이윤석 교수

11.6%-efficiency Cu2ZnSnSe4 (CZTSe) thin-film solar cells are fabricated via a thermal co-evaporation method. The CZTSe thin film with improved microstructure exhibits a minority carrier diffusion length over 2 μm, resulting in efficient photogenerated carrier collection in the device. A comparative study of photoluminescence in pure selenide and pure sulfide devices shows reduced band-tailing for the pure selenide phase.

The power conversion efficiency of solar cells based on copper (I) oxide (Cu2 O) is enhanced by atomic layer deposition of a thin gallium oxide (Ga2 O3 ) layer. By improving band-alignment and passivating interface defects, the device exhibits an open-circuit voltage of 1.20 V and an efficiency of 3.97%, showing potential of over 7% efficiency.

We demonstrate a tunable electron-blocking layer to enhance the performance of an Earth-abundant metal-oxide solar-cell material. A 5 nm thick amorphous ternary metal-oxide buffer layer reduces interface recombination, resulting in sizable open-circuit voltage and efficiency enhancements. This work emphasizes the importance of interface engineering in improving the performance of Earth-abundant solar cells.

Cuprous oxide (Cu2O) is a promising earth-abundant semiconductor for photovoltaic applications. We report Hall mobilities of polycrystalline Cu2O thin films deposited by reactive dc magnetron sputtering. High substrate growth temperature enhances film grain structure and Hall mobility. Temperature-dependent Hall mobilities measured on these films are comparable to monocrystalline Cu2O at temperatures above 250 K, reaching 62 cm2/V s at room temperature. At lower temperatures, the Hall mobility a

We demonstrate the potential of a nitrogen-doped cuprous oxide (Cu2O:N) film as a p-type hole-transporting layer for photovoltaic devices. To reduce back-contact resistance and create an electron-reflecting back surface field, high carrier density and appropriate work function are desired for the layer. Its electrical and optical properties can be appropriately tuned via nitrogen-doping to create a semi-transparent tunnel junction to a back-contact. We fabricate Cu2O-based heterojunction thin-fi

Nanometer-scale-thick Al2O3 thin films grown by atomic layer deposition are implemented as an effective interface-passivation strategy for improving Cu2ZnSn(S,Se)4-based thin-film solar cell device performance. Photoluminescence characterization indicates that the enhancement originates from improved interface quality of the solar cell devices.

Abstract Although there have been significant advances in the stability of perovskite solar cells through encapsulation techniques to remove extrinsic degradation factors, such as moisture and oxygen, irreversible photo‐degradation originating from intrinsic defects is still challenging and remains elusive. Herein, the photo‐aging mechanism due to intrinsic defects is investigated in nitrogen‐filled conditions, excluding extrinsic degradation factors. Devices with similar power conversion effici

Abstract Cross‐point arrays of synaptic devices have been investigated as a core platform for neuromorphic computing architectures. To achieve a significant speed boost in deep neural network computations compared to the von Neumann architecture, it is essential to develop synaptic devices with optimal performance for fully parallel vector‐matrix‐multiplication. Among various non‐volatile memory candidates, metal‐oxide based electrochemical random‐access memory (ECRAM) is considered as a promisi

Abstract Cross‐point arrays of analog synaptic devices are expected to realize neuromorphic computing hardware for neural network computations with compelling speed boost and superior energy efficiency, as opposed to the conventional hardware based on the von Neumann architecture. To achieve desired characteristics of analog synaptic devices for fully parallel vector–matrix multiplication and vector–vector outer‐product updates, metal‐oxide based electrochemical random‐access memory (ECRAM) is p

Solar thermal distillation is a promising way to harvest clean water due to its sustainability. However, the energy density of solar irradiation inevitably demands scalability of the systems. To realize practical applications, it is highly desirable to fabricate meter-scale solar evaporator panels with high capillary performance as well as optical absorptance using scalable and high-throughput fabrication methods. Here, we demonstrate a truly scalable fabrication process for a bi-facial solar ev

We investigate earth abundant materials for thin-film solar cells that can meet tens of terawatts level deployment potential. Candidate materials are identified by combinatorial search, large-scale electronic structure calculations, and literature reviews. We identified cuprous oxide (Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) as a prototype candidate for investigation as an absorber layer in thin film solar cells. Cu <sub xmlns:m

Defect passivation using two-dimensional (2D)-layered perovskites with organic spacers on 3D bulk perovskites has been proposed as an effective strategy to improve perovskite solar cell stability and efficiency. Specifically, fluorination of the organic spacers has been employed due to the resulting hydrophobic nature and the defect passivation characteristics. In addition to the type of functional groups attached to the spacer molecules, conformational changes of fluorine isomers on layered per

Solar cells that are semitransparent and highly efficient can find diverse applications in automobile windows, building walls, and wearable devices. Here, we present a semitransparent perovskite thin-film solar cell with an Ag nanogrid transparent electrode, where electrospun poly(ethylene oxide) (PEO) nanofibers are used as an etching mask. Directional electrospinning has allowed us to obtain a grid-shaped electrode of well-aligned Ag nanogrids. The performance of transparent electrodes can be

Abstract In 2004, K. S. Novoselov and A. K. Geim et al. have used sellotape to peel off the layered 2D graphite, and successfully obtained few‐layer thin graphene. Inspired by this, herein, the sellotape is initially used to exfoliate the layered Ruddlesden–Popper (RP) quasi‐2D perovskite film for efficient light‐emitting diodes application. The top surface layer of quasi‐2D perovskite film is mechanically peeled off by the sellotape without damaging the crystalline region below, which minimizes