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Device Characteristics of Bandgap Tailored 10.04% Efficient CZTSSe Solar Cells Sprayed from Water Based Solution
摘要： Diverse S/(S+Se) ratio of Cu2ZnSn(Sx,Se1–x)4 (CZTSSe) thin film solar cells fabricated by water based spray pyrolysis approach. By fine tuning the S/(S+Se) ratio, base CZTSSe device efficiency has significantly improved from 7.02% to 10.04% by minimizing the Voc deficit up to 616 mV and increasing FF from 56.42% to 62.38%. As S/(S+Se) ratio was increased from 0 to 0.4, surface compactness was observed to be improved with slightly decreased grain size, which increased shunt resistance and resultantly increased fill factor. However, S-alloying more than S/(S+Se)=0.4, grain size was too much decreased and had detrimental effect on device performance. To deeply understand the role effect of S/(S+Se) ratio, detailed spectroscopic analysis performed with admittance spectroscopy (AS), temperature dependent current-voltage characteristic (J-V-T), time-resolved photoluminescence (TRPL) and Raman depth profiling. Experimental results revealed that the different power conversion efficiency (PCE) limiting factors were developed with various S/(S+Se) ratio. High density of deep defect states generated with S/(S+Se) ≥ 40% content and larger conduction band offset observed with red kink were formed in the Se/(S+Se) ≥ 80% content. Hence, in order to get high efficient CZTSSe solar cell, fine tuning of S/(S+Se) ratio is necessary.
关键词： Aqueous solution,Defect characterization,Spray deposition,Chalcogen ratio,Photovoltaic properties,CZTSSe thin films
更新于2025-09-12 10:27:22
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The role of traps in the photocurrent generation mechanism in thin InSe photodetectors
摘要： Due to the excellent electrical transport properties and optoelectronic performance, thin indium selenide (InSe) has recently attracted attention in the field of 2D semiconducting materials. However, the mechanism behind the photocurrent generation in thin InSe photodetectors remains elusive. Here, we present a set of experiments aimed at explaining the strong scattering in the photoresponsivity values reported in the literature for thin InSe photodetectors. By performing optoelectronic measurements on thin InSe-based photodetectors operated under different environmental conditions we find that the photoresponsivity, the response time and the photocurrent power dependency are strongly correlated in this material. This observation indicates that the photogating effect plays an important role for thin InSe flakes, and it is the dominant mechanism in the ultra-high photoresponsivity of pristine InSe devices. In addition, when exposing the pristine InSe photodetectors to the ambient environment we observe a fast and irreversible change in the photoresponse, with a decrease in the photoresponsivity accompanied by an increase of the operating speed. We attribute this photodetector performance change (upon atmospheric exposure) to the decrease in the density of the traps present in InSe, due to the passivation of selenium vacancies by atmospheric oxygen species. This passivation is accompanied by a downward shift of the InSe Fermi level and by a decrease of the Fermi level pinning, which leads to an increase of the Schottky barrier between Au and InSe. Our study reveals the important role of traps induced by defects in tailoring the properties of devices based on 2D materials and offers a controllable route to design and functionalize thin InSe photodetectors to realize devices with either ultrahigh photoresposivity or fast operation speed.
关键词： photogating,chalcogen vacancy,2D material,photocurrent generation,InSe,traps
更新于2025-09-11 14:15:04
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Chalcogen‐Fused Perylene Diimides‐Based Non‐Fullerene Acceptors for High Performance Organic Solar Cells: Insight into the Effect of O, S and Se
摘要： Three perylene diimide tetramers annulated by oxygen (O), sulfur (S) and selenium (Se), named as SF-4PDI-O, SF-4PDI-S and SF-4PDI-Se, are designed, synthesized and paired with polymeric donor PDBT-T1 to construct OSCs. The heteroatoms’ effect on photoelectric properties, chemical geometry, charge transport, active-layer morphology, and photovoltaic performance are investigated in detail. These PDI acceptors exhibit similar absorption profile; while HOMOs and LUMOs are simultaneously upshifted when heteroatoms are altered from O, S to Se due to the gradually weakening electronegativity. Alongside PDBT-T1, SF-4PDI-O achieved the outstanding PCE of 8.904% with a high FF of 0.706, outcompeting its S-annulated and Se-annulated counterparts. The superiority of PDBT-T1: SF-4PDI-O system lies in stronger crystallinity, more balanced hole and electron mobilities, weaker bimolecular recombination, coupled with more efficient charge transfer and collection. These results shed light on the invention of high-performance PDI acceptors by oxygen-decorated methodology.
关键词： chalcogen,nonfullerene,organic solar cells,perylene diimides,small molecule acceptors
更新于2025-09-11 14:15:04
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The effect of chalcogen and metal on the electronic properties and stability of metal–chalcogenides clusters, TM6Xn(PH3)6 (TM = Mo, Cr, Re, Co, Ni; X = Se, Te; n = 8,5)
摘要： We have performed a comparative study of the electronic structure, stability, and magnetic properties of a series of metal–chalcogen clusters stabilized by PH3 ligands. Clusters studied include TM6X8(PH3)6, TM = Cr, Mo, Re, Co, X = Se, Te, and Ni6X(PH3)6, X = Se, and Te. We find that the phosphine ligands act as charge donors, transferring charge to the metal sites, creating an electrostatic effect that lowers the ionization energy. The electronic structure of the cluster also has a significant effect on its charge donor properties, as the Re cluster has a closed electronic shell with a charge state of +2, making it an alkaline earth superatom. The chromium clusters are found to have a series of close lying magnetic isomers. Selenium is a better charge acceptor than tellurium and this causes the telluride clusters to have lower ionization potentials, while the enhanced charge transfer to selenium increases the binding energy of the phosphine ligand.
关键词： metal–chalcogen clusters,PH3 ligands,ionization energy,superatom,stability,charge transfer,magnetic properties,electronic structure
更新于2025-09-10 09:29:36
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Effect of excess electron on structure, bonding, and spectral properties of sulfur/selenium based dichalcogen systems
摘要： First principle based quantum chemical methods are employed to characterize structure, bonding, and spectral properties of sulfur and selenium based dichalcogen systems in presence of an excess electron. Inter molecular two-center three-electron (2c-3e) bonding between two chalcogen (X) atoms is described in the systems of the type (R-X)2?- (R = Ph, PhCH2 X = S, Se). In addition, effect of electron withdrawing (-NO2) and electron donating (-CH3) groups in phenyl ring on the stability of these 2c-3e bonded systems is also studied in water medium applying a macroscopic hydration model. Molecular parameters and binding energy of the neutral, (R-X)2 and reduced, (R-X)2?- dichalcogen systems are compared. Search for minimum energy structures of these open shell doublet systems are carried out applying various density functionals with dispersion corrections and MP2 method considering 6-311++G (d,p) set of basis functions for all atoms. Effect of water medium is introduced through a macroscopic solvation model based on density (SMD). Frontier molecular orbitals based analysis is carried out for showing the definite presence of 2c-3e bond between two chalcogen atoms in these radical anions of sulfur and selenium based aromatic dichalcogen systems. Excited state calculations are performed on all these systems using Time Dependent Density Functional Theory (TDDFT). UV-Vis spectra are simulated and effect of solvent water on the absorption maximum of these radical anions is discussed. This study illustrates that the combination of electronic effect and geometrical flexibility decides the strength of two-center three-electron bond in these systems.
关键词： sulfur,hemi bond,radical anion,density functional theory,chalcogen,excess electron,2c-3e bond,antioxidant,selenium
更新于2025-09-04 15:30:14