scholarly journals Adjusting the energy of interfacial states in organic photovoltaics for maximum efficiency

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nicola Gasparini ◽  
Franco V. A. Camargo ◽  
Stefan Frühwald ◽  
Tetsuhiko Nagahara ◽  
Andrej Classen ◽  
...  
Keyword(s):  
Organic Solar Cells ◽  
Charge Separation ◽  
High Performance ◽  
Driving Forces ◽  
Maximum Efficiency ◽  
Free Carriers ◽  
Exciton Splitting ◽  
Interfacial States ◽  
Optimal Adjustment ◽  
Interfacial Charge

AbstractA critical bottleneck for improving the performance of organic solar cells (OSC) is minimising non-radiative losses in the interfacial charge-transfer (CT) state via the formation of hybrid energetic states. This requires small energetic offsets often detrimental for high external quantum efficiency (EQE). Here, we obtain OSC with both non-radiative voltage losses (0.24 V) and photocurrent losses (EQE > 80%) simultaneously minimised. The interfacial CT states separate into free carriers with ≈40-ps time constant. We combine device and spectroscopic data to model the thermodynamics of charge separation and extraction, revealing that the relatively high performance of the devices arises from an optimal adjustment of the CT state energy, which determines how the available overall driving force is efficiently used to maximize both exciton splitting and charge separation. The model proposed is universal for donor:acceptor (D:A) with low driving forces and predicts which D:A will benefit from a morphology optimization for highly efficient OSC.

scholarly journals Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Ture F. Hinrichsen ◽  
Christopher C. S. Chan ◽  
Chao Ma ◽  
David Paleček ◽  
Alexander Gillett ◽  
...  
Keyword(s):  
Solar Cells ◽  
Charge Transfer ◽  
Organic Solar Cells ◽  
Charge Separation ◽  
Free Charge ◽  
Charge Generation ◽  
Time Resolved ◽  
Thermodynamic Conditions ◽  
Donor Acceptor ◽  
Interfacial Charge

Abstract Organic solar cells based on non-fullerene acceptors can show high charge generation yields despite near-zero donor–acceptor energy offsets to drive charge separation and overcome the mutual Coulomb attraction between electron and hole. Here, we use time-resolved optical spectroscopy to show that free charges in these systems are generated by thermally activated dissociation of interfacial charge-transfer states that occurs over hundreds of picoseconds at room temperature, three orders of magnitude slower than comparable fullerene-based systems. Upon free electron–hole encounters at later times, both charge-transfer states and emissive excitons are regenerated, thus setting up an equilibrium between excitons, charge-transfer states and free charges. Our results suggest that the formation of long-lived and disorder-free charge-transfer states in these systems enables them to operate closely to quasi-thermodynamic conditions with no requirement for energy offsets to drive interfacial charge separation and achieve suppressed non-radiative recombination.

Designing high performance all-small-molecule solar cells with non-fullerene acceptors: comprehensive studies on photoexcitation dynamics and charge separation kinetics

2018 ◽  
Vol 11 (1) ◽  
pp. 211-220 ◽  
Author(s):  
Junqing Shi ◽  
Anna Isakova ◽  
Abasi Abudulimu ◽  
Marius van den Berg ◽  
Oh Kyu Kwon ◽  
...  
Keyword(s):  
Solar Cells ◽  
Small Molecule ◽  
Organic Solar Cells ◽  
Charge Separation ◽  
High Performance ◽  
High Definition ◽  
Definition Of ◽  
Separation Kinetics ◽  
Comprehensive Studies

High definition of all-small molecule materials for organic solar cells allows slow separation of localized charges.

Nanometer-Scaled Landscape of Polymer:Fullerene Blends Mapped with Visible s-SNOM

2021 ◽  
Author(s):  
Ya-Rong Lee ◽  
Cheng-Chia Huang ◽  
Wen-Yu Huang ◽  
Chin-Ti Chen ◽  
Ping-Tsung Huang ◽  
...  
Keyword(s):  
Active Layer ◽  
Organic Solar Cells ◽  
Charge Separation ◽  
High Performance ◽  
Bulk Heterojunction ◽  
Near Field ◽  
Photovoltaic Performance ◽  
Energy Landscapes ◽  
Donor And Acceptor ◽  
Shed Light

Abstract Bulk heterojunction is one key concept leading to breakthrough in organic photovoltaics. The active layer is expectantly formed of distinct morphologies that carry out their respective roles in photovoltaic performance. The morphology-performance relationship however remains stymied, because unequivocal morphology at the nanoscale is not available. We used scattering-type scanning near-field optical microscopy operating with a visible light source (visible s-SNOM) to disclose the nanomorphology of P3HT:PCBM and pBCN:PCBM blends. Donor and acceptor domain as well as intermixed phase were identified and their intertwined distributions were mapped. We proposed energy landscapes of the BHJ active layer to shed light on the roles played by these morphologies in charge separation, transport and recombination. This study shows that visible s-SNOM is capable of profiling the morphological backdrop pertaining to the operation of high performance organic solar cells.

High-Performance and Low-Energy Loss Organic Solar Cells with Non-fused Ring Acceptor by Alkyl Chain Engineering

2021 ◽  
pp. 129768
Author(s):  
Dou Luo ◽  
Xue Lai ◽  
Nan Zheng ◽  
Chenghao Duan ◽  
Zhaojin Wang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Energy Loss ◽  
Organic Solar Cells ◽  
High Performance ◽  
Alkyl Chain ◽  
Low Energy ◽  
Fused Ring

A Facile Synthesized Polymer Featuring B‐N Covalent Bond and Small Singlet‐Triplet Gap for High‐Performance Organic Solar Cells

2021 ◽  
Vol 60 (16) ◽  
pp. 8813-8817
Author(s):  
Shuting Pang ◽  
Zhiqiang Wang ◽  
Xiyue Yuan ◽  
Langheng Pan ◽  
Wanyuan Deng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Organic Solar Cells ◽  
High Performance ◽  
Covalent Bond

scholarly journals High performance tandem organic solar cells via a strongly infrared-absorbing narrow bandgap acceptor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhenrong Jia ◽  
Shucheng Qin ◽  
Lei Meng ◽  
Qing Ma ◽  
Indunil Angunawela ◽  
...  
Keyword(s):  
Solar Cells ◽  
Power Conversion Efficiency ◽  
Conversion Efficiency ◽  
Organic Solar Cells ◽  
High Performance ◽  
Short Circuit ◽  
Power Conversion ◽  
High Power Conversion Efficiency ◽  
Device Structure ◽  
Narrow Bandgap

AbstractTandem organic solar cells are based on the device structure monolithically connecting two solar cells to broaden overall absorption spectrum and utilize the photon energy more efficiently. Herein, we demonstrate a simple strategy of inserting a double bond between the central core and end groups of the small molecule acceptor Y6 to extend its conjugation length and absorption range. As a result, a new narrow bandgap acceptor BTPV-4F was synthesized with an optical bandgap of 1.21 eV. The single-junction devices based on BTPV-4F as acceptor achieved a power conversion efficiency of over 13.4% with a high short-circuit current density of 28.9 mA cm−2. With adopting BTPV-4F as the rear cell acceptor material, the resulting tandem devices reached a high power conversion efficiency of over 16.4% with good photostability. The results indicate that BTPV-4F is an efficient infrared-absorbing narrow bandgap acceptor and has great potential to be applied into tandem organic solar cells.

Alcohol-soluble fluorene derivate functionalized with pyridyl groups as a high-performance cathode interfacial material in organic solar cells

2021 ◽  
Author(s):  
Lin Lin ◽  
Zeping Huang ◽  
Yuanqi Luo ◽  
Tingen Peng ◽  
Baitian He ◽  
...  
Keyword(s):  
Solar Cells ◽  
Organic Photovoltaics ◽  
Organic Solar Cells ◽  
High Performance ◽  
Fluorene Derivative ◽  
Interfacial Material ◽  
Cathode Interlayer

The synthesis and application as a cathode interlayer in organic photovoltaics of a fluorene derivative with pyridyl functional chains are presented.

scholarly journals Comparative Study of the Field Performances of Pressure-Grouted Micropiles Using Gravity and Packers

2021 ◽  
Vol 11 (15) ◽  
pp. 6736
Author(s):  
Ong Heo ◽  
Yeowon Yoon ◽  
Jinung Do
Keyword(s):  
Urban Areas ◽  
High Performance ◽  
Driving Forces ◽  
Field Performance ◽  
Underground Space ◽  
Creep Tests ◽  
Deep Foundation ◽  
Installation Depth ◽  
Pressure Grouting ◽  
The One

When underground space requires excavation in areas below the water table, the foundation system suffers from buoyancy, which leads to the uplifting of the superstructure. A deep foundation system can be used; however, in cases where a hard layer is encountered, high driving forces and corresponding noises cause civil complaints in urban areas. Micropiles can be an effective alternative option, due to their high performance despite a short installation depth. Pressurized grouting is used with a packer to induce higher interfacial properties between micropile and soil. In this study, the field performance of micropiles installed using gravitational grouting or pressure-grouted using either a geotextile packer or rubber packer was comparatively evaluated by tension and creep tests. Micropiles were installed using pressure grouting in weak and fractured zones. As results, the pressure-grouted micropiles showed more stable and stronger behaviors than ones installed using the gravitational grouting. Moreover, the pressure-grouted micropile installed using the rubber packer showed better performance than the one using the geotextile packer.

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