Perovskite Light-Emitting Diodes via Laser Crystallization: Systematic Investigation on Grain Size Effects for Device Performance.

Owing to unique potential for high color purity luminance based on low-cost solution processes, organic/inorganic hybrid perovskite light-emitting diodes (PeLEDs) are attracting a great deal of research attention. For high performance PeLEDs, optimum control of the perovskite film morphology is a critical parameter. Here, we introduce a reliable and well-controllable PeLED crystallization process based on beam-damage-free near-infrared laser (λ = 808 nm) irradiation. Morphology of the CH3NH3PbBr3 films can be precisely controlled by laser irradiation condition parameters: power density and beam scan rate. We systematically investigate the perovskite film morphology and device performance of the PeLEDs under different processing conditions. In the optimum power density and high beam scan rate (30 W cm-2, 0.1 mm s-1), a dense and smooth perovskite film is attained with a small crystal grain size. The critical relationship between the crystal grain size and LED efficiency is established while attaining the device performance of 0.95 cd A-1 efficiency and 1784 cd m-2.

Laser Crystallization of Organic-Inorganic Hybrid Perovskite Solar Cells.

Organic-inorganic hybrid perovskites attract enormous research interest for next generation solar energy harvest. Synergistic crystalline structures comprising organic and inorganic components enable solution processing of perovskite films. A reliable crystallization method for perovskites, compatible with fast continuous process over large-area flexible substrates, is crucial for high performance solar cell production. Here, we present laser crystallization of hybrid perovskite solar cells using near-infrared (NIR) laser (λ = 1064 nm). Crystalline morphology of CH3NH3PbI3 (MAPbI3) perovskite films are widely controllable with laser irradiation condition while maintaining film uniformity. Photothermal heating effectively assisted by interfacial photoconversion layers is critical for phase transformation without beam damage of multilayered device structures. Notably, laser crystallization attains higher device performances than conventional thermal annealing. Fast laser crystallization with manufacture level scan rate (1 m min(-1)) demonstrates inverted-type perovskite solar cells with 11.3 and 8.0% efficiencies on typical glass and flexible polymer substrates, respectively, without rigorous device optimization.

Synergistic concurrent enhancement of charge generation, dissociation, and transport in organic solar cells with plasmonic metal-carbon nanotube hybrids.

Plasmonic nanostructures are synthesized by decorating B- or N-doped carbon nanotubes (CNTs) with Au nanoparticles. While the plasmonic nanoparticles promote exciton generation and dissociation, the B- and N-doped CNTs enable charge-selective transport enhancement in the organic active layer. Such concurrent enhancements of all the principal energy-harvesting steps improve the device efficiency up to 9.98% for organic single-junction solar cells.

High performance organic photovoltaics with plasmonic-coupled metal nanoparticle clusters.

Performance enhancement of organic photovoltaics using plasmonic nanoparticles has been limited without interparticle plasmon coupling. We demonstrate high performance organic photovoltaics employing gold nanoparticle clusters with controlled morphology as a plasmonic component. Near-field coupling at the interparticle gaps of nanoparticle clusters gives rise to strong enhancement in localized electromagnetic field, which led to the significant improvement of exciton generation and dissociation in the active layer of organic solar cells. A power conversion efficiency of 9.48% is attained by employing gold nanoparticle clusters at the bottom of the organic active layer. This is one of the highest efficiency values reported thus far for the single active layer organic photovoltaics.

Bismuth-catalyzed and doped silicon nanowires for one-pump-down fabrication of radial junction solar cells.

Silicon nanowires (SiNWs) are becoming a popular choice to develop a new generation of radial junction solar cells. We here explore a bismuth- (Bi-) catalyzed growth and doping of SiNWs, via vapor-liquid-solid (VLS) mode, to fabricate amorphous Si radial n-i-p junction solar cells in a one-pump-down and low-temperature process in a single chamber plasma deposition system. We provide the first evidence that catalyst doping in the SiNW cores, caused by incorporating Bi catalyst atoms as n-type dopant, can be utilized to fabricate radial junction solar cells, with a record open circuit voltage of V(oc) = 0.76 V and an enhanced light trapping effect that boosts the short circuit current to J(sc) = 11.23 mA/cm(2). More importantly, this bi-catalyzed SiNW growth and doping strategy exempts the use of extremely toxic phosphine gas, leading to significant procedure simplification and cost reduction for building radial junction thin film solar cells.

Solution, solid state, and film properties of a structurally characterized highly luminescent molecular europium plastic material excitable with visible light.

The synthesis and X-ray crystal structure of the ligand L (4,7-dicarbazol-9-yl-[1,10]-phenanthroline) are reported, as well as those of the molecular complex, [Eu(tta)(3)(L)] (1), (tta = 2-thenoyl trifluoroacetylacetonate). Their photophysical properties have been investigated both in solution and in the solid state. It was shown that the ligands used for designing 1 are well-suited for sensitizing the Eu(III) ion emission, thanks to a favorable position of the triplet state as investigated in the Gd(III) complex [Gd(tta)(3)(L)], (2). The low local symmetry of the Eu(III) ion shown by the X-ray crystal structure of 1 is also revealed by luminescence spectroscopy. Because of interesting volatility and solubility properties, 1 is shown to behave as a real molecular material that can be processed both by thermal evaporation and from solution. When doped in poly(methylmethacrylate) (PMMA), 1 forms air-stable and highly red-emitting plastic materials that can be excited in a wide range of wavelengths from the UV to the visible part of the electromagnetic spectrum (250-560 nm). Absolute quantum yields of 80% have been obtained for films comprising 1-3% of 1. Ellipsometry measurements have been introduced to gain information on physical data of 1. They have been performed on thin films of 1 deposited by thermal evaporation and gave access to the refractive index, n, and the absorption coefficient, k, as a function of the wavelength. A value of 1.70 has been found for n at 633 nm. These thin films also show interesting air-stability.