Jaemin Kong

Gyeongsang National University | GNU

Solution‐processed transition metal oxides (TMOs) prepared from complex ion precursors are developed as promising scalable interfacial layers for non‐fullerene organic photovoltaics (OPVs); however, challenges remain in achieving defect‐free and highly oriented metal‐oxygen networks without post‐deposition treatments due to the presence of residual...

Improving solar energy collection in aquatic environments would allow for superior environmental monitoring and remote sensing, but the identification of optimal photovoltaic technologies for such applications is challenging as evaluation requires either field deployment or access to large water tanks. Here, we present a simple bench-top characteri...

Tin dioxide (SnO2) is a frequently reported electron transporting material for perovskite solar cells that yields high performance devices and can be solution processed from aqueous colloidal solutions. While being very simple to process, electron transport layers deposited in this manner often lead to non-uniform film morphology, significantly aff...

s Polymer composites are recently being deployed to buildings and vehicles that are required to meet both load-bearing properties and aesthetic needs. Since color is one of the most essential elements of a design, coloring of structural composites is drawing great attention. Despite various attempts of coloration of polymer composites, there is a l...

Improving solar energy collection in aquatic environments would allow for superior environmental monitoring and remote sensing, but the identification of optimal photovoltaic technologies for such applications is challenging as evaluation requires either field deployment or access to large water tanks. Here, we present a simple bench-top characteri...

Chemical and electronic sensitization in metal oxide gas sensors are severely limited by poor dimension controls of metal oxide nanostructure and their electric/electronic properties. These limitations are overcome using hydrothermal-induced heterointerface engineering approaches. This work demonstrates that forming spherical titanium dioxide nanop...

In perovskite solar cells, doped organic semiconductors are often used as charge-extraction interlayers situated between the photoactive layer and the electrodes. The π-conjugated small molecule 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9-spirobifluorene (spiro-OMeTAD) is the most frequently used semiconductor in the hole-conducting layer1...

Continuous fiber reinforcements are widely used to enhance mechanical properties of composite materials, but the impregnation of continuous fiber reinforcements with thermoplastics is a challenge due to high melt viscosity of the thermoplastic matrix. One of promising routes to improve the impregnation is to prepare commingled yarns with continuous...

Despite significant advancements in reinforcing material-embedded structural adhesives, the industry still hesitates to employ the new technologies in their production line. In this communication, we investigate what critically hampers the practical application of newly developed reinforcing material-embedded structural adhesives to the industry, a...

Despite huge improvements in power conversion efficiencies of perovskite solar cells, the technology is still limited by fill factors at around 80%. Here, we report perovskite solar cells having exceptionally high fill factors of 85% and enhanced open-circuit voltage without sacrificing short-circuit current through a polymer-capped solvent anneali...

Two-dimensional transition metal carbides and nitrides (MXenes) have accumulated tremendous interest recently due to their high conductivity and excellent figures of merit in electromagnetic interference shielding and other applications. Large-area freestanding films of MXenes are important for versatility in application; however, alternative proce...

Operation of underwater vehicles and autonomous systems is currently limited by the lack of long-lasting power sources. These systems could potentially be powered using underwater solar cells, but the material requirements to achieve their full potential are not well-understood. Using detailed-balance calculations, we show that underwater solar cel...

Operation of underwater vehicles and autonomous systems is currently limited by the lack of long-lasting power sources. These systems could potentially be powered using underwater solar cells, but the material requirements to achieve their full potential are not well-understood. Using detailed-balance calculations, we show that underwater solar cel...

Polymer nanocomposites offer the opportunity to bridge properties of nanomaterials to the macroscale. In this work, layer-by-layer (LbL) assembly is used to demonstrate nanocomposites of 2D titanium carbide nanosheets (MXene) and clay nanoplatelets (montmorillonite) to fabricate freestanding thin films with unique multifunctional properties. These...

Two‐dimensional graphitic carbon nitride (g‐C3N4) nanosheet is a promising negative electrode candidate for sodium‐ion batteries (NIBs) owing to its easy scalability, low cost, chemical stability and potentially high rate capability. However, intrinsic g‐C3N4 exhibits poor electronic conductivity, low reversible Na‐storage capacity and insufficient...

Two‐dimensional graphitic carbon nitride (g‐C3N4) nanosheet is a promising negative electrode candidate for sodium‐ion batteries (NIBs) owing to its easy scalability, low cost, chemical stability and potentially high rate capability. However, intrinsic g‐C3N4 exhibits poor electronic conductivity, low reversible Na‐storage capacity and insufficient...

Batteries coupled to photovoltaic (PV) modules have been identified as a viable power source for independent “internet of things” portable electronic devices and to reduce the grid load during peak times. However, the poor matching of these systems can adversely affect the power conversion efficiency, safety, and cost due to increased charge contro...

Electron acceptor degradation of organic solar cells is considered a main contributor to performance instability and a barrier for the commercialization of organic solar cells. Here, we selectively remove the electron acceptors on the surface of donor:acceptor blend films using a tape stripping technique. The near edge X-ray absorption fine structu...

Cross-sectional potential distribution of high open-circuit voltage bulk heterojunction photovoltaic device was measured using Kelvin probe force microscopy. Potential drop confined at cathode interface implies that photo-active layer is an effective p-type semiconductor. Potential values in field-free region show wide variation according to log-no...

Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness are highly desirable for next‐generation portable and wearable electronic devices. Here, spin spray layer‐by‐layer (SSLbL) to rapidly assemble Ti3C2Tx MXene‐carbon nanotube (CNT) composite films is shown and their poten...

The successful commercialization of perovskite solar cells (Pvs-SCs) calls for the need to find low-temperature processable interlayers with outstanding charge-transport features. In this work, we strategically blend poly(2-ethyl-2-oxazoline) (PEOz) with PEDOT:PSS as the modified hole transport layer (HTL) to achieve high efficiency P-I-N CH3NH3PbI...

The P-I-N structure for perovskite solar cells has recently shown significant advantages in minimal hysteresis effects, and scalable manufacturing potential using low-temperature solution processing. However, the power conversion efficiency (PCE) of the perovskite p-i-n structure remains low mainly due to limitations using a flat electron transport...

In article number 1700144, Yifan Zheng, Junsheng Yu and co‐workers demonstrate a high efficiency polymer solar cell (PSC) through introducing a novel binary solvent additive combination of DPE:DIO (diphenyl ether und 1,8‐diiodoctane). This binary solvent additive system of DPE:DIO combines the influence of DIO on the PC70BM dispersion together with...

In this work, a 9.5% of power conversion efficiency (PCE) is obtained in the thieno [3,4-b] thiophene/benzodithiophene (PTB7): (6,6)-phenyl-C70-butyric acid methyl ester (PC70BM) based polymer solar cell (PSC) by using a novel binary solvent additive of diphenyl ether (DPE): 1,8-diiodoctane (DIO). We find that this binary solvent additive approach...

Sequentially solution-processed polymer photodetectors (SSP PPDs) based on poly(3-hexylthiophene-2,5-diyl) (P3HT)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) are fabricated by depositing the top layers of PC71BM from an appropriate cosolvent of 2-chlorophenol (2-CP)/o-dichlorobenzene (ODCB) onto the predeposited bottom layers of P3HT. By ad...

Recently two dimensional (2D) organic-inorganic perovskites emerge as an alternative material for their 3D counterparts in photovoltaic applications with improved moisture resistance. Here, we report a stable, high-gain phototransistor consisting of a monolayer graphene on hexagonal boron nitride (hBN) covered by a 2D multiphase perovskite heterost...

Herein, we demonstrate that the lifetimes of polymer-based solar cells comprising PTB7-F20:PC71BM composites can be significantly increased by using post-additive-soaked bulk heterojunction (BHJ) films. Analyses of solar cell performance, film morphology, time-resolved photoluminescence, and photoconductivity revealed that the above increase result...

Improvement of the interface between the perovskite layer and the electron-transport layer (ETL) is critical toward the advancement of planar perovskite solar cells (PSCs). It is important to obtain a uniform and pinhole-free ETL that can minimize film defects and thus undesirable electron–hole recombination between the perovskite layer and cathode...

Over the past decade, there has been significant improvement in the performance of polymer solar cells (PSCs). Devices with power conversion efficiency (PCE) well over 10% have been developed and in some cases the estimated device lifetime is approaching 10 years. In contrast, there has been limited research into the aesthetics of PSCs, which may b...

Despite being the most commonly used hole transport layer for p-i-n perovskite solar cells, the conventional PEDOT:PSS layer is far from being optimal for the best photovoltaic performance. Herein, we demonstrate highly conductive thin DMSO-doped PEDOT:PSS layers which significantly enhance the light harvesting, charge extraction, and photocurrent...

It is observed that degradation of organic bulk heterojunction is directly associated with degradation of solvent additive, 1,8-diiodooctane. The iodide impurities released from 1,8-diiodooctane react with fullerenes, making fullerene-iodide intermediate compounds which lead to fullerene oxidation and efficiency drop, irrespective of photooxidation...

Despite recent reports of high power conversion efficiency (PCE) values of over 20%, the instability of perovskite solar cells (PSCs) has been considered the most serious obstacle toward their commercialization. By rigorously exploring the self-degradation process of planar-type PSCs using typical metal electrodes (Ag or Al), we found that the corr...

Highly efficient P-I-N type perovskite/bulk-heterojunction (BHJ) integrated solar cells (ISCs) with enhanced fill factor (FF) (≈80%) and high near-infrared harvesting (>30%) are demonstrated by optimizing the BHJ morphology with a novel n-type polymer, N2200, and a new solvent processing additive. This work proves the feasibility of highly efficien...

Efficient large-area planar heterojunction (PHJ) perovskite solar cells (PSCs) were successfully developed by adapting a scalable doctor blade printing method under ambient condition. To achieve high-quality perovskite films onto poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer, the PEDOT:PSS was modified by adding poly(4-s...

Improved performance of polymer-based solar cells based on PTB7:PC71BM composites has been obtained by using additive-soaking treatments on pristine bulk-heterojunction (BHJ) films. From analyses of the nanoscale morphologies, solar-cell-device performance, and photoluminescence (PL) characteristics, we found that the best performance predominantly...

Because the fabrication process of organic tandem solar cells described by K. Lee and co-workers on page 1408 is similar to the process for the cooking of cakes, the manufacturing process of cakes (i.e., tandem polymer solar cells) fabricated from various color doughs (i.e., organic electronic inks) is illustrated in the back-cover design so that t...

The inferior long-term stability of polymer-based solar cells needs to be overcome for their commercialization to be viable. In particular, an abrupt decrease in performance during initial device operation, the so-called 'burn-in' loss, has been a major contributor to the short lifetime of polymer solar cells, fundamentally impeding polymer-based p...

A new tandem architecture for printable photovoltaics using a versatile organic nanocomposite containing photoactive and interfacial materials is demonstrated. The nanocomposite forms an ideal self-organized recombination layer via a spontaneous vertical phase separation, which yields a simplified tandem structure fabricated with only four componen...

Vanadium suboxide (VOx) layers deposited by an electro-spray (e-spray) printing method were applied to the fabrication of high efficiency patterned polymer solar cell (PSC) modules. By tailoring surface tension and the atomization condition of the e-sprayed sol precursor, e-sprayed VOx layers on top of both hydrophilic and hydrophobic surfaces were...

'Top-Down' nanophase reconstruction via post-additive soaking process is first presented with various BHJ binary composites. By simply rinsing as-cast BHJ films with a solvent mixture containing a few traces of a nanophase-control reagent such as 1,8-diiodooctane, oversized fullerene-rich clusters (>100 nm in dia-meter) in the BHJ film are instatan...

“Top-Down” nanophase reconstruction via a post-additive soaking process is first presented with various BHJ binary composites. By simply rinsing as-cast BHJ films with a solvent mixture containing a few traces of a nanophase-control reagent such as 1,8-diiodooctane, oversized fullerene-rich clusters (>100 nm in dia­meter) in the BHJ film are instat...

ght-soaking-free inverted polymer solar cell (i-PSC) devices are demonstrated by incorporating nitrogen doped sol–gel titanium sub-oxide (N-TiOx). A heavily doped electron transport layer in i-PSCs, N-TiOx on indium tin oxide yields an Ohmic contact with the bulk heterojunction layer that does not exhibit light-soaking processes. This results in hi...

We developed bulk-heterojunction (BHJ) polymer solar cells (PSCs) by slot-die coating a poly(3-hexylthiophene):fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) composites with various solvents, such as chlorobenzene (CB), dichlorobenzene (DCB), or a CB/DCB co-solvent. To understand the effect of solvent on the uniform act...

While sol–gel-processed metal oxides are widely used as an electron transport layer to enhance photovoltaic performances, their effect on photodetector application was not studied. We found sol–gel-processed titanium oxide deteriorated dark current characteristics in reverse biases by almost two orders of magnitude, whereas bare Al cathodes exhibit...

An innovative method for achieving depletion-free recombination layers (RLs) in inverted tandem polymer solar cells is demonstrated using ionic self-assembly of a cationic non-conjugated polyelectrolyte and an anionic metallic polymer. These RLs form tunnel junctions with different work functions of 5.1 eV and 3.9 eV on each of their surfaces. The...

An efficient module cell architecture of a polymer solar cell built upon self-aligned alternating interfacial layers is presented. Alternating conventional and inverted subcells are serially connected on a single compound electrode with self-aligned interfacial layers. A high relative power conversion efficiency of 82% of the large-area module cell...

We investigated the effect of active layer thickness on recombination kinetics of poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) based solar cells. Analysis of the fitted Lambert W-function of illuminated current density–voltage (J–V) cha...

Additional post-processing techniques, such as post-thermal annealing and UV illumination, were found to be required to obtain desirable values of the cell parameters in a tandem polymer solar cell incorporated with solution-processed basic n-type titanium sub-oxide (TiO(x))/acidic p-type poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PED...

The effect of active-area scale-down and improved memory performance of solution-processed $\hbox{TiO}_{x}$ were investigated using devices with active areas ranging from $\hbox{50} \times \hbox{50}\ \mu\hbox{m}^{2}$ to $\hbox{200} \times \hbox{200}\ \hbox{nm}^{2}$. As the active area decreases, higher operation voltages were required owing to the...

External-biased potential distributions of a polymer bulk-heterojunction (BHJ) solar cell, incorporated with electron/hole transporting layers, were directly obseved through a cross-sectional Kelvin probe force microscopy. The bulk electric field of BHJ was found to be nearly field-free even under reverse biases, and the field-free region was probe...

a b s t r a c t We propose and demonstrate a new series connection method that employs alternating conventional and inverted bulk-heterojunction (BHJ) solar cells. The two adjacent cells in each submodule are connected through top or bottom 'continuous terminals' made of aluminum or indium tin oxide (ITO), which are shared by cells with different p...

Cross-sectional potential distributions of a polymer bulk heterojunction (BHJ) solar cell, consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester blends, were directly observed by using Kelvin probe force microscopy. It was found that the bulk electric field of BHJ is nearly field-free compared with that of class...

We demonstrated a flexible resistive random access memory (FReRAM) device using a solution-processed TiOx active layer with an Al top electrode on an Ag layer-inserted indium-zinc-tin-oxide (IAI)-coated polyethersulfone substrate (Al/TiOx/IAI). Its feasibility of FReRAM application was evaluated through the comparison of electrical and mechanical c...

Solution-processed TiOx layer was investigated as a candidate for next-generation resistive random access memory (ReRAM) application. TiOx active layer was prepared by simple spin coating process of a titanium(IV) isopropoxide precursor using sol–gel chemistry. Through the introduction of indium-tin-oxide (ITO) coated glass and polyethersulfone (PE...

We demonstrated analog memory, synaptic plasticity, and a spike-timing-dependent plasticity (STDP) function with a nanoscale titanium oxide bilayer resistive switching device with a simple fabrication process and good yield uniformity. We confirmed the multilevel conductance and analog memory characteristics as well as the uniformity and separated...

Resistive switching characteristics of bilayered titanium oxides layer were investigated. To improve the relatively poor electrical characteristics of solution-processed TiOx active layers, we incorporated an additional thin TiO2 (~8 nm) layer by atomic layer deposition. The bilayered titanium oxide active layer showed a significantly improved perf...

Resistive switching characteristics of bilayered titanium oxides layer were investigated. To improve the relatively poor electrical characteristics of solution-processed TiOx active layers, we incorporated an additional thin TiO2 (˜8 nm) layer by atomic layer deposition. The bilayered titanium oxide active layer showed a significantly improved perf...

We propose a solution-processed transparent TiO(x)-based resistive switching random access memory (ReRAM) device. Electronically active TiO(x) was prepared by sol-gel spin coating of a titanium(IV) isopropoxide precursor on an indium tin oxide-coated glass. The prepared TiO(x) film is completely transparent in the visible range and has an amorphous...

In this study, we successfully demonstrated ReRAM device with active area below 1 ¿m2, using solution-processed TiO¿ in via-hole structures.