BiVO4/Cs2PtI6 Vacancy-Ordered Halide Perovskite Heterojunction for Panchromatic Light Harvesting and Enhanced Charge Separation in Photoelectrochemical Water Oxidation

New insight on interfacial charge transfer at graphitic carbon nitride/sodium niobate heterojunction under piezoelectric effect for the generation of reactive oxygen species

Piezocatalytic removal of metronidazole (MET) using graphitic carbon nitride (g-C3N4, GCN)/sodium niobate (NaNbO3) heterojunction was investigated under ultrasonication. Herein, optimized GCN(50)/NaNbO3 heterojunction achieved 87.2% MET removal within 160 min (k = 0.0138 min-1). A new pathway for the generation of reactive oxygen species (ROS) via GCN(50)/NaNbO3 piezocatalytic heterojunction was identified. The type-II heterojunction formulated using optimized GCN(50)/NaNbO3 was found to generate hydroxyl radical (.OH); however, it was thermodynamically not feasible. The main reasons are; (i) piezopotential generated converted type-II to S-scheme heterojunction and resulted in the participation of high oxidizing potential holes in valence band (VB) of NaNbO3, and (ii) formation of depletion region at the GCN-water interface and subsequent improvement in the redox potential of holes, and (iii) piezopotential generated at NaNbO3 provided bias to GCN and established a piezo-electrocatalytic system. The higher screening of piezopotential in presence of external ions was found to reduce the generation of .OH. Overall, self-powered NaNbO3 has great ability to improve interfacial charge transfer at GCN(50)/NaNbO3 to form ROS.

Numerical simulation of lead-free vacancy ordered Cs2PtI6 based perovskite solar cell using SCAPS-1D

In recent years, vacancy-ordered halide double perovskites have emerged as promising non-toxic and stable alternatives for their lead-based counterparts in optoelectronic applications. In particular, vacancy ordered Cs2PtI6 has emerged as a star material because of its high absorption coefficient, band gap of 1.37 eV, and long minority carrier lifetime. Despite substantial experimental research on this new class of material, theoretical simulations of their device properties remain scarce. In this work, a novel n-i-p device architecture (FTO/SnO2/Cs2PtI6/MoO3/C) is theoretically investigated using a solar cell capacitance simulator (SCAPS-1D). Theoretical investigations are carried out in order to optimize the device performance structure by varying the perovskite and selective charge transport layer thickness, absorber and interface defect density, operating temperature, back contact, series and shunt resistance, respectively. The optimized device showed an impressive power conversion efficiency (PCE) of 23.52% at 300 K, which is higher than the previously reported values. Subsequent analysis of the device's spectral response indicated that it possessed 98.9% quantum efficiency (QE) and was visibly active. These findings will provide theoretical guidelines for enhancing the performance of Cs2PtI6-based photovoltaic solar cells (PSCs) and pave the way for the widespread implementation of environmentally benign and stable perovskites.

Solid Electrolyte Interphase Formation in Tellurium Iodide Perovskites during Electrochemistry and Photoelectrochemistry

Halide perovskites are promising photoelectrocatalytic materials. Their further development requires understanding of surface processes during electrochemistry. Thin films of tellurium-based vacancy-ordered perovskites with formula A₂TeI₆, A = Cs, methylammonium (MA), were deposited onto transparent conducting substrates using aerosol-assisted chemical vapor deposition. Thin film stability as electrodes and photoelectrodes was tested in dichloromethane containing tetrabutylammonium PF₆ (TBAPF₆). Using photoemission spectroscopy, we show that the formation of a solid electrolyte interphase on the surface of the Cs₂TeI₆, consisting of CsPF₆, enhances the stability of the electrode and allows extended chopped-light chronoamperometry measurements at up to 1.1 V with a photocurrent density of 16 μA/cm². In contrast, (CH₃NH₃)₂TeI₆ does not form a passivating layer and rapidly degrades upon identical electrochemical treatment. This demonstrates the importance of surface chemistry in halide perovskite electrochemistry and photoelectrocatalysis.