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Department of Energy EngineeringOrganic solar cells (OSCs), a kind of promising photovoltaics in next generation due to lots of advantages such as mechanical flexibility, light weight, easy bandgap tuning, easy fabrication and so on, is direct conversion system from sunlight to electricity through the absorption of photons in active materials. Since light consist of radiant particles (photons) and electromagnetic field (waves) is necessary to work solar cells, there is promising route to enhance the performance of OSCs via combination of the inherent potential in organic solar cells and optical engineering. Furthermore, the studies using light manipulation are expected not only to lead to commercialization of OSCs, but also to use in other optoelectronics engineering as strategies. The main research is as follows. Firstly, the localized surface plasmon resonance (LSPR) phenomenon generated by light is used in organic solar cells, which arise from two different electron transport layers (ETLs) incorporated with silver (Ag) nanoparticles. According to Mie theory for spherical particles, the LSPR frequency changes depending on the refractive index of surroundings, which shows the different influence and improvement of performance on organic solar cells. In addition, for this study, we used block copolymer micellar lithography (BCML) for Ag dot arrays, optical calculation considering quantum size effect, nonlocal response and plasmon coupling effects. Secondly, to broaden photon absorption without the light waste, hetero organic tandem solar cells (HOTSCs) were fabricated by accounting into limited factors of tandem structure system as well as requirements of each layers. In this study, two new polymers of wide band gap were used in bottom solar sub-cells, while relatively narrower bandgap polymer was used in top solar sub-cells. Thus, the tandem solar cells in series shows high performance with increased open-circuit voltage (Vocs). Thirdly, semitransparent organic solar cells were studied with transparent electrodes based on multilayers of metal and metal oxide. Since organic photoactive layers are so colorful that OSCs are suitable for building-integrated photovoltaics (BIPV), transparent top electrodes were key for semitransparent device. Using Sb2O3 layers in dielectric-metal-dielectric (DMD) structure, not only colorful semitransparent solar cells with over around 30% of average visible transmittance (AVT: 380 nm ??? 780 nm) were fabricated, but also roles of each layers of DMD electrode were studied. Further, as forth topic, colorant-based electrodes are also interesting approach for colorful semitransparent OSCs. The structure of color filter is reverse to DMD transparent electrode, which has configuration of metal-metal oxide-metal. Incorporating DMD electrode and color filter electrode, high performance and selective clear-colorful semitransparent OSCs were implemented. These optic engineering of metal and metal oxide layers and light manipulation will provide breakthroughs for innovative OSCs. In addition, as sub-research (Chapter 6-10), I also studied controlling morphologies and molecular packing structures of photoactive films with various conjugated donor polymers, which were modified side chains on the backbones, and processing method including thermal-, additives-, solvent treatment and so on. Finally, I suggest the potential of flexible OSCs fabricated by a roll-to-roll (R2R) process without performance loss through dual thermal treatment of slot die coating for optimal film morphology and molecular orientation. These strategic approaches from light manipulation and trying film optimization of various polymers and processing methodology may draw realization of aesthetic OSCs commercial market.clos

Carbon Emission Regulation, Green Boards, and Corporate Environmental Responsibility

In this study, we examine various effects of carbon emission regulation enacted in South Korea. We provide empirical evidence of regulated firms strategically hedging against potential risks by increasing the number of directors with environment-related backgrounds. We also find that this relationship is clearly evidenced when the firm is owned by a lower proportion of foreign investors. Further analysis shows that these directors successfully change their firms to become environmentally friendly. Overall, we conclude that the role of governments in promoting green finance is crucial. The findings of this study may be used as a guideline for decision makers and environmental policymakers to create systems and policies to increase the firm's awareness about the environment in relation to corporate environmental responsibility (CER) ratings of firms

The Impact of Expected and Unexpected Socio-economic Change on Air Pollutants and Carbon

Department of Urban and Environmental Engineering (Disaster Management Engineering)This study investigates the impact of unexpected and expected socio-economic changes on air pollutants and carbon. For the impact of socio-economic changes on air pollutants, the analysis used the air quality, thermal power generation, and macroeconomic indices data to identify the effect of thermal power generation and COVID-19 on air quality. The findings are that thermal power generation had worsened the level of CO from 2015 to 2019 and that the impact of COVID-19 improves the air quality in China and South Korea. For the impact of socio-economic changes on carbon, the analysis used firm-level emissions and corporate variables to identify how ETS implementation has influenced carbon productivity (a firm-level revenue created per unit of carbon emission). The findings are that the firms increased carbon productivity after participating in the national-level Emission Trading Scheme (ETS) of South Korea, especially for high-emitting industries, and firms that are profitable, innovative, and managed by CEOs with environment-related educational or working experience successfully increase their carbon productivity. These findings suggest that to improve air pollution and global warming, governments have to establish appropriate air quality control measures on each air pollutant and assist green-minded firms and firms have to increase profitability and invest in eco-friendly technologies by green-minded executives with regulations on high-emitting firms.ope

Effects of emission trading schemes on corporate carbon productivity and implications for firm-level responses

Since the South Korean government enacted the Emission Trading Scheme (ETS), companies have been striving to simultaneously improve productivity and reduce carbon emissions, which represent conflicting goals. We used firm-level emissions and corporate variables to investigate how ETS enactment has affected carbon productivity, which is a firm-level revenue created per unit of carbon emission. Results showed that firm-level carbon productivity increased significantly under the ETS, and such a trend was more evident for high-emission industries. We also found that companies with high carbon productivity were (1) profitable, (2) innovative, and (3) managed by CEOs with experience in environmental fields. These findings suggest that to achieve the conflicting goals of increasing corporate profits while reducing emissions, firms have to invest in green technologies, and such decisions are supported by green leadership. Our findings also have implications for corporate leadership; data highlight the importance of managing human resources and deploying investment policies to respond to ETS

A Roundabout Approach to Control Morphological Orientation and Solar-Cell Performance by Modulating Side-Chain Branching Position in Benzodithiophene-Based Polymers

To be meaningful to guide the rational design of novel high-performance conjugated semiconductors, we prepared three benzo[1,2-b:4,5-b]dithiophene (BDT)-based polymers by systematically moving the branching point of the alkyl chain. The effect of side-chain engineering was thoroughly investigated by a range of techniques. We demonstrate that a subtle change in the branching position in the BDT core can have a critical impact on polymer packing and preferential backbone orientation in thin films; copolymers made from BDT and thieno[3,4-c]pyrrole-4,6-dione units (TPD) adopt more of a face-on orientation as the branching point is shifted closer to the backbone, which can be correlated with a dramatic difference in solar-cells performance. The high short-circuit current density (11.6 mAcm(-2)) for the copolymer with one carbon atom between the alkoxylated oxygen atom and the branching point results from its predominantly face-on orientation and smoother surface in thin films, which results in power conversion efficiencies as high as 4.56%.clos

Thiophene and Naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole Based Alternating Copolymers for Polymer Solar Cells

Two planar type photovoltaic polymers based on naphthobisthiadiazole, poly(2,5-bis(2-hexyldecyloxy)phenylene-alt-(5,10-dithiophen-2-yl)naphtho [1,2-c :5,6-c]bis [1,2,5]thiadiazole) (h-PPDTNTz) and poly(2,5-bis(2-decyltetradecyloxy)phenylene-alt-(5,10-dithiophen-2-yl)naphtho [1,2-c:5,6-c]bis[1,2,5]thiadiazole) (d-PPDTNTz) were synthesized by incorporating intrachain noncovalent Coulombic interactions in the molecular design. To achieve a delicate balance of molecular weight, solubility as well as bulk film morphology, hexyldecyloxy (h-) and decyltetradecyloxy (d-) side-chains were substituted, which played a decisive role in modulating morphology, film packing structure and macroscopic device properties. Both polymers showed a broad light absorption up to similar to 800 nm and d-PPDTNTz exhibited a deeper HOMO and preferentially face-on orientation in pristine and blended films with PCIIBM. The detailed optical, electrochemical, thermal, morphological and the resulting photovoltaic characteristics were studied. The best power conversion efficiency of similar to 6.7% was measured for d-PPDTNTz:PC71BM, suggesting that the careful choice of side-chains is necessary for fully optimize the photovoltaic materials and devices.clos

A new dithienopyridine-based polymer for an organic electronics

Convergence Technology (RIGET), Gyeongsang National University, Jin-ju, 660-701, Korea Republic of Korea A new dithienopyridine-based copolymer (PDT-TBT) was designed and synthesized. The copolymer showed good solubility in chloroform, chlorobenzene, and dichlorobenzene. The thermogravimetric analysis curve showed that the copolymer had good thermal stability with weight loss of less than 5% at 341 ??C. The UV absorption maximum of the polymer appeared at 550 nm in solution and 600 nm in the film. The HOMO and LUMO of the copolymer were -5.50 eV and -3.63 eV, respectively. The copolymer exhibited the best performance when the PC61BM ratio was 1:2 (w/w %), with a JSC of 3.56 mA/cm2, a VOC of 0.45 V, an FF of 0.27%, and a PCE of 0.43%. A thin film transistor with PDT-TBT as the active layer showed mobility of 5.02??10-3 cm2/Vs, an on/off ratio of 1.19??105 and a threshold voltage of -22.75 V.clos

Mixed solvents for the optimization of morphology in solution-processed, inverted-type perovskite/fullerene hybrid solar cells

We investigate mixed solvents of N,N-dimethylformamide (DMF) and ??-butyrolactone (GBL) to produce the smooth surface of a perovskite film and uniform crystal domains. This ideal morphology from mixed solvents enhances the power conversion efficiency to over 6% by improving the exciton dissociation efficiency and reducing the recombination loss at both interfaces of PEDOT:PSS/perovskite and perovskite/PCBM.close28

Optically Tunable Plasmonic Two-Dimensional Ag Quantum Dot Arrays for Optimal Light Absorption in Polymer Solar Cells

The application of localized surface plasmon resonance (LSPR) phenomena is an effective strategy to enhance the performance of polymer solar cells (PSCs) because of their ability to efficiently scatter light and dramatically increase light absorption in the active layer of PSCs. Unlike previous reports investigating LSPR materials in PSCs, we have.approached the LSPR phenomenon from a physical perspective by examining the influence of the surrounding environment LSPR properties. Uniformly ordered two-dimensional 10 nm Ag quantiun dot arrays (2D Ag-QAs) were prepared and utilized in PSCs. The 2D Ag QAs were incoiliorated into-electron transport layers with different. efractive indices, which showed a significant liathochrornic shift as the, refractive index increased and excellent agreement with theoretical calculations taking intrinsic size effects, nonlocal response, and plasmon, coupling effects into account. When incorporated into PSCs, power conversion efficiencies of op to, 8.51% were realized a 12.5% enhancement compared to devices without Ag QAs