Polymer/Metal/Dielectric Electrode for Organic Solar Cells

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Polymer-related transparent electrodes for flexible photovoltaics

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Top-illuminated flexible organic solar cells on opaque substrates

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Design of Nanostructured Optical Layers for Efficient Light Trapping

DoctorThis thesis explores ways to design of nanostructured optical layers for efficient light trapping in organic solar cells (OSCs). OSCs have much attention for realizing next-generation photovoltaics, because of their full potential as solution printing, lightweight, flexibility and low-cost. However, incommensurate absorption length (~100 nm) and exciton diffusion length (~10 nm) of organic materials have remained a major issue to enhance the power conversion efficiency (PCE) in OSCs. One way to improve light trapping is to employ the various nanostructures, which can change behavior of light in thin optical layers. However, the maximum achievable absorption and optimal nanostructures are still open questions. The work in this thesis focuses on design of novel optical layers, optimization of nanostructures, and theoretical analysis with aim of efficient light trapping in OSCs. In the first part of thesis (chapter 1, 2 and 3), I introduce the basic concepts of OSCs and research trends of light trapping technology for highly efficient OSCs. Fundamental optical modeling tools are presented including characteristic matrix method and rigorous coupled wave analysis. In chapter 4 and 5, I propose the novel structure of polymer/metal/dielectric (PMD) and dielectric/metal/polymer (DMP) as transparent conducting electrodes. Even though the dielectric/metal/dielectric (DMD) multilayer was successfully employed as a transparent electrode in optoelectronic devices, there are some drawbacks such as dewetting of thin metal layer, peak transparency at specific dielectric thickness, and planar structure by physical deposition. In this research, I find that the transmittance insensitive to the thickness could be achieved by empolying the low refractive index of polymer. It brings about excellent transparency without absorption loss even in nanostructured PMDor DMP layers. Also well-ordered nanopatterns can be easily adopted to electrodes becaus of easy structuring and excelleng flexibility of soft materials. In chapter 6, I demonstrate wavelength-scale structures of inverted hexagonal-pyramid on polymer as a haze film for broadband and omnidirectional light harvesting in OSCs. Subwavelength-scale structures have discovered unique antireflection properties in broad solar spectral range. However, the reflectance decreases by only 2 ~ 4%, which could not guarantee effectively enhanced PCE in OSCs. In this research, I have introduced a powerful design for effective light trapping using a wavelength-scale structured films. Through the calculation of devices with different geometry of structures, we identify the roles of wavelength-scale structures in light trapping. In chapter 7, I demonstrate branch shape of indium thin oxide (ITO) nanostructures as an antireflection layers in application to organic solar cells. The three-dimensional ITO nanobranches can be easily fabricated on the front side of glass using a one-step and scalable approach based on electron beam deposition. The optimized structures exhibited excellent broadband antireflection properties in the visible wavelength region

A challenge beyond bottom cells: Nanostructured dielectric/metal/polymer (DMP) electrodes for top-illuminated flexible organic solar cells on opaque substrates

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Polymer/Metal/Dielectric <P/M/D> Transparent Electrode for Organic Solar Cell

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Felxible transparent organic/Ag/metal oxide electrode for organic solar cell

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플렉서블한 유기태양전지의 브로드밴드한 투과도를 지닌 전극 구조 설계

MasterBroadband transparent electrodes, Ta2O5/Ag/WO3-x, are successfully designed to enhance light absorption and carrier transport properties in organic solar cells (OSCs) as an alternative to ITO/PEDOT:PSS. Employing the optical constants matching layer, zero reflection condition could be achieved over a broad range of wavelengths. Moreover, the non-stoichiometric WO3-x could induce a large density of gap states near the Fermi level via quick thermal deposition, acting as carrier transport path. Significantly improved current densities were achieved, increasing the power conversion efficiency from 2.1 % to 2.9 % which values are comparable to conventional ITO device

Efficiency top illuminated polymer solar cells with distributed bragg reflector on flexible metal substrate

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Design considerations for alternative transparent electrode of DMD multilayer for organic photovoltaics

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