Kacper Cichy

This paper proposes molecular and supramolecular concepts for potential application in perovskite solar cells. New air-stable symmetrical imine, with thiadiazole moieties PPL2: (5E,6E)-N2,N5-bis(4-(diphenylamino)benzylidene)-1,3,4-thiadiazole-2,5-diamine), as a hole-transporting material was synthesised in a single-step reaction, starting with commercially available and relatively inexpensive reagents, resulting in a reduction in the cost of the final product compared to Spiro-OMeTAD. Moreover, camphorsulfonic acid (CSA) in both enantiomeric forms was used to change the HOMO-LUMO levels and electric properties of the investigated imine-forming complexes. Electric, optical, thermal, and structural studies of the imine and its complexes with CSA were carried out to characterise the new material. Imine and imine/CSA complexes were also characterised in depth by the proton Nuclear Magnetic Resonance ¹H NMR method. The position of nitrogen in the thidiazole ring influences the basicity of donor centres, which results in protonation in the imine bond. Simple devices of ITO/imine (with or without CSA(−) or CSA(+))/Ag/ITO architecture were constructed, and a thermographic camera was used to find the defects in the created devices. Electric behaviour was also studied to demonstrate conductivity properties under the forward current. Finally, the electrical properties of imine and its protonated form with CSA were compared with Spiro-OMeTAD. In general, the analysis of thermal images showed a very similar response of the samples to the applied potential in terms of the homogeneity of the formed organic layer. The TGA analysis showed that the investigated imine exhibits good thermal stability in air and argon atmospheres.

The A-site cation-ordered GdBa_0.5Sr_0.5Co_2-xCu_xO_5+δ (GBSCC) double perovskites are evaluated regarding the development of high-performance oxygen electrodes for reversible solid oxide cells (rSOCs). The aims are to maximally decrease the content of toxic and expensive cobalt by substitution with copper while at the same time improving or maintaining the required thermomechanical and electrocatalytic properties. Studies reveal that compositions with 1 ≤ x ≤ 1.15 are particularly interesting. Their thermal and chemical expansions are decreased, and sufficient transport properties are observed. Complementary density functional theory calculations give deeper insight into oxygen defect formation in the considered materials. Chemical compatibility with La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) and Ce_0.9Gd_0.1O_2-δ (GDC) solid electrolytes is evaluated. It is documented that the GdBa_0.5Sr_0.5Co_0.9Cu_1.1O_5+δ oxygen electrode enables obtaining very low electrode polarization resistance (R_p) values of 0.017 Ω cm² at 850 °C as well as 0.111 Ω cm² at 700 °C, which is lower in comparison to that of GdBa_0.5Sr_0.5CoCuO_5+δ (respectively, 0.026 and 0.204 Ω cm²). Systematic distribution of relaxation times analyses allows studies of the electrocatalytic activity and distinguishing elementary steps of the electrochemical reaction at different temperatures. The rate-limiting process is found to be oxygen atom reduction, while the charge transfer at the electrode/electrolyte interface is significantly better with LSGM. The studies also allow elaborating on the catalytic role of the Ag current collector as compared with Pt. The electrodes manufactured using materials with x = 1 and 1.1 permit reaching high power outputs, exceeding 1240 mW cm^-2 at 850 °C and 1060 mW cm^-2 at 800 °C, for the LSGM-supported cells, which can also work in the electrolysis mode.

The studies of structural, thermogravimetric, and charge transport properties of the BaZr_1/8Hf_1/8Sn_1/8Ti_1/8y_1/8In_1/8Sm_1/8Yb_1/8O_3-x oxide were performed with XRD, HT-XRD, TGA, impedance spectroscopy and electrical conductivity relaxation (ECR). It was found that the incorporation of water into BaZr_1/8Hf_1/8Sn_1/8Ti_1/8y_1/8In_1/8Sm_1/8Yb_1/8O_3-x leads to the chemical expansion of the unit cell. The temperature range of water sorption and desorption from the structure as well as the amount of incorporated water were determined. The electrical properties of the sample were investigated by electrochemical impedance spectroscopy in dry, H₂O- and D₂O-containing synthetic air in the 300-800 °C temperature range, which enabled the evaluation of the protonic and deuterium conductivity along with their transport numbers. Based on the bulk and grain boundary conductivity, the potential at a grain boundary φ₀ as well as the Debye length L_D and space charge layer (SCL) thickness λ for protonic and deuteronic defects were calculated. For the first time in the case of high entropy material, the relaxation kinetics of the electrical conductivity studies were performed. The ECR observed in the 300-600 °C temperature range revealed a single-fold nature, which indicates a negligible component of the electronic hole conductivity in the hydrated material. The gathered data allowed the calculation of the chemical diffusion coefficient of water DH₂O and the chemical surface exchange coefficient of water kH₂O along with their activation energies. The chemical diffusion coefficient DH₂O is in a range of 10^-8 -10^-6cm² s^-1, and the chemical surface exchange coefficient kH₂O in a range of 10^-6 -10^-4cm s^-1.

It has been documented that the total electrical conductivity of the hexagonal rare-earth manganites Y_0.95Pr_0.05MnO_3+δ and Y_0.95Nd_0.05MnO_3+δ, as well as the undoped YMnO_3+δ, is largely dependent on the oxygen excess δ, which increases considerably at temperatures below ca. 300 °C in air or O₂. Improvement for samples maintaining the same P6₃cm crystal structure can exceed 3 orders of magnitude below 200 °C and is related to the amount of the intercalated oxygen. At the same time, doping with Nd³⁺ or Pr³⁺ affects the ability of the materials to incorporate O₂, and therefore indirectly influences the conductivity as well. At high temperatures (700–1000 °C) and in different atmospheres of Ar, air, and O₂, all materials are nearly oxygen-stoichiometric, showing very similar total conduction with the activation energy values of 0.8–0.9 eV. At low temperatures in Ar (δ ≈ 0), the mean ionic radius of Y_1−xLn_x appears to influence the electrical conductivity, with the highest values observed for the parent YMnO₃. For Y_0.95Pr_0.05MnO_3+δ oxide, showing the largest oxygen content changes, the recorded dependence of the Seebeck coefficient on the temperature in different atmospheres exhibits complex behavior, reflecting oxygen content variations, and change of the dominant charge carriers at elevated temperatures in Ar (from electronic holes to electrons). Supplementary cathodic polarization resistance studies of the Y_0.95Pr_0.05MnO_3+δ electrode document different behavior at higher and lower temperatures in air, corresponding to the total conduction characteristics.

Nd₂CuO[Formula: see text] is known to possess either oxygen vacancies or interstitial oxygen defects, depending on the synthesis route, as well as may exhibit the A-site deficiency. In this work, insight into physicochemical properties of Nd₂CuO[Formula: see text] and Nd[Formula: see text]CuO[Formula: see text] layered oxides is given, focusing on the crystal structure, electrical conductivity, and oxygen permeation, as well as on numerical density functional theory (DFT) simulations concerning ionic defects formation and their possible movement in the crystal structure. The results indicate that in oxidizing conditions at low temperatures, interstitial oxygen defects are stable, but with the increase of temperature, the release of oxygen is observed, leading to formation of the oxygen vacancies. Both materials are stable at elevated temperatures in air and Ar. Larger oxygen nonstoichiometry and improved electrical conductivity at high temperatures for Nd[Formula: see text]CuO[Formula: see text] compound are accompanied by the recorded oxygen flux of ca. 0.2[Formula: see text]mL[Formula: see text]cm[Formula: see text][Formula: see text]min[Formula: see text] at 880^∘C for 0.8[Formula: see text]mm thick ceramic membrane.

Planar perovskite solar cells were fabricated on F-doped SnO₂ (FTO) coated glass substrates, with 4,4’-((1E,1’E)-((1,2,4-thiadiazole-3,5-diyl)bis(azaneylylidene))bis(methaneylylidene))bis(N,N-di-p-tolylaniline) (bTAThDaz) as hole transport material. This imine was synthesized in one step reaction, starting from commercially available and relatively inexpensive reagents. Electrochemical, optical, electrical, thermal and structural studies including thermal images and current-voltage measurements of the full solar cell devices characterize the imine in details. HOMO-LUMO of bTAThDaz were investigated by cyclic voltammetry (CV) and energy-resolved electrochemical impedance spectroscopy (ER-EIS) and were found at −5.19 eV and −2.52 eV (CV) and at −5.5 eV and −2.3 eV (ER-EIS). The imine exhibited 5% weight loss at 156 °C. The electrical behavior and photovoltaic performance of the perovskite solar cell was examined for FTO/TiO₂/perovskite/bTAThDaz/Ag device architecture. Constructed devices exhibited good time and air stability together with quite small effect of hysteresis. The observed solar conversion efficiency was 14.4%.

The oxygen storage capacity, oxygen exchange kinetics, structure and thermodynamic stability were studied for hexagonal Y_0.7Tb_0.3MnO_3+δ in oxygen and air to assess its applicability for oxygen separation from air by a temperature-swing adsorption process.