Boosted performances of mesoscopic perovskite solar cells using LaFeO3 inorganic perovskite nanomaterial

Rational modification of TiO2 photoelectrodes with spinel ZnFe2O4 and Ag-doped ZnFe2O4 nanostructures highly enhanced the efficiencies of dye sensitized solar cells

To develop effective photoelectrode nanomaterials for dye-sensitized solar cells (DSSCs), spinel ZnFe₂O₄ (2.5, 5, 7.5, 10 wt%) and Ag-doped ZnFe₂O₄ (Ag_xZn_1-x/2Fe₂O₄, x = 0.1, 0.2, 0.3, 0.4 mmol) nanomaterials were added into the TiO₂ photoanodes. It was found that the DSSC fabricated with TiO₂ + 5 wt% ZnFe₂O₄ exhibited the most improved efficiency of 3.89 % among the ZnFe₂O₄ containing devices. Furthermore, the power conversion efficiency (PCE) values were boosted when the Ag⁺ cations were doped into the ZnFe₂O₄ crystalline lattice. The greatest PCE = 5.75 % was achieved for the solar cell assembled using TiO₂ + 5 wt% Ag_0.2Zn_0.90Fe₂O₄ photoanode indicating 47.81 % improved performance relative to that of the reference DSSC containing TiO₂ + 5 wt% ZnFe₂O₄ photoelectrode. The electrochemical impedance spectra (EIS) approved that the DSSC with the TiO₂ + 5 wt% Ag_0.2Zn_0.90Fe₂O₄ photoelectrode nanomaterial had the lowest charge transfer resistance but the greatest e-h recombination resistance at the interfaces of photoanode/dye/electrolyte. Hence, it had the quickest electron transport rate, and the greatest electron collecting efficiency in addition to the highest dye loading capacity and least photoluminescence (PL) intensity (charge recombination) which were all prominently beneficial for improvement of the DSSC performance.

Efficient hole transport materials based on naphthyridine core designed for application in perovskite solar photovoltaics

Naphthyridine-based compounds with a donor-acceptor-donor (D-A-D) skeleton were considered as hole transport materials (HTMs) for perovskite solar cells (PSCs). The optical characteristics, stability, solubility, Hirshfeld surface analysis, crystal structure, and hole transport properties of the HTMs were studied systematically. The HOMO energies of all HTMs were higher than valence band of CH₃NH₃PbI₃ (MAPbI₃) perovskite signifying naphthyridine-based HTMs had appropriate energy alignments for usage in PSCs. The LUMO level of designed HTMs were higher than MAPbI₃ conduction band ensuring prevention of backward electronic movement from MAPbI₃ to the cathode. The λ_abs^max amounts of all HTMs were close 400 nm, which showed their competition with perovskite was impossible. The 18NP and 26NP HTMs had higher hole mobilities compared to that of the Spiro-OMeTAD. Considering aligned HOMO energies, suitable hole mobilities, satisfactory stability and solubility, 18NP (1,8-Naphthyridine) and 26NP (2,6-Naphthyridine) were introduced as the best HTM materials for PSCs which could replace Spiro-OMeTAD.

Molecular engineering of several butterfly-shaped hole transport materials containing dibenzo[b,d]thiophene core for perovskite photovoltaics

Several butterfly-shaped materials composed of dibenzo[b,d]thiophene (DBT) and dibenzo-dithiophene (DBT5) cores were designed as hole transporting materials (HTMs) and their properties were studied by density functional theory (DFT) computations for usage in mesoscopic n-i-p perovskite solar cells (PSCs). To choose suitable HTMs, it was displayed that both of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energies of molecules were located higher than those of CH₃NH₃PbI₃ (MAPbI₃) perovskite as they were able to transfer holes from the MAPbI₃ toward Ag cathode. Negative solvation energy (ΔE_solvation) values for all HTMs (within the range of - 5.185 to - 18.140 kcal/mol) revealed their high solubility and stability within CH₂Cl₂ solvent. The DBT5-COMe demonstrated the lowest values of band gap (E_g = 3.544) and hardness (η = 1.772 eV) (the greatest chemical activity) and DBT5-CF₃ displayed the biggest η = 1.953 eV (maximum stability) that were predominantly valuable for effective HTMs. All HTMs presented appropriately high LHEs from 0.8793 to 0.9406. In addition, the DBT5 and DBT5-SH depicted the lowest exciton binding energy (E_b) values of 0.881 and 0.880 eV which confirmed they could produce satisfactory results for the PSCs assembled using these materials. The DBT5-SH and DBT5-H had maximum hole mobility (μ_h) values of 6.031 × 10^-2 and 1.140 × 10^-2 which were greater than those measured for the reference DBT5 molecule (μ_h = 3.984 × 10^-4 cm²/V/s) and about 10 and 100 times superior to the calculated and experimental μ_h values for well-known Spiro-OMeTAD. The DBT5-COOH illustrated the biggest open circuit voltage (V_OC), fill factor (FF) and power conversion efficiency (PCE) values of 1.166 eV, 0.896 and 23.707%, respectively, establishing it could be as the best HTM candidate for high performance PSCs.