scholarly journals Electronic Structure and Surface Properties of Copper Thiocyanate: A Promising Hole Transport Material for Organic Photovoltaic Cells

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5765
Author(s):  
Bonaventure A. Odeke ◽  
Gyang D. Chung ◽  
Jesutofunmi A. Fajemisin ◽  
Kabir S. Suraj ◽  
Denis K. Tonui ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Solar Cells ◽  
Dimethyl Sulfoxide ◽  
Valence Band ◽  
Surface Properties ◽  
Density Functional ◽  
Power Conversion ◽  
Hole Transport ◽  
Excitation Energies ◽  
X Ray

Considering the significance of hexagonal copper thiocyanate (β-CuSCN) in several optoelectronic technologies and applications, it is essential to investigate its electronic structure and surface properties. Herein, we have employed density functional theory (DFT) calculations to characterise the band structure, density of states, and the energy-dependent X-ray photoelectron (XPS) valence band spectra at variable excitation energies of β-CuSCN. The surface properties in the absence and presence of dimethyl sulfoxide (DMSO), a solvent additive for improving perovskite solar cells’ power conversion efficiency, have also been systematically characterised. β-CuSCN is shown to be an indirect band gap material (Eg = 3.68 eV) with the valence band edge demonstrated to change from being dominated by Cu-3d at soft X-ray ionisation photon energies to Cu-3p at hard X-ray ionisation photon energies. The adsorption energy of dimethyl sulfoxide (DMSO) on the (100) and (110) β-CuSCN surfaces is calculated at −1.12 and −0.91 eV, respectively. The presence of DMSO on the surface is shown to have a stabilisation effect, lowering the surface energy and tuning the work function of the β-CuSCN surfaces, which is desirable for organic solar cells to achieve high power conversion efficiencies.

scholarly journals Efficient Molecular Modelling of Butterfly-Shaped Hole Transport Materials With Remarkable Photovoltaic Properties For High-Performance Organic Solar Cells

2021 ◽  
Author(s):  
Muhammad Yasir Mehboob ◽  
Muhammad Adnan ◽  
Riaz Hussain ◽  
Zobia Irshad
Keyword(s):  
Solar Cells ◽  
Density Of States ◽  
Organic Solar Cells ◽  
Density Functional ◽  
Transition Density ◽  
Open Circuit ◽  
Hole Transport ◽  
Excitation Energies ◽  
Strong Electron ◽  
Photovoltaic Properties

Abstract Currently, organic solar cells (OSCs) with non-fullerene electron acceptors offer the highest efficiencies among all reported OSCs. To further improve the efficiencies and stabilities of fullerene-free organic solar cells, end-capped acceptor variations is built with strong electron withdrawing groups. In this report, we have theoretically calculated five new butterfly-shaped fullerene-free acceptors (FD1-FD6) by making end-capped modifications on reference molecule (R) with the purpose to study the improvement in photophysical, opto-electronic, and photo-voltaic properties of newly designed molecules by employing density functional theory (DFT) and time dependent (TD-DFT). Besides, some properties like position of frontier molecular orbitals (FMOs), excitation and binding energy, hole-electron overlap, density of states, overlap density of states, molecular electrostatic potential, open circuit voltage, transition density matrix, and reorganizational energy of electron and hole are also considered and associated with experimentally synthesized reference compound. All calculated molecules displayed a good red-shifting with high charge mobility of electrons among low binding and excitation energies as opposed to reference molecule. Furthermore, all designed molecules (FD1-FD6) and the reference R shows narrow band-gap along-with great charge shifting capability. This theoretical framework proves that end-capped acceptors variation is a modest and effective strategy to accomplish the desirable opto-electronic properties. Therefore, FD1-FD6 are suggested to experimentalist for out-looking future developments to fabricate highly efficient solar cells devices.

scholarly journals First-principles insights into the electronic structure, optical and band alignment properties of earth-abundant Cu2SrSnS4 solar absorber

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nelson Y. Dzade
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Valence Band Maximum ◽  
Band Alignment ◽  
Excitation Energies ◽  
Promising Alternative ◽  
Earth Abundant

AbstractCu2SrSnS4 (CSTS) is a promising alternative candidate to Cu2ZnSnS4 (CZTS) for single- or multi-junction photovoltaics (PVs) owing to its efficient light-absorbing capability, earth-abundant, nontoxic constituents, and suitable defect properties. However, as a novel absorber material, several fundamental properties need to be characterized before further progress can be made in CSTS photovoltaics. In this letter, hybrid density functional theory (DFT) calculations have been used to comprehensively characterize for the first time, the electronic structure, band alignment, and optical properties of CSTS. It is demonstrated that CSTS possesses the ideal electronic structure (direct band gap of 1.98 eV and small photocarrier effective masses) and optical properties (high extinction coefficient and wide absorption) suitable for photovoltaic applications. Simulated X-ray photoelectron spectroscopy (XPS) valence band spectra using variable excitation energies show that Cu-3d electronic state dominates the valence band maximum of CSTS. Furthermore, the vacuum-aligned band diagram between CSTS and other common absorbers (CZTS, CIGS, CdTe) and the common n-type partner materials (CdS, ZnO) was constructed, which indicate staggered type-II band alignment at the CSTS/CdS and CSTS/ZnO interfaces. Based on these results, interface band offset engineering and alternative device architectures are suggested to improve charge carrier separation and power conversion efficiencies of CSTS.

scholarly journals In Depth Analysis of Photovoltaic Performance of Chlorophyll Derivative-Based “All Solid-State” Dye-Sensitized Solar Cells

Molecules ◽  
2020 ◽  
Vol 25 (1) ◽  
pp. 198 ◽  
Author(s):  
Michèle Chevrier ◽  
Alberto Fattori ◽  
Laurent Lasser ◽  
Clément Kotras ◽  
Clémence Rose ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solid State ◽  
Density Functional ◽  
Photovoltaic Performance ◽  
Dye Sensitized Solar Cells ◽  
Hole Transport ◽  
Tio2 Electrode ◽  
Dye Sensitized ◽  
Depth Analysis ◽  
Sensitized Solar Cells

Chlorophyll a derivatives were integrated in “all solid-state” dye sensitized solar cells (DSSCs) with a mesoporous TiO2 electrode and 2′,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin dyes, a systematic investigation was carried out in order to elucidate their main limitations. To provide a comprehensive understanding of the parameters (structure, nature of the anchoring group, adsorption …) and their relationship with the PCEs, density functional theory (DFT) calculations, optical and photovoltaic studies and electron paramagnetic resonance analysis exploiting the 4-carboxy-TEMPO spin probe were combined. The recombination kinetics, the frontier molecular orbitals of these DSSCs and the adsorption efficiency onto the TiO2 surface were found to be the key parameters that govern their photovoltaic response.

scholarly journals Graphene assisted crystallization and charge extraction for efficient and stable perovskite solar cells free of a hole-transport layer

RSC Advances ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 4417-4424
Author(s):  
Ahmed Esmail Shalan ◽  
Mustafa K. A. Mohammed ◽  
Nagaraj Govindan
Keyword(s):  
Solar Cells ◽  
Power Conversion ◽  
Perovskite Solar Cells ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Transport Layer ◽  
Energy Research ◽  
Power Sources ◽  
New Era ◽  
Photovoltaic Power

In recent times, perovskite solar cells (PSCs) have been of wide interest in solar energy research, which has ushered in a new era for photovoltaic power sources through the incredible enhancement in their power conversion efficiency (PCE).

How big is big? Separation by conventional methods, X-ray and electronic structures of positional isomers of bis-tert-butylisocyano adduct of 2(3),9(10),16(17),23(24)-tetrachloro-3(2),10(9),17(16),24(23)-tetra(2,6-di-iso-propylphenoxy)-phthalocyaninato iron(II) complex

2016 ◽  
Vol 20 (01n04) ◽  
pp. 337-351 ◽  
Author(s):  
Derrick R. Anderson ◽  
Pavlo V. Solntsev ◽  
Hannah M. Rhoda ◽  
Victor N. Nemykin
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Positional Isomers ◽  
Excitation Energies ◽  
Functional Theory ◽  
X Ray ◽  
Vertical Excitation ◽  
X Ray Crystallography ◽  
Tddft Calculations ◽  
Insight Into

A presence of bulky 2,6-di-iso-propylphenoxy groups in bis-tert-butylisocyano adduct of 2(3),9(10),16(17),23(24)-tetrachloro-3(2),10(9),17(16),24(23)-tetra(2,6-di-iso-propylphenoxy)-phthalocyaninato iron(II) complex allows separation of two individual positional isomers and a mixture of the remaining two isomers using conventional chromatography. X-ray structures of “[Formula: see text]” and “[Formula: see text]” isomers were confimed by X-ray crystallography. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of each individual positional isomer allowed insight into their electronic structures and vertical excitation energies, which were correlated with the experimental UV-vis and MCD spectra.

scholarly journals Closely packed, low reorganization energy π-extended postfullerene acceptors for efficient polymer solar cells

2018 ◽  
Vol 115 (36) ◽  
pp. E8341-E8348 ◽  
Author(s):  
Steven M. Swick ◽  
Weigang Zhu ◽  
Micaela Matta ◽  
Thomas J. Aldrich ◽  
Alexandra Harbuzaru ◽  
...  
Keyword(s):  
Solar Cells ◽  
Density Functional ◽  
High Efficiency ◽  
Performance Metrics ◽  
Polymer Solar Cells ◽  
Reorganization Energy ◽  
Grazing Incidence ◽  
Scanning Calorimetry ◽  
Quantum Chemical Analysis ◽  
X Ray

New organic semiconductors are essential for developing inexpensive, high-efficiency, solution-processable polymer solar cells (PSCs). PSC photoactive layers are typically fabricated by film-casting a donor polymer and a fullerene acceptor blend, with ensuing solvent evaporation and phase separation creating discrete conduits for photogenerated holes and electrons. Until recently, n-type fullerene acceptors dominated the PSC literature; however, indacenodithienothiophene (IDTT)-based acceptors have recently enabled remarkable PSC performance metrics, for reasons that are not entirely obvious. We report two isomeric IDTT-based acceptors 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz-(5, 6)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]di-thiophene (ITN-C9) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz(6,7)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITzN-C9) that shed light on the exceptional IDTT properties vis-à-vis fullerenes. The neat acceptors and blends with fluoropolymer donor poly{[4,8-bis[5-(2- ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF) are investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry, single-crystal X-ray diffraction, photovoltaic response, space-charge-limited current transport, atomic force microscopy, grazing incidence wide-angle X-ray scattering, and density functional theory-level quantum chemical analysis. The data reveal that ITN-C9 and ITzN-C9 organize such that the lowest unoccupied molecular orbital-rich end groups have intermolecular π−π distances as close as 3.31(1) Å, with electronic coupling integrals as large as 38 meV, and internal reorganization energies as small as 0.133 eV, comparable to or superior to those in fullerenes. ITN-C9 and ITzN-C9 have broad solar-relevant optical absorption, and, when blended with PBDB-TF, afford devices with power conversion efficiencies near 10%. Performance differences between ITN-C9 and ITzN-C9 are understandable in terms of molecular and electronic structure distinctions via the influences on molecular packing and orientation with respect to the electrode.

Can boron form coordination complexes with diffuse electrons? Evidence for linked solvated electron precursors

2022 ◽  
Author(s):  
Zachary Jordan ◽  
Shahriar N. Khan ◽  
Benjamin A. Jackson ◽  
Evangelos Miliordos
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Molecular System ◽  
Hydrocarbon Chain ◽  
Solvated Electron ◽  
Excitation Energies ◽  
Functional Theory ◽  
Boron Complexes ◽  
The Stability ◽  
First Time

Abstract Density functional theory and ab initio multi-reference calculations are performed to examine the stability and electronic structure of boron complexes that host diffuse electrons in their periphery. Such complexes (solvated electron precursors or SEPs) have been experimentally identified and studied theoretically for several s- and d-block metals. For the first time, we demonstrate that a p-block metalloid element can form a stable SEP when appropriate ligands are chosen. We show that three ammonia and one methyl ligands can displace two of the three boron valence electrons to a peripheral 1s-type orbital. The shell model for these outer electrons is identical to previous SEP systems (1s, 1p, 1d, 2s). Further, we preformed the first examination of a molecular system consisting of two SEPs bridged by a hydrocarbon chain. The electronic structure of these dimers is very similar to that of traditional diatomic molecules forming bonding and anti-bonding σ and π orbitals. Their ground state electronic structure resembles that of two He atoms, and our results indicate that the excitation energies are nearly independent of the chain length for four carbon atoms or longer. These findings pave the way for the development of novel materials similar to expanded metals and electrides.

A STUDY ON STRAIN AFFECTING ELECTRONIC STRUCTURE OF WURTZITE ZnO BY FIRST PRINCIPLES

2009 ◽  
Vol 23 (19) ◽  
pp. 2339-2352 ◽  
Author(s):  
LI BIN SHI ◽  
SHUANG CHENG ◽  
RONG BING LI ◽  
LI KANG ◽  
JIAN WEI JIN ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Band Structure ◽  
Valence Band ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Electron Density Difference ◽  
Different Strains

Density of states and band structure of wurtzite ZnO are calculated by the CASTEP program based on density functional theory and plane-wave pseudopotential method. The calculations are carried out in axial and unaxial strains, respectively. The results of density of states in different strains show that the bottom of the conduction band is always dominated by Zn 4s, and the top of valence band is always dominated by O 2p. The variation of the band gap calculated from band structure is also discussed. In addition, p-d repulsion is used in investigating the variation of the top of the valence band in different strains and the results can be verified by electron density difference.

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