Kyungkon Kim

The authors have fabricated thin film polymer photovoltaics using 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61 within regioregular poly(3-hexylthiophene) bulk heterojunction absorbing layers. Using thermal annealing at temperatures approaching the glass transition temperature, they have examined the formation of nanodomains within the matrix. These domains modify charge transport pathways in such a way as to allow for the efficient use of thicker absorbing layers. This results in a nearly 20% g

We obtained improved poly(3-octylthiophene) (P3OT)/C60 bulk heterojunction photovoltaic devices by doping with stable and highly electrically conductive Au and Ag nanoparticles. Doped devices showed 50–70% improved efficiency, with the Ag nanoparticles exhibiting the greatest increase in efficiency. We suggest that a dominate mechanism for the efficiency enhancement of doped photovoltaic device is the improved electrical conductivity through the introduction of “dopant” levels within the band ga

A series of thienyl-substituted methanofullerenes as electron acceptors for bulk-heterojuction solar cells with poly(3-hexylthiophene) (P3HT) were synthesized and characterized with respect to electrochemical and photophysical properties. The first one-electron reduction potentials of the higher adducts are shifted toward more negative values by ∼100 mV as compared to the monoadduct. As a result, the solar cells composed of the bisadduct (2) and trisadduct exhibit a larger open-circuit voltage (

We report the synthesis of poly(p-phenylene vinylene) (PPV), a polyconjugated polymer, in nanotube and nanorod shapes, and carbonized products derived therefrom. PPV tubes and rods could be prepared on the inner surface of or inside the nanopores (10−200 nm diameter) in alumina or polycarbonate membrane filters by the chemical vapor deposition (CVD) polymerization method of α,α‘-dichloro-p-xylene followed by thermal dehydrochlorination. The PPV nanotubes and nanorods thus obtained could be conve

Abstract Colorful, semitransparent organic photovoltaic cells (OPVs) are increasing in demand due to their applicability in aesthetically fashioned power‐generating windows. The traditional method of generating different colors in OPVs has been through employing different active materials exhibiting distinct absorption spectra. This can complicate fabrication processes for production and cause deviations in device performance among differently colored OPVs. Herein, semitransparent and colorful O

New organic soluble poly(p-phenylenevinylene) (PPV) derivatives (polymers 1 and 2) that carry hole-transporting carbazole pendants were synthesized and their photo- and electro-luminescence properties were studied. The first one is poly[2-(carbazol-9-yl)-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (polymer 1) which has both carbazole and 2-ethylhexyloxy pendant groups. The other one is poly[2-(carbazol-9-yl)-1,4-phenylenevinylene] (polymer 2) which has only the carbazole pendant group attached to

Abstract Developing an effective scalable fabrication process for perovskite solar cells is urgent to getting perovskite photovoltaic technology market‐ready. Perhaps due to the relatively cost‐effective setup and tunable fabrication processes, the vast majority of research efforts have been dedicated to the development of solution‐based scalable processes. Comparatively, the vacuum thermal evaporation processes have not been studied in‐depth, regardless of their advantages in reproducibility, s

An efficient CH₃NH₃PbI₃ perovskite solar cell whose performance is reproducible and shows reduced dependence on the processing conditions is fabricated using the cyclic urea compound 1,3-dimethyl-2-imidazolidinone (DMI) as an additive to the precursor solution of CH₃NH₃PbI₃. X-ray diffraction analysis reveals that DMI weakly coordinates with PbI₂ and forms a CH₃NH₃PbI₃ film (film-DMI) wi

We have fabricated bulk heterojunction (BHJ) photovoltaic (PV) devices by thermal annealing of poly-3-hexylthiophene (P3HT)/C60 single heterojunction (HJ) PV devices at near the melting point of P3HT. The BHJ PV devices exhibited an increased efficiency of 12 times compared with single HJs. We found that the annealing of HJ devices produces an interpenetrated network of interfaces between the P3HT and C60 layers. This plays a major role in carrier separation and mobility enhancement. Also the fo

An efficient hole-transporting layer (HTL) based on functionalized two-dimensional (2D) MoS₂-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composites has been developed for use in organic solar cells (OSCs). Few-layer, oleylamine-functionalized MoS₂ (FMoS₂) nanosheets were prepared via a simple and cost-effective solution-phase exfoliation method; then, they were blended into PEDOT:PSS, a conducting conjugated polymer, and the resulting hybr

A ternary solvent system consisting of dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL) and N-methyl-2-pyrrolidone (NMP) has been developed to improve the uniformity of CH₃NH₃PbI₃ (MAPbI₃) perovskite domains. Compared to MAPbI₃ perovskite films prepared using a binary solvent consisting of DMSO and GBL, the surface roughness and uniformity of MAPbI₃ films fabricated by using the ternary solvent system are greatly improved. The the

We describe the preparation and characterization of a photonic crystal filled with a luminescent conjugated polyelectrolyte, sulfonated poly(phenylene ethynylene). The conjugated polymer was coated onto the nanospheres by the layer-by-layer method and assembled directly into a fluorescent opal structure avoiding the defects associated with post-filling schemes. These structures exhibit strong angle-dependent luminescent properties. By using multiple layers, we further demonstrate control over th