Unraveling the Temperature Dependence of Exciton Dissociation and Free Charge Generation in Nonfullerene Organic Solar Cells

Due to the barrierless free charge generation, low charge trapping, and high charge mobilities, the PM6:Y6 organic solar cell (OSC) achieves excellent power conversion efficiency (PCE) of 15.7%. However, the...

Download Full-text

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

Nature Communications ◽

10.1038/s41467-020-19332-5 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 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.

Download Full-text

Ultrafast Charge Generation Enhancement in Nanoscale Polymer Solar Cells with DIO Additive

Nanomaterials ◽

10.3390/nano10112174 ◽

2020 ◽

Vol 10 (11) ◽

pp. 2174

Author(s):

Tongchao Shi ◽

Zeyu Zhang ◽

Xia Guo ◽

Zhengzheng Liu ◽

Chunwei Wang ◽

...

Keyword(s):

Solar Cells ◽

Vibrational Relaxation ◽

Transient Absorption ◽

Polymer Solar Cells ◽

Acid Methyl Ester ◽

Free Charge ◽

Exciton Dissociation ◽

Charge Generation ◽

Carrier Generation ◽

Acid Methyl

We study the ultrafast photoexcitation dynamics in PBDTTT-C-T (P51, poly(4,8-bis(5-(2-ethylhexyl)-thiophene-2-yl)-benzo[1,2-b:4,5-b′]dithiophene-alt-alkylcarbonyl-thieno[3,4-b]thiophene)) film (~100 nm thickness) and PBDTTT-C-T:PC71BM (P51:PC71BM, phenyl-C71-butyric-acid-methyl ester) nanostructured blend (∼100 nm thickness) with/without DIO(1,8-diiodooctane) additives with sub-10 fs transient absorption (TA). It is revealed that hot-exciton dissociation and vibrational relaxation could occur in P51 with a lifetime of ~160 fs and was hardly affected by DIO. However, the introduction of DIO in P51 brings a longer lifetime of polaron pairs, which could make a contribution to photocarrier generation. In P51:PC71BM nanostructured blends, DIO could promote the Charge Transfer (CT) excitons and free charges generation with a ~5% increasement in ~100 fs. Moreover, the dissociation of CT excitons is faster with DIO, showing a ~5% growth within 1 ps. The promotion of CT excitons and free charge generation by DIO additive is closely related with active layer nanomorphology, accounting for Jsc enhancement. These results reveal the effect of DIO on carrier generation and separation, providing an effective route to improve the efficiency of nanoscale polymer solar cells.

Download Full-text

Single particle dual plasmonic effect for efficient organic solar cells

Applied Nanoscience ◽

10.1007/s13204-020-01641-2 ◽

2021 ◽

Author(s):

Adi Prasetio ◽

Soyeon Kim ◽

Muhammad Jahandar ◽

Dong Chan Lim

Keyword(s):

Solar Cells ◽

Organic Solar Cells ◽

Light Absorption ◽

Resonance Effect ◽

Localized Surface Plasmon ◽

Main Role ◽

Charge Generation ◽

One Pot ◽

Wide Range ◽

Light Reflectance

AbstractIncorporating localized surface plasmon resonance (LSPR) into organic solar cells (OSCs) is a popular method for improving the power conversion efficiency (PCE) by introducing better light absorption. In this work, we designed a one-pot synthesis of Ag@SiO2@AuNPs dual plasmons and observed an immense increase in light absorption over a wide range of wavelengths. Ag@SiO2 plays the main role in enhancing light absorption near the ultraviolet band. The silica shell can also further enhance the LSP resonance effect and prevent recombination on the surface of AgNPs. The AuNPs on the Ag@SiO2 shell exhibited strong broad visible-light absorption due to LSP resonance and decreased light reflectance. By utilizing Ag@SiO2@AuNPs, we could enhance the light absorption and photoinduced charge generation, thereby increasing the device PCE to 8.57% and Jsc to 17.67 mA cm−2, which can be attributed to the enhanced optical properties. Meanwhile, devices without LSPR nanoparticles and Ag@SiO2 LSPR only showed PCEs of 7.36% and 8.18%, respectively.

Download Full-text

Rational compatibility in ternary matrix enables all-small-molecule organic solar cells with over 16% efficiency

Energy & Environmental Science ◽

10.1039/d1ee00496d ◽

2021 ◽

Author(s):

Mengyun Jiang ◽

Hairui Bai ◽

Hongfu Zhi ◽

Lu Yan ◽

Han Young Woo ◽

...

Keyword(s):

Solar Cells ◽

Phase Separation ◽

Small Molecule ◽

Organic Solar Cells ◽

Charge Generation ◽

Molecular Arrangement ◽

Efficient Charge

How to manipulate the phase separation and molecular arrangement to meet the need of efficient charge generation and extraction remains as the long-standing challenge in all-small-molecule organic solar cells (ASM-OSCs)....

Download Full-text

Conditions for efficient charge generation preceded by energy transfer process in non-fullerene organic solar cells

Journal of Materials Chemistry A ◽

10.1039/d1ta06698f ◽

2021 ◽

Author(s):

L. Benatto ◽

C. A. M. Moraes ◽

G. Candiotto ◽

K. R. A. Sousa ◽

J. P. A. Souza ◽

...

Keyword(s):

Energy Transfer ◽

Solar Cells ◽

Binding Energy ◽

Transfer Process ◽

Organic Solar Cells ◽

Driving Force ◽

Energy Transfer Process ◽

Simple Relationship ◽

Charge Generation ◽

Efficient Charge

Our results provide a simple relationship involving the driving force and binding energy of CT state to maximize charge generation in non-fullerene organic solar cells.

Download Full-text

Uphill and downhill charge generation from charge transfer to charge separated states in organic solar cells

Journal of Materials Chemistry C ◽

10.1039/d1tc02351a ◽

2021 ◽

Author(s):

Shahidul Alam ◽

Vojtech Nádaždy ◽

Tomáš Váry ◽

Christian Friebe ◽

Rico Meitzner ◽

...

Keyword(s):

Cyclic Voltammetry ◽

Solar Cells ◽

Charge Transfer ◽

Energy Level ◽

Density Of States ◽

Organic Solar Cells ◽

Joint Density ◽

Charge Generation ◽

Donor Acceptor

Energy level alignments at the organic donor–acceptor interface cannot be predicted from cyclic voltammetry. Onsets for joint density of states and charge generation, reveal cases of energy uphill and – newly observed – downhill charge generation.

Download Full-text

Diffusion-enhanced exciton dissociation in single-material organic solar cells

Physical Chemistry Chemical Physics ◽

10.1039/d1cp03328j ◽

2021 ◽

Vol 23 (37) ◽

pp. 20848-20853

Author(s):

Nong V. Hoang ◽

Vasileios C. Nikolis ◽

Lukasz Baisinger ◽

Koen Vandewal ◽

Maxim S. Pshenichnikov

Keyword(s):

Solar Cells ◽

Organic Solar Cells ◽

Domain Boundary ◽

Exciton Dissociation ◽

Dissociation Efficiency ◽

Single Material

Multiple crossings at the domain boundary with different molecular orientations enhance the exciton dissociation efficiency in single-material organic solar cells.

Download Full-text

Synergistic Concurrent Enhancement of Charge Generation, Dissociation, and Transport in Organic Solar Cells with Plasmonic Metal-Carbon Nanotube Hybrids

Advanced Materials ◽

10.1002/adma.201404248 ◽

2014 ◽

Vol 27 (9) ◽

pp. 1519-1525 ◽

Cited By ~ 67

Author(s):

Ju Min Lee ◽

Joonwon Lim ◽

Nayeun Lee ◽

Hyung Il Park ◽

Kyung Eun Lee ◽

...

Keyword(s):

Solar Cells ◽

Carbon Nanotube ◽

Organic Solar Cells ◽

Charge Generation

Download Full-text

Organic and nano-structured composite photovoltaics: An overview

Journal of Materials Research ◽

10.1557/jmr.2005.0407 ◽

2005 ◽

Vol 20 (12) ◽

pp. 3167-3179 ◽

Cited By ~ 152

Author(s):

Sophie E. Gledhill ◽

Brian Scott ◽

Brian A. Gregg

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Organic Semiconductors ◽

Organic Solar Cells ◽

Organic Materials ◽

Low Cost ◽

Open Circuit ◽

Charge Generation ◽

Dye Sensitized ◽

Excitonic Solar Cells

Organic photovoltaic devices are poised to fill the low-cost, low power niche in the solar cell market. Recently measured efficiencies of solid-state organic cells are nudging 5% while Grätzel’s more established dye-sensitized solar cell technology is more than double this. A fundamental understanding of the excitonic nature of organic materials is an essential backbone for device engineering. Bound electron-hole pairs, “excitons,” are formed in organic semiconductors on photo-absorption. In the organic solar cell, the exciton must diffuse to the donor–accepter interface for simultaneous charge generation and separation. This interface is critical as the concentration of charge carriers is high and recombination here is higher than in the bulk. Nanostructured engineering of the interface has been utilized to maximize organic materials properties, namely to compensate the poor exciton diffusion lengths and lower mobilities. Excitonic solar cells have different limitations on their open-circuit photo-voltages due to these high interfacial charge carrier concentrations, and their behavior cannot be interpreted as if they were conventional solar cells. This article briefly reviews some of the differences between excitonic organic solar cells and conventional inorganic solar cells and highlights some of the technical strategies used in this rapidly progressing field, whose ultimate aim is for organic solar cells to be a commercial reality.

Download Full-text