Fully Solution-Processed Copper Chalcopyrite Thin Film Solar Cells: Materials Chemistry, Processing, and Device Physics

Chalcopyrite solar cells have attracted a lot of attention due to their highest power conversion efficiency among all thin film solar cells. However, significant cost reductions as well as large scale production are necessary to compete with conventional electrical power generation. The development of new deposition technologies for the absorber layer as well as the conducting window layer that are compatible with atmospheric deposition on a manufacturing-scale are urgently required to significantly offset production costs. This dissertation demonstrates the development of fully solution-processed high performance CuIn(Se,S)2 photovoltaic devices based on a hydrazine processed absorber layer and metal nanowire composite window layer. Furthermore, the included studies present a deep understanding of the materials chemistry involved in the formation of the CuIn(Se,S)2 precursor molecules and thin films, as well as material design for metal nanowire composite window layers, and the charge transport mechanism in the fully solution-processed high performance CuIn(Se,S)2 photovoltaic devices. Chapter 2 presents the identification of the molecular precursor species present in hydrazine CuIn(Se,S)2 solutions, and precise control of energy band gap of CuIn(Se,S)2 by tailoring the bonding environment of the molecular species present in precursor solutions. Chapter 3 investigates secondary phase formation at the Mo/CuIn(Se,S)2 interface as well as a strategy for achieving a large grained CuIn(Se,S)2 film structure with demonstrated photovoltaic device performance using a sputtered metal oxide window layer. Chapter 4 focuses on the development of transparent conductors composed of solution processed silver nanowires composite window layers demonstrating better optoelectronic and mechanical properties than conventionally sputtered indium tin oxide films. Chapter 5 centers on the complete replacement of sputtered metal oxides by metal nanowires embedded in conductive nanoparticle window layer without any sacrifices in device performance, elucidate the role of each component of the window layers by probing spatially resolved carrier collection, and presents a detailed study of band alignment in fully solution-processed high performance CuIn(Se,S)2 photovoltaic devices by investigating current-voltage characteristics in the dark and under illumination from several controlled wavelength ranges. Thin film chalcopyrite solar cells employing solution-processed absorber layers combined with metal nanowire-metal oxide nanoparticle composite window layers are anticipated to effectively serve as a renewable energy source with reduced fabrication costs and competitive device performance

Data on microstructural and optoelectronic properties of electrodeposited silver mesh transparent conducting electrodes

Electrodeposited Ag mesh transparent conducting electrodes (TCEs) based on self-cracking templates can achieve high optical transmittances and low sheet resistances by controlling the shape of the self-cracking templates and electrodeposition duration. The surface coverage of the mesh is mainly determined by the surface shape of the self-cracking template. Electrodeposition of Ag can adjust the thickness of the mesh, significantly reducing the sheet resistance while maintaining the high optical transmittance of the TCEs. The TCE electrodeposited for 30 s exhibited an optical transmittance as high as 88.4% and a sheet resistance as low as 2.24 Ω/□. Here we provide the microstructural and optoelectronic performance data of the electrodeposited Ag mesh TCEs

Microstructures and Oxidation Behavior According to Nb:Mo Ratio in a Nb–Mo–Si System with Si Pack Cementation Coatings

Research is being conducted on Mo- and Nb-based alloys that are used in the aerospace sector, including those used for advanced gas turbines and aircraft engines. There is a limit to using Mo, which has a high density among refractory metals, and a few studies exist describing the addition of Nb to Mo–silicide alloys. There is a lack of guidance research on the basic Nb:Mo ratio of alloys, and it is necessary to study how to improve oxidation resistance. Therefore, this study aims to improve oxidation resistance by controlling the ratio of Nb and Mo in (Nbx, Moy)Si2 coating layers with Si pack cementation coatings on Nb–Mo alloys. Static oxidation tests were carried out at 1200 °C for 6 h to confirm the oxidation characteristics. As a result, a SiO2 or SiO2 + Nb2O5 ceramic protective layer was formed on the surface. After the oxidation tests, alloys with a Nb content of less than 35 at.% were found to protect the surface. The ratios of Nb and Mo in the Nb–Mo alloy and silicide coating layer were compared, and the improvement of oxidation resistance is discussed in terms of microstructural evolution

Additional file 1: Figure S1. of Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition

45° tilted SEM image of InP nanowires on InP(111)B substrate grown at 365 °C for 300 s using TMIn (5.0 × 10−5 mol/s) and TBP (7.4 × 10−6 mol/s) precursors with the molar ratio of V/III = 29. Mechanically exfoliated InP nanowires are used as the reference for Raman spectroscopy measurements. (PNG 215 kb

Efficient white organic light emission by single emitting layer

Stable organic white light-emitting diodes are successfully fabricated by a single organic white emitting layer, which is Bis (2-methyl-8-quinolinato) (triphenylsiloxy) aluminum (III) (SAlq) doped red fluorescent dye of 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). The incomplete energy transfer from blue-emitting SAlq to red-emitting DCJTB enables to obtain a stable white balanced light-emission by the DCJTB doping concentration of 0.5%. A device with the structure of ITO/TPD (50 nm)/SAlq:DCJTB (30 nm, 0.5%)/Alq3 (20 nm)/LiF (0.5 nm)/Al (110 nm) shows maximum luminance of 20 400 cd/m2 at 810 mA/cm2, external quantum efficiency of 2% at 200 cd/m2 (3 mA/cm2), power efficiency of 2.3 lm/W at 67 cd/m2 (1 mA/cm2), and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.34, 0.39) at 1.8 mA/cm2 to (0.31, 0.38) at 36 mA/cm2

Suppressed Formation of Conductive Phases in One-Pot Electrodeposited CuInSe₂ by Tuning Se Concentration in Aqueous Electrolyte

The single-bath electrochemical deposition of CuInSe₂ often leads to short-circuit behavior of the resulting solar cells due to the high shunt conductance. In this study, in an attempt to resolve this problem, the influence of the Se precursor concentration (<i>C</i>_Se) on electrodeposited CuInSe₂ films and solar cell devices is examined in the <i>C</i>_Se range of 4.8 to 12.0 mM in selenite-based aqueous solutions containing Cu and In chlorides along with sulfamic acid (H₃NSO₃) and potassium hydrogen phthalate (C₈H₅KO₄) additives. As <i>C</i>_Se increases, the CuInSe₂ layers become porous, and the grain growth of the CuInSe₂ phase is restricted, while the parasitic shunting problem was markedly alleviated, as unambiguously demonstrated by measurements of the local current distribution. Due to these ambivalent influences, an optimal value of <i>C</i>_Se that achieves the best quality of the films for high-efficiency solar cells is identified. Thus, the device prepared with 5.2 mM Se exhibits a power-conversion efficiency exceeding 10% with greatly improved device parameters, such as the shunt conductance and the reverse saturation current. The rationale of the present approach along with the physicochemical origin of its conspicuous impact on the resulting devices is discussed in conjunction with the electro-crystallization mechanism of the CuInSe₂ compound