical Factor ◽  
Model Systems ◽  
Transient Absorption Spectroscopy ◽  
Triplet States ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
A Charge

AbstractStability is now a critical factor in the commercialization of organic photovoltaic (OPV) devices. Both extrinsic stability to oxygen and water and intrinsic stability to light and heat in inert conditions must be achieved. Triplet states are known to be problematic in both cases, leading to singlet oxygen production or fullerene dimerization. The latter is thought to proceed from unquenched singlet excitons that have undergone intersystem crossing (ISC). Instead, we show that in bulk heterojunction (BHJ) solar cells the photo-degradation of C60 via photo-oligomerization occurs primarily via back-hole transfer (BHT) from a charge-transfer state to a C60 excited triplet state. We demonstrate this to be the principal pathway from a combination of steady-state optoelectronic measurements, time-resolved electron paramagnetic resonance, and temperature-dependent transient absorption spectroscopy on model systems. BHT is a much more serious concern than ISC because it cannot be mitigated by improved exciton quenching, obtained for example by a finer BHJ morphology. As BHT is not specific to fullerenes, our results suggest that the role of electron and hole back transfer in the degradation of BHJs should also be carefully considered when designing stable OPV devices.

scholarly journals SnSe Nanosheets: From Facile Synthesis to Applications in Broadband Photodetections

Nanomaterials ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 49
Author(s):  
Xiangyang Li ◽  
Zongpeng Song ◽  
Huancheng Zhao ◽  
Wenfei Zhang ◽  
Zhenhua Sun ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Ultrafast Optics ◽  
Light Response ◽  
Transient Absorption Spectroscopy ◽  
Monolayer Graphene ◽  
Proof Of Concept ◽  
Facile Synthesis ◽  
Femtosecond Transient Absorption ◽  
Potential Applications ◽  
Promising Area

In recent years, using two-dimensional (2D) materials to realize broadband photodetection has become a promising area in optoelectronic devices. Here, we successfully synthesized SnSe nanosheets (NSs) by a facile tip ultra-sonication method in water-ethanol solvent which was eco-friendly. The carrier dynamics of SnSe NSs was systematically investigated via a femtosecond transient absorption spectroscopy in the visible wavelength regime and three decay components were clarified with delay time of τ1 = 0.77 ps, τ2 = 8.3 ps, and τ3 = 316.5 ps, respectively, indicating their potential applications in ultrafast optics and optoelectronics. As a proof-of-concept, the photodetectors, which integrated SnSe NSs with monolayer graphene, show high photoresponsivities and excellent response speeds for different incident lasers. The maximum photo-responsivities for 405, 532, and 785 nm were 1.75 × 104 A/W, 4.63 × 103 A/W, and 1.52 × 103 A/W, respectively. The photoresponse times were ~22.6 ms, 11.6 ms, and 9.7 ms. This behavior was due to the broadband light response of SnSe NSs and fast transportation of photocarriers between the monolayer graphene and SnSe NSs.

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