Impact of Semiconductor Band Tails and Band Filling on Photovoltaic Efficiency Limits

A new side-chain C60-fullerene functionalized thiophene copolymer bearing tributylphosphine-substituted hexylic lateral groups was successfully synthesized by means of a fast and effective post-polymerization reaction on a regioregular ω-alkylbrominated polymeric precursor. The growth of the polymeric intermediate was followed by NMR spectrometry in order to determine the most convenient reaction time. The obtained copolymer was soluble in water and polar solvents and was used as a photoactive layer in single-material organic photovoltaic (OPV) solar cells. The copolymer photovoltaic efficiency was compared with that of an OPV cell containing a water-soluble polythiophenic homopolymer, functionalized with the same tributylphosphine-substituted hexylic side chains, in a blend with a water-soluble C60-fullerene derivative. The use of a water-soluble double-cable copolymer made it possible to enhance the control on the nanomorphology of the active blend, thus reducing phase-segregation phenomena, as well as the macroscale separation between the electron acceptor and donor components. Indeed, the power conversion efficiency of OPV cells based on a single material was higher than that obtained with the classical architecture, involving the presence of two distinct ED and EA materials (PCE: 3.11% vs. 2.29%, respectively). Moreover, the synthetic procedure adopted to obtain single material-based cells is more straightforward and easier than that used for the preparation of the homopolymer-based BHJ solar cell, thus making it possible to completely avoid the long synthetic pathway which is required to prepare water-soluble fullerene derivatives.

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Generalized Boltzmann relations in semiconductors including band tails

Journal of Applied Physics ◽

10.1063/5.0037432 ◽

2021 ◽

Vol 129 (4) ◽

pp. 045701

Author(s):

Arnout Beckers ◽

Dominique Beckers ◽

Farzan Jazaeri ◽

Bertrand Parvais ◽

Christian Enz

Keyword(s):

Band Tails

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Importance of $${{d}}_{{{xy}}}$$ orbital and electron correlation in iron-based superconductors revealed by phase diagram for 1111-system

Scientific Reports ◽

10.1038/s41598-021-89231-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Tsuyoshi Kawashima ◽

Shigeki Miyasaka ◽

Hirokazu Tsuji ◽

Takahiro Yamamoto ◽

Masahiro Uekubo ◽

...

Keyword(s):

Electron Correlation ◽

Weak Coupling ◽

Structural Parameters ◽

Structural Flexibility ◽

Superconducting Transition ◽

Iron Based Superconductors ◽

Wide Range ◽

Band Filling ◽

Iron Based ◽

Correlation Strength

AbstractThe structural flexibility at three substitution sites in LaFeAsO enabled investigation of the relation between superconductivity and structural parameters over a wide range of crystal compositions. Substitutions of Nd for La, Sb or P for As, and F or H for O were performed. All these substitutions modify the local structural parameters, while the F/H-substitution also changes band filling. It was found that the superconducting transition temperature $$T_{\text{c}}$$ T c is strongly affected by the pnictogen height $$h_{Pn}$$ h Pn from the Fe-plane that controls the electron correlation strength and the size of the $$d_{xy}$$ d xy hole Fermi surface (FS). With increasing $$h_{Pn}$$ h Pn , weak coupling BCS superconductivity switches to the strong coupling non-BCS one where electron correlations and the $$d_{xy}$$ d xy hole FS may be important.

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Three dimensional band-filling control of complex oxides triggered by interfacial electron transfer

Nature Communications ◽

10.1038/s41467-021-22790-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Meng Meng ◽

Yuanwei Sun ◽

Yuehui Li ◽

Qichang An ◽

Zhenzhen Wang ◽

...

Keyword(s):

Electron Transfer ◽

Field Effect ◽

Essential Role ◽

Field Effect Transistors ◽

Three Dimensional ◽

Complex Oxides ◽

Band Filling ◽

Local Lattice ◽

Oxygen Migration ◽

Oxide Heterostructure

AbstractThe d-band-filling of transition metals in complex oxides plays an essential role in determining their structural, electronic and magnetic properties. Traditionally, at the oxide heterointerface, band-filling control has been achieved via electrostatic modification in the structure of field-effect transistors or electron transfer, which is limited to the quasi-two-dimension at the interface. Here we report a three-dimensional (3D) band-filling control by changing the local lattice coordination in a designed oxide heterostructure. At the LaCoO3/LaTiO3 heterointerface, due to the Fermi level mismatch, electrons transfer from LaTiO3 to LaCoO3. This triggers destabilisation of the CoO6 octahedrons, i.e. the formation of lattice configurations with a reduced Co valence. The associated oxygen migration results in the 3D topotactic phase transition of LaCoO3. Tuned by the thickness of LaTiO3, different crystalline phases and band-fillings of Co occur, leading to the emergence of different magnetic ground states.

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Zum paramagnetischen Verhalten von Palladium/Silber/Eisen- Legierungen/ On the Paramagnetic Behaviour of Palladium-Silver-Iron Alloys

Zeitschrift für Naturforschung A ◽

10.1515/zna-1975-0512 ◽

1975 ◽

Vol 30 (5) ◽

pp. 645-655

Author(s):

Peter Brill

Keyword(s):

Electron Concentration ◽

Magnetic Moments ◽

Alloy Series ◽

Band Filling ◽

Paramagnetic Behaviour ◽

Field Coefficient ◽

Saturation Moment ◽

Molecular Field Coefficient ◽

The Moment ◽

Curie Temperatures

Abstract The paramagnetic susceptibility of four PdAgFe alloy series containing 1, 3, 5 and 7 at. % Fe have been measured between 20° and 150 °C. On the basis of a band filling model the local moment contribution to the susceptibility has been evaluated according to a Curie -Weiss law. Assuming that the iron atoms donate 3 electrons and the silver atoms 1 electron to the Pd 4d band, the effective magnetic moments and the paramagnetic Curie temperatures of all the alloys can be represented by a single curve against the electron concentration. The effective magnetic moment is consistent with an Fe moment of 5.92 μB localized on the iron sites and a Pd moment varying with electron concentration and temperature. The same turns out to be true for the ferromagnetic region where the saturation moment, obtained on PdFe alloys and a PdAgFe alloy by different authors, is considered to arise from a localized Fe moment of 5 μB and a concentration dependent Pd moment. The molecular field coefficient for the interaction between the Fe moments and the Pd 4d electrons is found to be 850 mol/cm3 at 385 K and 1200 mol/cm3 at 0 K. Finally, the iron moment suggested in this work is contrasted with the moment derived from neutron diffraction measurements.

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