Ao Liu
Pohang University of Science and Technology · Engineering
About the Lab
Professor Ao Liu's research lab specializes in the development of solution-processed oxide semiconductors and perovskite materials for next-generation optoelectronic devices. The lab focuses on low-temperature fabrication techniques, defect passivation strategies, and dielectric engineering to enhance the performance and stability of thin-film transistors and perovskite solar cells. Key research directions include p-type and n-type oxide semiconductors, high-κ dielectrics, and interface engineering for efficient charge transport and reduced recombination losses. The lab emphasizes scalable, low-cost, and environmentally friendly processing methods for large-area, flexible, and transparent electronics.
Research Overview
Research Output Trend
Figures are computed from collected data and may differ slightly.
Selected Papers
15Compared with the n-i-p structure, inverted (p-i-n) perovskite solar cells (PSCs) promise increased operating stability, but these photovoltaic cells often exhibit lower power conversion efficiencies (PCEs) because of nonradiative recombination losses, particularly at the perovskite/C 60 interface. We passivated surface defects and enabled reflection of minority carriers from the interface into the bulk using two types of functional molecules. We used sulfur-modified methylthio molecules to pass
Abstract The p-type characteristic of solution-processed metal halide perovskite transistors means that they could be used in combination with their n-type counterparts, such as indium–gallium–zinc-oxide transistors, to create complementary metal–oxide–semiconductor-like circuits. However, the performance and stability of perovskite-based transistors do not yet match their n-type counterparts, which limit their broader application. Here we report high-performance p-channel perovskite thin-film t
Abstract The electronic functionalities of metal oxides comprise conductors, semiconductors, and insulators. Metal oxides have attracted great interest for construction of large‐area electronics, particularly thin‐film transistors (TFTs), for their high optical transparency, excellent chemical and thermal stability, and mechanical tolerance. High‐permittivity (κ) oxide dielectrics are a key component for achieving low‐voltage and high‐performance TFTs. With the expanding integration of complemen
Low‐temperature solution processing opens a new window for the fabrication of oxide semiconductors due to its simple, low cost, and large‐area uniformity. Herein, by using solution combustion synthesis (SCS), p‐type Cu‐doped NiO (Cu:NiO) thin films are fabricated at a temperature lower than 150 °C. The light doping of Cu substitutes the Ni site and disperses the valence band of the NiO matrix, leading to an enhanced p‐type conductivity. Their integration into thin‐film transistors (TFTs) demonst
We reported here "aqueous-route" fabrication of In2O3 thin-film transistors (TFTs) using an ultrathin solution-processed ZrOx dielectric thin film. The formation and properties of In2O3 thin films under various annealing temperatures were intensively examined by thermogravimetric analysis, Fourier transform infrared spectroscopy, and atomic force microscopy. The solution-processed ZrOx thin film followed by sequential UV/ozone treatment and low-temperature thermal-annealing processes showed an a
Here, a simple, nontoxic, and inexpensive “water‐inducement” technique for the fabrication of oxide thin films at low annealing temperatures is reported. For water‐induced (WI) precursor solution, the solvent is composed of water without additional organic additives and catalysts. The thermogravimetric analysis indicates that the annealing temperature can be lowered by prolonging the annealing time. A systematic study is carried out to reveal the annealing condition dependence on the performance
Abstract Here, room‐temperature solution‐processed inorganic p‐type copper iodide (CuI) thin‐film transistors (TFTs) are reported for the first time. The spin‐coated 5 nm thick CuI film has average hole mobility ( µ FE ) of 0.44 cm 2 V −1 s −1 and on/off current ratio of 5 × 10 2 . Furthermore, µ FE increases to 1.93 cm 2 V −1 s −1 and operating voltage significantly reduces from 60 to 5 V by using a high permittivity ZrO 2 dielectric layer replacing traditional SiO 2 . Transparent complementary
Solution‐processed metal‐oxide thin films based on high dielectric constant ( k ) materials have been extensively studied for use in low‐cost and high‐performance thin‐film transistors (TFTs). Here, scandium oxide (ScO x ) is fabricated as a TFT dielectric with excellent electrical properties using a novel water‐inducement method. The thin films are annealed at various temperatures and characterized by using X‐ray diffraction, atomic‐force microscopy, X‐ray photoelectron spectroscopy, optical sp
Developing transparent p-type semiconductors and conductors has attracted significant interest in both academia and industry because metal oxides only show efficient n-type characteristics at room temperature. Among the different candidates, copper iodide (CuI) is one of the most promising p-type materials because of its widely adjustable conductivity from transparent electrodes to semiconducting layers in transistors. CuI can form thin films with high transparency in the visible light region us
Abstract ‘Ideal’ transparent p -type semiconductors are required for the integration of high-performance thin-film transistors (TFTs) and circuits. Although CuI has recently attracted attention owing to its excellent opto-electrical properties, solution processability, and low-temperature synthesis, the uncontrolled copper vacancy generation and subsequent excessive hole doping hinder its use as a semiconductor material in TFT devices. In this study, we propose a doping approach through soft che
Solution-processed p-type oxide semiconductors have recently attracted increasing interests for the applications in low-cost optoelectronic devices and low-power consumption complementary metal-oxide-semiconductor circuits. In this work, p-type nickel oxide (NiOx) thin films were prepared using low-temperature solution process and integrated as the channel layer in thin-film transistors (TFTs). The electrical properties of NiOx TFTs, together with the characteristics of NiOx thin films, were sys
Abstract Compared to polycrystalline semiconductors, amorphous semiconductors offer inherent cost-effective, simple and uniform manufacturing. Traditional amorphous hydrogenated Si falls short in electrical properties, necessitating the exploration of new materials. The creation of high-mobility amorphous n-type metal oxides, such as a-InGaZnO (ref. 1 ), and their integration into thin-film transistors (TFTs) have propelled advancements in modern large-area electronics and new-generation display
High-performance p-type NiO<sub>x</sub> thin-film transistors are fabricated <italic>via</italic> a low-cost solution process and exhibit a high mobility of around 15 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup>.
Research Areas
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