Solvent-Mediated Intragranular-Coarsening of CH₃NH₃PbI₃ Thin Films toward High-Performance Perovskite Photovoltaics

The deposition of dense and uniform perovskite films with large grains is crucial for fabricating high-performance perovskite solar cells (PSCs). High-quality CH₃NH₃PbI₃ films were produced by a self-induced intragranular-coarsening approach. The perovskite precursor solution contained a Lewis base, <i>N</i>,<i>N</i>-dimethyl sulfoxide (DMSO), and was deposited using a gas-assisted, one-step, spin-coating method that was followed by a solvent vapor-assisted annealing treatment using a mix of DMSO and chlorobenzene (CBZ). Combining solvent-engineering with gas-assisted deposition helps to form intermediate crystalline entities upon evaporation of the parent solvent but retards the otherwise fast reaction between the precursor ingredients. Subsequent cosolvent annealing induces further grain-coarsening via a facilitated dissolution–precipitation process. This technique produced flat CH₃NH₃PbI₃ films featuring large grain microstructures, with well-coarsened subgrains and a reduction of intragranular defects that minimized carrier recombination. The optimized CH₃NH₃PbI₃ films exhibited enhanced crystallinity, excellent carrier transport and injection, as well as suppressed charge recombination. Benefiting from these advantages, PSCs based on the optimized perovskite films delivered a power conversion efficiency of 17.99% and a stabilized power output above 17.30%. This study presents an effective strategy for the fabrication of high-quality, hybrid perovskite films with potential applications in optoelectronic devices

Rational Surface Engineering of Anatase Titania Core–Shell Nanowire Arrays: Full-Solution Processed Synthesis and Remarkable Photovoltaic Performance

The high-performance of a well-aligned 1D nanostructured electrode relies largely on a smart and rational modification with other active nanomaterials. Herein, we present a facile solution-based route to fabricate a well-aligned metal oxide-based core–shell hybrid arrays on TCO substrate. Demonstrated samples included nanowire@nanoparticle (TNW@NP) or nanowire@nanosheet (TNW@NS) with a unique porous core/shell nanowire arrays architecture in the absence or presence of DETA during the solvothermal treatment process. The “alcoholysis” and “ripening” growth mechanism is proposed to explain the formation of honeycomb-like nanosheets shell on nanowires core. Based on careful control of experimental condition, a novel double layered TiO₂ photoanode (DL-TNW@NS-YSHTSs) consisting of 16 μm thick TNW@NS under layer and 6 μm thick yolk–shell hierarchical TiO₂ microspheres (YSHTSs) top layer can be obtained, exhibiting an impressive PCE over 10% at 100 mW cm^–2, which can be attributed to the well-organized photoanode composed of hierarchical core–shell arrays architecture and yolk–shell hollow spheres architecture with synergistic effects of high dye loading and superior light scattering for prominent light harvesting efficiency

Multistack Integration of Three-Dimensional Hyperbranched Anatase Titania Architectures for High-Efficiency Dye-Sensitized Solar Cells

An unprecedented attempt was conducted on suitably functionalized integration of three-dimensional hyperbranched titania architectures for efficient multistack photoanode, constructed via layer-by-layer assembly of hyperbranched hierarchical tree-like titania nanowires (underlayer), branched hierarchical rambutan-like titania hollow submicrometer-sized spheres (intermediate layer), and hyperbranched hierarchical urchin-like titania micrometer-sized spheres (top layer). Owing to favorable charge-collection, superior light harvesting efficiency and extended electron lifetime, the multilayered TiO₂-based devices showed greater <i>J</i>_sc and <i>V</i>_oc than those of a conventional TiO₂ nanoparticle (TNP), and an overall power conversion efficiency of 11.01% (<i>J</i>_sc = 18.53 mA cm^–2; <i>V</i>_oc = 827 mV and FF = 0.72) was attained, which remarkably outperformed that of a TNP-based reference cell (η = 7.62%) with a similar film thickness. Meanwhile, the facile and operable film-fabricating technique (hydrothermal and drop-casting) provides a promising scheme and great simplicity for high performance/cost ratio photovoltaic device processability in a sustainable way

Trilayered Photoanode of TiO₂ Nanoparticles on a 1D–3D Nanostructured TiO₂‑Grown Flexible Ti Substrate for High-Efficiency (9.1%) Dye-Sensitized Solar Cells with Unprecedentedly High Photocurrent Density

An engineered and optimized trilayered TiO₂ photoelectrode on Ti metal substrates with synergistic effects for dye-sensitized solar cells has been developed through the combination of one-dimensional (1D) TiO₂ nanotubes, three-dimensional (3D) TiO₂ hierarchical microsized spheres, as well as zero-dimensional (0D) nanoparticles with a large surface area. The advantages of efficient charge-collection, light-harvesting, as well as high dye-loading capability make it possible to achieve unprecedentedly high short-circuit photocurrent density (17.90 mA cm^–2) under back-side illumination and thus allow us to obtain a power conversion efficiency as high as 9.10%