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

Thin films of bilayer poly(divinyl benzene) p(DVB)/poly(perfluorodecylacrylate) (p-PFDA) are synthesized via iCVD on steel and silicon substrates. Nanomechanical measurements reveal that the elastic modulus and hardness of the films are enhanced through the bilayer structure and that the adhesion of the films to the substrate is improved via in situ grafting mechanism. The strength of ice adhesion to the treated surfaces is reduced more than six-fold when the substrates are coated with these bilayer polymer networks.

/pdf/linker-free-grafting-of-fluorinated-polymeric-cross-linked-1wjcy41eas.pdf

Linker-free grafting of fluorinated polymeric cross-linked network bilayers for durable reduction of ice adhesion

CVD graphene has been n- and p-doped using redox-active, solution-processed metal–organic complexes. Electrical measurements, photoemission spectroscopies, and Raman spectroscopy were used to characterise the doped films and give insights into the changes. The work function decreased by as much as 1.3 eV with the n-dopant, with contributions from electron transfer and surface dipole, and the conductivity significantly increased.

Production of heavily n- and p-doped CVD graphene with solution-processed redox-active metal–organic species

Chemical vapor deposition (CVD) polymerization uses vapor phase monomeric reactants to synthesize organic thin films directly on substrates. These thin films are desirable as conformal surface engineering materials and functional layers. The facile tunability of the films and their surface properties allow successful integration of CVD thin films into prototypes for applications in surface modification, device fabrication, and protective films. CVD polymers also bridge microfabrication technology with chemical and biological systems. Robust coatings can be achieved via CVD methods as antifouling, anti-icing, and antihydrate surfaces, as well as stimuli-responsive or biocompatible polymers and novel nanostructures. Use of low-energy input, modest vacuum, and room-temperature substrates renders CVD polymerization compatible with thermally sensitive substrates and devices. Compared with solution-based methods, CVD is particularly useful for insoluble materials, such as electrically conductive polymers and controllably crosslinked networks, and has the potential to reduce environmental, health, and safety impacts associated with solvents. This review discusses the relevant background and selected applications of recent advances by two methods that display and use the high retention of the organic functional groups from their respective monomers, initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization.

Polymer Thin Films and Surface Modification by Chemical Vapor Deposition: Recent Progress.

3-Aminopropyltriethoxysilane (APTES) and perfluorooctyltriethoxysilane (PFES) were used to modify the interface between transferred CVD graphene films and its supporting dielectric to create n-type and p-type graphene, respectively. A graphene p–n junction was obtained by patterning both modifiers on the same dielectric and verified through the creation of a field effect transistor (FET). Characteristic I–V curves indicate the presence of two separate Dirac points which confirms an energy separation of neutrality points within the complementary regions. This method minimizes doping-induced defects and results in thermally stable graphene p–n junctions for temperatures up to 200 °C.

Creating graphene p-n junctions using self-assembled monolayers.

The effect of vacuum annealing followed by exposure to oxygen and water vapor on the unintentional doping of CVD-grown graphene was investigated. CVD graphene samples were cycled between room temperature and 500 °C in vacuum while in situ Raman measurements were recorded. During the heating and cooling cycle, a hysteresis in the Raman response due to the desorption of p-dopants was observed. Upon exposure to O2 gas or air, a blue shift in the Raman response with respect to the as grown film was observed which was due to increased adsorption of p-dopants on the sample. Experiments showed that a combination of water vapor and oxygen is more effective in p-doping the samples than just oxygen and that the doping effects are reversible in both cases. Electrical measurements performed on back-gated field effect graphene devices indicate that shifts in the Dirac point correlate well to the shifts in the Raman peak positions as well as changes found in XPS and Kelvin Probe measurements, verifying the changes in d...

Hossein Sojoudi

Papers

Linker-free grafting of fluorinated polymeric cross-linked network bilayers for durable reduction of ice adhesion

Production of heavily n- and p-doped CVD graphene with solution-processed redox-active metal–organic species

Polymer Thin Films and Surface Modification by Chemical Vapor Deposition: Recent Progress.

Creating graphene p-n junctions using self-assembled monolayers.

Impact of post-growth thermal annealing and environmental exposure on the unintentional doping of CVD graphene films