Hybrid Al2O3-CH3NH3PbI3 Perovskites towards Avoiding Toxic Solvents

Low-Temperature Processed Brookite Interfacial Modification for Perovskite Solar Cells with Improved Performance

The scaffold layer plays an important role in transporting electrons and preventing carrier recombination in mesoporous perovskite solar cells (PSCs), so the engineering of the interface between the scaffold layer and the light absorption layer has attracted widespread concern. In this work, vertically grown TiO₂ nanorods (NRs) as scaffold layers are fabricated and further treated with TiCl₄ aqueous solution. It can be found that a thin brookite TiO₂ nanoparticle (NP) layer is formed by the chemical bath deposition (CBD) method on the surface of every rutile NR with a low annealing temperature (150 °C), which is beneficial for the infiltration and growth of perovskite. The PSC based on the TiO₂ NR/brookite NP structure shows the best power conversion of 15.2%, which is 56.37% higher than that of the PSC based on bare NRs (9.72%). This complex structure presents an improved pore filling fraction and better carrier transport capability with less trap-assisted carrier recombination. In addition, low-annealing-temperature-formed brookite NPs possess a more suitable edge potential for electrons to transport from the perovskite layer to the electron collection layer when compared with high-annealing-temperature-formed anatase NPs. The brookite phase TiO₂ fabricated at a low temperature presents great potential for flexible PSCs.

Perovskite-based solar cells fabricated from TiO2 nanoparticles hybridized with biomaterials from mollusc and diatoms

Perovskite solar cells (PVSCs) convert solar energy into electrical energy. Current study employs fabrication of PVSCs using calcium titanate (CaTiO₃) prepared by co-precipitation of TiO₂ nanoparticle (NP) and CaCO₃ NP with later synthesized from mollusc shell. Furthermore, frustules of diatom, Nitzschia palea were used to prepare silica doped CaTiO₃ (Si-CaTiO₃) nanocomposite. CaTiO₃ NP and Si-CaTiO₃ nanocomposites film were made on fluorine doped tin oxide (FTO) glass plate using spin coater separately for two different kinds of PVSCs tested at different intensities of light. The perovskite materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX) spectroscopy. Thickness of the film was measured by profilometer. The maximum power density (PD_max) of CaTiO₃ made PVSCs was 0.235 mW/m² under white LED light and 0.041 mW/m² in broad spectrum light. Whereas, PD_max of PVSCs with Si-CaTiO₃ was higher about 0.0083 mW/m² in broad spectrum light and was 0.0039 mW/m² in white LED light. This is due to the fact that CaTiO₃ allowed blue and red light in broad spectrum to pass through it without being absorbed compared to white LED light which gets reflected. On the offset, in PVSC made of Si-CaTiO₃ since diatoms frustules are made up of nanoporous architecture it increases the overall porosity of PVSC making them potentially more efficient in broad spectrum of light compared to white LED light.

Metal Oxide Oxidation Catalysts as Scaffolds for Perovskite Solar Cells

Whilst the highest power conversion efficiency (PCE) perovskite solar cell (PSC) devices that have reported to date have been fabricated by high temperature sintering (>500 °C) of mesoporous metal oxide scaffolds, lower temperature processing is desirable for increasing the range of substrates available and also decrease the energy requirements during device manufacture. In this work, titanium dioxide (TiO₂) mesoporous scaffolds have been compared with metal oxide oxidation catalysts: cerium dioxide (CeO₂) and manganese dioxide (MnO₂). For MnO₂, to the best of our knowledge, this is the first time a low energy band gap metal oxide has been used as a scaffold in the PSC devices. Thermal gravimetric analysis (TGA) shows that organic binder removal is completed at temperatures of 350 °C and 275 °C for CeO₂ and MnO₂, respectively. By comparison, the binder removal from TiO₂ pastes requires temperatures >500 °C. CH₃NH₃PbBr₃ PSC devices that were fabricated while using MnO₂ pastes sintered at 550 °C show slightly improved PCE (η = 3.9%) versus mesoporous TiO₂ devices (η = 3.8%) as a result of increased open circuit voltage (V_oc). However, the resultant PSC devices showed no efficiency despite apparently complete binder removal during lower temperature (325 °C) sintering using CeO₂ or MnO₂ pastes.