scholarly journals A universal Urbach rule for disordered organic semiconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Christina Kaiser ◽  
Oskar J. Sandberg ◽  
Nasim Zarrabi ◽  
Wei Li ◽  
Paul Meredith ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Disordered Systems ◽  
Urbach Energy ◽  
Phonon Scattering ◽  
Exponential Tail ◽  
Temperature Dependent ◽  
Static Disorder ◽  
Line Shapes ◽  
Gaussian Density

AbstractIn crystalline semiconductors, absorption onset sharpness is characterized by temperature-dependent Urbach energies. These energies quantify the static, structural disorder causing localized exponential-tail states, and dynamic disorder from electron-phonon scattering. Applicability of this exponential-tail model to disordered solids has been long debated. Nonetheless, exponential fittings are routinely applied to sub-gap absorption analysis of organic semiconductors. Herein, we elucidate the sub-gap spectral line-shapes of organic semiconductors and their blends by temperature-dependent quantum efficiency measurements. We find that sub-gap absorption due to singlet excitons is universally dominated by thermal broadening at low photon energies and the associated Urbach energy equals the thermal energy, regardless of static disorder. This is consistent with absorptions obtained from a convolution of Gaussian density of excitonic states weighted by Boltzmann-like thermally activated optical transitions. A simple model is presented that explains absorption line-shapes of disordered systems, and we also provide a strategy to determine the excitonic disorder energy. Our findings elaborate the meaning of the Urbach energy in molecular solids and relate the photo-physics to static disorder, crucial for optimizing organic solar cells for which we present a revisited radiative open-circuit voltage limit.

scholarly journals A Universal Urbach Rule for Disordered Organic Semiconductors

2021 ◽  
Author(s):  
Christina Kaiser ◽  
Oskar Sandberg ◽  
Nasim Zarrabi ◽  
Wei Li ◽  
Paul Meredith ◽  
...  
Keyword(s):  
Spectral Line ◽  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Urbach Energy ◽  
Transfer Model ◽  
Exponential Tail ◽  
Temperature Dependent ◽  
Static Disorder ◽  
Line Shapes ◽  
Gaussian Density

Abstract In crystalline semiconductors, the sharpness of the absorption spectrum onset is characterized by temperature-dependent Urbach energies. These energies quantify the static, structural disorder causing localized exponential tail states, and the dynamic disorder due to electron-phonon scattering. The applicability of this exponential-tail model to molecular and amorphous solids has long been debated. Nonetheless, exponential fittings are routinely applied to the analysis of the sub-gap absorption of organic semiconductors alongside Gaussian-like spectral line-shapes predicted by non-adiabatic Marcus theory. Herein, we elucidate the sub-gap spectral line-shapes of organic semiconductors and their blends by temperature-dependent quantum efficiency measurements in photovoltaic structures. We find that the Urbach energy associated with singlet excitons universally equals the thermal energy regardless of static disorder. These observations are consistent with absorption spectra obtained from a convolution of Gaussian density of excitonic states weighted by a Boltzmann factor. A generalized Marcus charge transfer model is presented that explains the absorption spectral line-shape of disordered molecular matrices, and we also provide a simple strategy to determine the excitonic disorder energy. Our findings elaborate the true meaning of the dynamic Urbach energy in molecular solids and deliver a way of relating the photo-physics to static disorder, crucial for optimizing molecular electronic devices such as organic solar cells.

scholarly journals Synthesis and Theoretical Investigation Using DFT of 2,3-Diphenylquinoxaline Derivatives for Electronic and Photovoltaic Effects

2021 ◽  
Author(s):  
Dorota Zając ◽  
Dariusz Przybylski ◽  
Jadwiga Sołoducho
Keyword(s):  
Solar Cells ◽  
Acrylic Acid ◽  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Molecular Design ◽  
Low Cost ◽  
Design Synthesis ◽  
Semiconducting Properties ◽  
Homo Lumo

AbstractDeveloping effective and low‐cost organic semiconductors is an opportunity for the development of organic solar cells (OPV). Herein, we report the molecular design, synthesis and characterization of two molecules with D–A–D–A configuration: 2-cyano-3-(5-(8-(3,4-ethylenodioxythiophen-5-yl)-2,3-diphenylquinoxalin-5-yl)thiophen-2-yl)acrylic acid (6) and 2-cyano-3-(5-(2,3-diphenyl-8-(thiophen-2-yl)quinoxalin-5-yl)thiophen-2-yl)acrylic acid (7). Moreover, we investigated the structural, theoretical and optical properties. The distribution of HOMO/LUMO orbitals and the values of the ionization potential indicate good semiconducting properties of the compounds and that they can be a bipolar material. Also, the optical study show good absorption in visible light (λabs 380–550 nm). We investigate the theoretical optoelectronic properties of obtained compounds as potential materials for solar cells.

Star-shaped organic semiconductors with planar triazine core and diketopyrrolopyrrole branches for solution-processed small-molecule organic solar cells

2015 ◽  
Vol 115 ◽  
pp. 35-49 ◽  
Author(s):  
Sheng-Yi Shiau ◽  
Chun-Ho Chang ◽  
Wei-Jen Chen ◽  
Hsing-Ju Wang ◽  
Ru-Jong Jeng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Organic Semiconductors ◽  
Small Molecule ◽  
Organic Solar Cells ◽  
Solution Processed

Solar Cell Manufacturing Method with the Structure of the Bulk Heterojunction Based on Organic Semiconductors with a Direct Architecture

2016 ◽  
Vol 845 ◽  
pp. 224-227 ◽  
Author(s):  
Danila Saranin ◽  
Marina Orlova ◽  
Sergey Didenko ◽  
Oleg Rabinovich ◽  
Andrey Kryukov
Keyword(s):  
Solar Cells ◽  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Fill Factor ◽  
Research Output ◽  
Bulk Heterojunction ◽  
Organic Basis ◽  
Manufacturing Method ◽  
Current Voltage ◽  
Current Voltage Characteristics

This article presents the results of research output voltage characteristics of solar cells on an organic basis with the use of P3HT: PCBM system. There were produced organic solar cells in a coating in air, current-voltage characteristics were measured. It was determined the characteristic influence of a substrate cleaning and annealing temperature of layers applied on fill factor and conversion efficiency.

On Razors Edge: Influence of the Source Insulator Edge on the Charge Transport of Vertical Organic Field Effect Transistors

MRS Advances ◽  
2017 ◽  
Vol 2 (23) ◽  
pp. 1249-1257 ◽  
Author(s):  
F. Michael Sawatzki ◽  
Alrun A. Hauke ◽  
Duy Hai Doan ◽  
Peter Formanek ◽  
Daniel Kasemann ◽  
...  
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Field Effect Transistors ◽  
Electrical Power ◽  
Strong Impact ◽  
Organic Field Effect Transistor ◽  
Effect Transistor

ABSTRACTTo benefit from the many advantages of organic semiconductors like flexibility, transparency, and small thickness, electronic devices should be entirely made from organic materials. This means, additionally to organic LEDs, organic solar cells, and organic sensors, we need organic transistors to amplify, process, and control signals and electrical power. The standard lateral organic field effect transistor (OFET) does not offer the necessary performance for many of these applications. One promising candidate for solving this problem is the vertical organic field effect transistor (VOFET). In addition to the altered structure of the electrodes, the VOFET has one additional part compared to the OFET – the source-insulator. However, the influence of the used material, the size, and geometry of this insulator on the behavior of the transistor has not yet been examined. We investigate key-parameters of the VOFET with different source insulator materials and geometries. We also present transmission electron microscopy (TEM) images of the edge area. Additionally, we investigate the charge transport in such devices using drift-diffusion simulations and the concept of a vertical organic light emitting transistor (VOLET). The VOLET is a VOFET with an embedded OLED. It allows the tracking of the local current density by measuring the light intensity distribution.We show that the insulator material and thickness only have a small influence on the performance, while there is a strong impact by the insulator geometry – mainly the overlap of the insulator into the channel. By tuning this overlap, on/off-ratios of 9x105 without contact doping are possible.

Organic and nano-structured composite photovoltaics: An overview

2005 ◽  
Vol 20 (12) ◽  
pp. 3167-3179 ◽  
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.

scholarly journals Temperature dependent characteristics of poly(3 hexylthiophene)-fullerene based heterojunction organic solar cells

2003 ◽  
Vol 93 (6) ◽  
pp. 3376-3383 ◽  
Author(s):  
D. Chirvase ◽  
Z. Chiguvare ◽  
M. Knipper ◽  
J. Parisi ◽  
V. Dyakonov ◽  
...  
Keyword(s):  
Solar Cells ◽  
Organic Solar Cells ◽  
Temperature Dependent

The phonon scattering mechanism and its effect on temperature dependent thermal and thermoelectric properties of the silver nanowire

2022 ◽  
Author(s):  
Gui-Cang He ◽  
Lina Shi ◽  
Yilei Hua ◽  
Xiao-Li Zhu
Keyword(s):  
Thermoelectric Properties ◽  
Phonon Scattering ◽  
Silver Nanowire ◽  
Scattering Mechanism ◽  
Temperature Dependent ◽  
Scattering Mechanisms ◽  
Phonon Structure

In this work, the electron-phonon, the phonon-phonon, and phonon structure scattering mechanisms and the effect on the thermal and thermoelectric properties of the silver nanowire (AgNW) are investigated in temperature...

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