1. The role of fluorine-functionalized organic spacers for defect passivation and low-dimensional phase formation in 3D MAPI perovskite solar cellsAli Semerci, Javier Urieta-Mora, Sander Driessen, Ali Buyruk, Rik Hooijer, Agustín Molina-Ontoria, Bülent Alkan, Seckin Akin, Mattia Fanetti, Saim Emin, 2025, izvirni znanstveni članek Opis: Widespread application of organic-inorganic halide perovskites (OIHP) still faces a major obstacle in mitigating moisture-induced degradation. Integrating organic spacers, as defect passivation facilitators along with low-dimensional phase (LDP) formation is an effective approach to enhance the efficiency and robustness of 3D methyl ammonium lead iodide (MAPI) in photovoltaics (PV). Here, the formamidinium cation (FA+) employing 3,5-difluorobenzene-1-carboximidamidium iodide (2F), 4-(trifluoromethyl)benzene-1-carboximidamidium iodide (3F),
and 2,3,4,5,6-pentafluorobenzene-1-carboximidamidium iodide (5F) organic spacers as passivation layer in 3D/LDP OIHP solar cells is utilized. Fluorine atom position and quantity in organic spacers change the optoelectronic characteristics of the perovskites, enhancing hydrophobicity, facilitating LDP formation, and augmenting dipole moments, thereby facilitating charge separation processes. PV performance analysis reveals that 3F-treated 3D/LDP devices achieve the highest efficiency of 19.22%. Experimental results and density functional theory (DFT) studies attribute the higher performance of 3F-modified devices to effective LDP formation, enhanced passivation of defect states at perovskite surfaces and grain boundaries, the highest dipole moment and lowest band gap among the evaluated spacers. The stability tests show that, after 1000 h, 3F- and 5F-modified 3D/LDP OIHP devices retain over 85% of their initial efficiency. This research opens novel avenues for designing appropriate organic spacers to attenuate defects in 3D/LDP PV devices.
Ključne besede: fluorine-functionalized molecules, MAPI perovskite solar cells, deffect passivation
Objavljeno v RUNG: 20.02.2025; Ogledov: 609; Prenosov: 4
 Celotno besedilo (3,26 MB)
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2. Coevaporation of doped inorganic carrier-selective layers for high-performance inverted planar perovskite solar cellsJiexuan Jiang, Andraž Mavrič, Nadiia Pastukhova, Matjaž Valant, Qiugui Zeng, Zeyu Fan, Beibei Zhang, Yanbo Li, 2022, izvirni znanstveni članek Opis: Inorganic carrier selective layers (CSLs), whose conductivity can be effectively tuned by doping, offer low-cost and stable alternatives for their organic counterparts in perovskite solar cells (PSCs). Herein, we employ a dual-source electron-beam co-evaporation method for the controlled deposition of copper-doped nickel oxide (Cu:NiO) and tungsten-doped niobium oxide (W:Nb2O5) as hole and electron transport layers, respectively. The mechanisms for the improved conductivity using dopants are investigated. Owing to the improved conductivity and optimized band alignment of the doped CSLs, the all-inorganic-CSLs-based PSCs achieves a maximum power conversion efficiency (PCE) of 20.47%. Furthermore, a thin titanium buffer layer is inserted between the W:Nb2O5 and the silver electrode to prevent the halide ingression and improve band alignment. This leads to a further improvement of PCE to 21.32% and a long-term stability (1200 h) after encapsulation. Finally, the large-scale applicability of the doped CSLs by co-evaporation is demonstrated for the device with 1 cm2 area showing a PCE of over 19%. Our results demonstrate the potential application of the co-evaporated CSLs with controlled doping in PSCs for commercialization.
Ključne besede: carrier selective layers, Cu-doped nickel oxide, electron-beam evaporation, perovskite solar cells, W-doped niobium oxide
Objavljeno v RUNG: 17.03.2022; Ogledov: 3700; Prenosov: 128
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3. Unusual magnetodielectric effects in La2CuMnO6 induced by a dynamic crossover in dielectric relaxation at TCJasnamol Pezhumkattil Palakkal, Cheriyedath Raj Sankar, Ajeesh Parayancheri Paulose, Matjaž Valant, Artem Badasyan, Manoj Raama Varma, 2018, izvirni znanstveni članek Opis: A series of fixed frequency dielectric measurements shows dielectric relaxation in La2CuMnO6, with a dynamic
(Arrhenius to Arrhenius) crossover at TC. The external magnetic field alters the relaxation parameters in the
vicinity of crossover and induces an unusual trend in the magnetodielectric coupling around TC. A large magnetodielectric
coupling of 55% (at 68 K, 4 kHz) and 61% (at 105 K, 285.8 kHz) under a small magnetic field of
5 kOe is discovered. Presence of ferromagnetic short-range correlations above TC and a sign reversal of magnetoresistance
around TC are observed. Specific heat analysis revealed the presence of ferromagnetic, variable
range hopping active charge localized state. The presence of ferromagnetic short-range correlations and the
influence of a core-grain dominated magnetoresistance on the Maxwell-Wagner interfacial polarization are responsible
for the observed large magnetodielectric effect. Both the magnetic ordering and external magnetic
field control the electric dipole relaxation in the material.
Ključne besede: Double perovskite
Griffiths-like phase
Dielectric
Magnetoresistance
Magnetodielectric
Objavljeno v RUNG: 03.01.2018; Ogledov: 5080; Prenosov: 0
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4. Donor doping of K0.5Na0.5NbO3 ceramics with strontium and its implications to grain size, phase composition and crystal structureJitka Hreščak, Goran Dražić, Marco Deluca, Iztok Arčon, Alojz Kodre, M. Dapiaggi, Tadej Rojac, Barbara Malič, Andreja Benčan, 2017, izvirni znanstveni članek Opis: In this study, the particular effects of A-site donor doping in a lead-free piezoceramic material K0.5Na0.5NbO3 (KNN) doped with Sr2+, i.e., the crystal-structure change, the secondary-phase formation and the grain-size decrease, were investigated. The already-reported causes of these effects upon doping KNN were critically discussed and a mechanism of the effects’ formation was suggested and experimentally supported with advanced analytical methods. Extended X-ray absorption fine structure (EXAFS) analyses proved that the Sr occupies the perovskite A-sublattice, and locally modifies the KNN monoclinic structure to cubic. With the help of Sr K-edge EXAFS and wavelength-dispersive X-ray spectroscopy, the Sr was found to be homogenously distributed in the KNN perovskite lattice with 0.5, 1 and 2% Sr and no Sr segregation on the nano level was found in any of the studied samples with transmission electron microscopy. Introducing Sr into the A-sublattice, as well as accounting for the charge-compensating A-site vacancies in the starting composition, causes increasing lattice disorder and microstrain, as determined from a Rietveld refinement of the synchrotron X-ray diffraction data. Above 2% Sr the system segregates the A-site vacancies in a secondary phase in order to release the chemical pressure, as revealed by Raman spectroscopy. All these effects result in an increasing number of low-angle grain boundaries that limit the grain growth and finally lead to a significant grain-size decrease.
Ključne besede: perovskite, potassium sodium niobate, donor doping, cation vacancies
Objavljeno v RUNG: 17.01.2017; Ogledov: 6205; Prenosov: 331
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