Hyesung Shin

With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generati

NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm i

A template-directed synthesis strategy is an ideal tool to fabricate oxide nanotubes in that their physical dimensions can be precisely controlled and monodisperse samples can be harvested in large quantity. The wall thickness of the oxide nanotubes is controllable by varying the deposition conditions, and the length and diameter can be tailored in accordance with the templates used. A wealth of functional oxide materials with the controlled polymorphs can be deposited to be nanotubular structur

Despite the high power conversion efficiency (PCE) of perovskite solar cells (PSCs), poor long-term stability is one of the main obstacles preventing their commercialization. Several approaches to enhance the stability of PSCs have been proposed. However, an accelerating stability test of PSCs at high temperature under the operating conditions in ambient air remains still to be demonstrated. Herein, interface-engineered stable PSCs with inorganic charge-transport layers are shown. The highly con

Abstract Insufficient charge extraction at the interfaces between light‐absorbing perovskites and charge transporting layers is one of the drawbacks of state‐of‐the‐art perovskite solar cells. Surface treatments and/or interface engineering are necessary to approach the Shockley–Queisser limit. In this work, novel 2D layered perovskites, such as CHA 2 PbI 4 (CHAI = cyclohexylammonium iodide) and CHMA 2 PbI 4 (CHMAI = cyclohexylmethylammonium iodide), are introduced in between 3D perovskites and

Organic-inorganic hybrid metal halides are now the most attractive photovoltaic absorber materials, typically, methylammonium lead triiodides (MAPbI3). These unique semiconducting materials as absorbers demonstrate a remarkably improved power conversion efficiency of over 20% and now with a certified efficiency of 23.3%. Considering the Shockley-Queisser limit and their bandgaps, there is still much room to increase the efficiency. Stable devices with reproducibility and long-term use are essent

High-efficiency planar type perovskite solar cells were fabricated by atomic layer deposition (ALD) of SnO2 and subsequent annealing at 180 °C. As-dep. SnO2 layers prepared by post-annealing at 180 and 300 °C, respectively, were used as electron transporting layers (ETLs). ALD-TiO2 layers were also prepared by post annealing at 400 °C, and the thicknesses of all ETLs were around 12 nm. PL quenching, optical band gap measurement, UPS, and conductive AFM results show that SnO2 can more appropriate

Both enhancing the excitons' lifetime and ingeniously controlling the spatial charge transfer are the key to the realization of efficiently photocatalytic and artificially photosynthetic devices. Nanostructured metal/metal-oxide interfaces often exhibit improved energy conversion efficiency. Understanding the surface potential changes of nano-objects under light illumination is crucial in photoelectrochemical cells. Under ultraviolet (UV) illumination, here, we directly observed the charge separ

Organic–inorganic hybrid perovskite solar cells are attracting the attention of researchers owing to the high level of performance they exhibit in photovoltaic device applications. However, the attainment of an even higher level of performance is hindered by their anomalous current–voltage ( I – V ) hysteresis behavior. Even though experimental and theoretical studies have suggested that the perovskite materials may have a ferroelectric nature, it is still far from being fully understood. In thi

Abstract A general methodology is reported to create organic–inorganic hybrid metal halide perovskite films with enlarged and preferred‐orientation grains. Simply pressing polyurethane stamps with hexagonal nanodot arrays on partially dried perovskite intermediate films can cause pressure‐induced perovskite crystallization. This pressure‐induced crystallization allows to prepare highly efficient perovskite solar cells (PSCs) because the preferred‐orientation and enlarged grains with low‐angle gr

We describe the direct preparation of crystalline Ni₃S₂ thin films via atomic layer deposition (ALD) techniques at temperatures as low as 250 °C without postthermal treatments. A new ALD chemistry is proposed using bis(1-dimethylamino-2-methyl-2-butoxy) nickel(II) [Ni(dmamb)₂] and H₂S as precursors. Homogeneous and conformal depositions of Ni₃S₂ films were achieved on 4 in. wafers (both metal and oxide substrates, including Au and

The edge sites of molybdenum disulfide (MoS 2 ) have been shown to be efficient electrocatalysts for the hydrogen evolution reaction (HER). To utilize these structures, two main strategies have been proposed. The first strategy is to use amorphous structures, which should be beneficial in maximizing the area of the edge-site moieties of MoS 2 . However, these structures experience structural instability during HER. The other strategy is nanostructuring, in which, to enhance the resulting HER per

Abstract Resistive memory switching devices based on transition metal oxides are now emerging as a candidate for nonvolatile memories. To visualize nano‐sized (10 nm to 30 nm in diameter) conducting filamentary paths in the surface of NiO thin films during repetitive switching, current sensing–atomic force microscopy and ultra‐thin (<5 nm) Pt films as top electrodes were used. Some areas (or spots), which were assumed to be the beginning of the conducting filaments, appeared (formation) and d