Lead-free Magnetic Double Perovskites for Photovoltaic and Photocatalysis Applications

The magnetic spin degrees of freedom in magnetic materials serve as additional capability to tune materials properties, thereby invoking magneto-optical response. Herein, we report the magneto-optoelectronic properties of a family of lead-free magnetic double perovskites Cs_{2}AgTX_{6} (T = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu; X=Cl, Br, I). This turns out to provide an extremely fertile series, giving rise to potential candidate materials for photovoltaic(PV) applications. In conjunction with high absorption coefficient and high simulated power conversion efficiency for PV applications, few compounds in this series exhibit novel magnetic character useful for spintronic applications. The interaction between magnetism and light can have far-reaching results on the photovoltaic properties as a consequence of the shift in the defect energy levels due to Zeeman effect. This subsequently affects the recombination rate of minority carriers, and hence the photoconversion efficiency. Moreover, the distinct ferromagnetic and anti-ferromagnetic ordering driven by hybridization and super-exchange mechanism can play a significant role to break the time-reversal and/or inversion symmetry. Such a coalescence of magnetism and efficient optoelectronic response has the potential to trigger magnetic/spin anomalous photovoltaic (non-linear Optical) effect in this Cs$_{2}$AgTX$_{6}$ family. These insights can thus channelize the advancement of lead-free double perovskites in magnetic/spin anomalous photovoltaic field as well.Comment: 9 pages, 5 figures, 1 tabl

Mixed-halide vacancy-ordered double perovskite for photovoltaic and photocatalysis applications

Here, we report detailed first-principles calculations of the structural stability, optoelectronic properties, and interaction with water for a wide range of mixed-halide compositions of vacancy-ordered double perovskites Cs2Pt(ClxI1-x)6. Our calculations reveal that lower halide dopant levels subdue phase segregation and enhance the stability. Cs2Pt(ClxI1-x)6 demonstrate improved defect tolerance as compared to Cs2PtI6 due to the covalent nature of the Pt - X bond. The chloride-rich Cs2Pt(ClxI1-x)6 exhibit notably improved stability against reaction with water, far surpassing Cs2PtI6 due to the enhanced Cs - Cl bond strength and lower charge transfer between adsorbed H2O and surface Cs atoms. The spectroscopic limited maximum photovoltaic efficiency for the optimal composition of Cs2Pt(Cl0.04I0.96)6 under 1 sun AM1.5G is determined to be 24% for a 5-μm-thick film. Our calculations also suggest that the valence-band edge of this material might be positioned more positive than the standard potential of the oxygen-evolution reaction. These two factors combined with the high stability against reaction with water indicate that Cs2Pt(Cl0.04I0.96)6 might be of considerable interest as a photovoltaic absorber, and possibly as a component of anodes for the photoelectrocatalytic water oxidation. Meanwhile, Cs2Pt(Cl0.96I0.04)6 traverses relevant reduction and oxidation redox potentials, affirming it as a promising candidate for the overall photo(electro)catalyst water-splitting reaction.</p

HaHc (Hydroxylamine Hydrochloride) Assisted Dual Surface Passivation via Charge Neutralization and Coordination Bond Formation of Cs₂AgBiBr₆ Double Perovskite for Solar Cell Application

The growth of lead-free perovskite-based solar cells is the key to achieve sustainable and green energy. Cs2AgBiBr6 (CABB) is one of the lead-free perovskites that is showing appreciable improvement in terms of performance of solar cells. The performance is still limited due to the presence of surface defects on the perovskite surface. In this work, by the use of hydroxylamine hydrochloride (HaHc) additive, the power conversion efficiency (PCE) of the device is able to get a boost of 167% to reach almost 2% PCE because of successful defect passivation of the perovskite surface. Also, the density functional theory (DFT) analysis reveals the successful lowering of energy at the perovskite surface via charge neutralization and the formation of coordination bonds. The device is capable of being fabricated in wet conditions (70% RH) and has excellent storing stability while retaining 80% of its initial PCE for more than 25 days.</p