Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

http://science.sciencemag.org/content/sci/345/6196/542.full.pdf

Interface engineering of highly efficient perovskite solar cells

A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized. Fullerene-free polymer solar cells (PSCs) based on the ITIC acceptor are demonstrated to exhibit power conversion effi ciencies of up to 6.8%, a record for fullerene-free PSCs.

An electron acceptor challenging fullerenes for efficient polymer solar cells.

Recent Advances in Bulk Heterojunction Polymer Solar Cells

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Numerical Heat Transfer And Fluid Flow

Perovskite quantum wells yield highly efficient LEDs spanning the visible and near-infrared.

/pdf/perovskite-light-emitting-diodes-based-on-solution-processed-1i56kycdls.pdf

Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

A contactless emulsification method is presented using corona discharge. The corona discharge forms using a pin-to-plate configuration, creating a non-uniform electric field. This results in a simultaneous electrohydrodynamic (EHD) pumping of silicone oil and an electroconvection of water droplets that accelerate and submerge inside the oil, leading to a continuous water-in-oil (W/O) emulsion formation process. The impact of the oil viscosity and corona generating AC and DC electric fields (i.e., voltage and frequency) on the characteristics of the emulsions is studied. The emulsification power consumption using the AC and DC electric fields is calculated and compared to traditional emulsion formation methods. While using the DC electric field results in the formation of uniform emulsions, the AC electric field is readily available and uses less power for the emulsification. This is facile, contactless, and energy-efficient for the continuous formation of W/O emulsions.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.3c01369

Impact of Processing Parameters on Contactless Emulsification via Corona Discharge

Elastomers are the main material component for footwear and tires contact applications. However, they exhibit low traction on wet ice, resulting in slips and falls for individuals and vehicles during wintertime. Textured elastomeric short fiber composites can be manufactured in a scalable manner with conventional processing techniques such as injection molding, and have promising wet ice slip resistance behavior. However, the state-of-the-art textured composite approaches employs one-dimensional (1D) micron-scale fibers that are prone to mechanical abrasion on hard surfaces, resulting in their ice traction decay over time. Here, we demonstrate a novel microstructural design strategy for developing durable slip-resistant composites using nanomaterials. To this aim, a series of micron- and nanoscale 1D and 2D fibers as additives in the textured elastomers are evaluated for surface morphology, ice-traction, and wear-resistance. We show that unlike 1D and other 2D counterparts, hexagonal graphene nanoplatelets (GNP) exhibit superior wear-resistance and an anomalous wear-induced increase in ice-traction functionality. Specifically, the partially agglomerated morphology of the GNP surfaces results in a hierarchical surface texturing, which imparts the surface with a 64% ice traction improvement (0.46 ± 0.11; p < 0.0001) at a low surface weight loss (2.44 mg cm−2). This study provides new microstructural design pathways for designing durable non-slip composites and can shed light on new applications for the diverse class of 2D nanomaterials. 

Nanotextured surfaces with enhanced ice-traction and wear-resistance

Mechanical and physical properties of porous polymers are highly dependent on the arrangement of their internal pores, which once synthesized are widely considered static. However, here we introduce an unconventional dynamic porosity strategy in physically networked elastomer polymers, irrespective of their chemistry. This strategy allows for an omnidirectional and reversible reconfiguration of porosity in response to applied mechanical deformations, even at ambient conditions. In particular, the normal contact pressure between human fingers (just 0.62 MPa) applied on thin elastomer films results in a permanent reversion of the pores to a denser and more solid state. The porous-to-solid transition leads to a 3 order of magnitude reduction in pore density and up to a 22% relative volumetric shrinkage of the films, resulting in an opaque-to-transparent transition (OTT) that acts as a visual indication of porosity state (porous vs nonporous). It is shown that the pore reversion pressure onset is dependent on the average pore-to-pore distance that is controllable through process-specific parameters. Furthermore, the porosity transition is reversible for multiple cycles when the through-plane compression activation is coupled with an in-plane stretch (e = 700%). A strain energy-mediated thermodynamic model is successfully implemented to confirm the effects of mechanical deformations on pore reversion and generation. Finally, applications of the newfound dynamic porosity concept are exploited for pressure indication, on-demand modulation of materials' mechanical and thermal characteristics, and flexible photomasks.

Hossein Sojoudi

Papers

Impact of Processing Parameters on Contactless Emulsification via Corona Discharge

Nanotextured surfaces with enhanced ice-traction and wear-resistance

Universal Strain Energy-Mediated Dynamic Porosity in Physically Networked Elastomers and Their Applications.