Hyeong Pil Kim

A high efficiency solution processed polymer inverted triple-junction solar cell exhibiting a power conversion efficiency of 11.83%

High efficiency, solution-deposited polymer inverted double- and triple-junction solar cells are demonstrated. The devices are composed of three distinctive photosensitive materials in three distinct subcells, with minimal absorption spectral overlap, and with a bandgap ranging from 1.3 eV to 1.82 eV. A transparent hybrid inorganic organic mixture was introduced as an interconnecting layer to optically and physically connect the subcells. Accordingly, a power conversion efficiency of 10.39% was attained for the double-junction cell and a record high of 11.83% was obtained for the triple-junction cell.

Ambipolar Triple Cation Perovskite Field Effect Transistors and Inverters

Ambipolar perovskite field-effect transistors and inverters with balanced mobilities are demonstrated. Thin-film field-effect-transistor-like inverters are developed, and a maximum gain of 23 in the first quadrant for VDD = 80 V is obtained.

Improving the lifetime of a polymer light-emitting diode by introducing solution processed tungsten-oxide

We report a polymer light-emitting diode (PLED) using solution processed tungsten-oxides (WOx). Coating of a thin WOx layer on PEDOT:PSS increases the current efficiency of PLED from 9.11 to 9.90 cd A−1 because of the improved conductivity of the PEDOT:PSS due to the incorporation of WOx. Improvement of the conductivity of PEDOT:PSS promotes hole injection into the emission layer. The lifetime of a PLED with WOx layers on both sides of PEDOT:PSS is 1.8 × 106 h which is around 20 times longer than that of the control device at 1000 cd m−2. The enhanced lifetime is due to the suppression of the indium diffusion from ITO to PEDOT:PSS by WOx and also due to the prevention of acidic damage that can occur to ITO and the organic emission layer by sulfate ions in PEDOT:PSS.

Semi-transparent quantum-dot light emitting diodes with an inverted structure

Semi-transparent quantum-dot light-emitting diodes (QLEDs) can open display applications in many areas, such as energy-saving, aircraft lighting, wallpaper technologies and medical devices. In this paper, the first semi-transparent inverted QLED was demonstrated by using red quantum-dot emissive layer (QD EML). Semi-transparent silver was used as a top electrode deposited by thermal evaporation. The maximum luminance of 10540 cd m−2 was achieved for the semi-transparent inverted QLEDs. The optimized QLED has a maximum transparency of ∼45% in the red-emission region.

Improvement of Conversion Efficiency of Inverted Organic Photovoltaic With PEDOT: PSS:WO x by Thermal Annealing

We report the effects of postannealing on the photovoltaic performance of ITO/LZO/P3HT:ICBA/PEDOT:PSS: WOx/Al. The electrical characteristics of the PEDOT:PSS:WOx film can be controlled through an annealing treatment, which exhibits a short-circuit current density of 9.37 mA/cm2, an open-circuit voltage of 0.86V, and a power conversion efficiency of 5.54% under AM1.5 illumination (100 mW/cm2). By annealing the device at 150°C, a favorable phase separation in the PEDOT:PSS:WOx is obtained, and the PCE increases by 23.27% compared with that of the nonannealed device. The Voc increases with the annealing temperature, and it is worth noting that the PEDOT:PSS device only experienced a 2.40% decrease in PCE after 150°C annealing treatment.

A high performance organic photovoltaic utilizing PEDOT:PSS and graphene oxide

Interface engineering may lead to a high performance organic photovoltaic as well as long lifetime. Incorporating the commonly used conducting polymer PEDOT:PSS with GO as an the anode interfacial layer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7):fullerene derivative (PC71BM) bulk heterojunction (BHJ) organic photovoltaics (OPVs) were fabricated. This conventional OPV demonstrated a power conversion efficiency (PCE) of 7.53%, which has outperformed the highest reported PEDOT:PSS combined metal oxide, the highest reported efficiency with a solution processed PEDOT:PSS:GO interfacial layer as well as a PEDOT:PSS-based OPV (reference device). Moreover, the versatility of PEDOT:PSS:GO has also been demonstrated in the medium bandgap BHJ system employing poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] paired with PC71BM yielding an astonishing high PCE of 9.12%. We believe proper interface engineering could lead to high performance devices.

Integrated optoelectronic model for organic solar cells based on the finite element method including the effect of oblique sunlight incidence and a non-ohmic electrode contact

We present an integrated optoelectronic model for organic solar cells (OSCs) based on the finite element method, which can numerically simulate the optical and electrical properties in the same calculation domain. In the optical model, the spatial distribution of optical absorption is calculated with respect to the incidence angle and light polarization. A glass factor is introduced to include the incoherent light interaction inside the thick glass substrate. In the electrical model, the current density–voltage (J–V) characteristics can be calculated by self-consistently solving the combined equations based on the Onsager–Braun charge-transfer exciton dissociation, drift-diffusion carrier transport, and non-ohmic contact models. The calculation results of the carrier density, the electric potential, and the electric field in the active layer are compared between the ohmic and non-ohmic contact models at the electrode–organic interface. We numerically calculate the angular and polarization dependences of the short-circuit current density, the open-circuit voltage, and the output electric power density at the spectral irradiance of the AM 1.5 spectrum. The calculation results are well matched with the experimental results at various incidence angles and light polarizations. The application of the proposed integrated optoelectronic model to OSCs will not be restricted to one-dimensional planar structures and can be extended to nonplanar or surface-textured structures.