Download or read book Investigation of Charge Carrier Dynamics in Novel Photovoltaic Materials written by Hannes Hempel and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charge Carrier Dynamics in Photovoltaic Materials written by and published by . This book was released on 2014 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: "We employ the experimental technique THz Time Domain spectroscopy (THz-TDS) to study the optoelectronic properties of potential photovoltaic materials. This all-optical method is useful for probing photoconductivities in a range of materials on ultrafast timescales without the application of physical contacts. Using this technique we study the process of carrier multiplication (CM) - the excitation of multiple charge carriers by a single photon - in indium nitride (InN). InN possesses a number of properties favorable for efficient CM. However, we find that CM in InN is rather inefficient, contributing only to a modest efficiency increase in a potential InN based solar cell. Additionally, we study the dynamics of photoexcited carriers in 2-dimensional graphene with emphasis on the process of multiple hot carrier generation, which is related to carrier multiplication. A very efficient energy transfer from an optically excited charge carrier into multiple hot carriers is shown. We also perform a study of the photoconductivity of two types of 1-dimensional graphene-based semiconductors, flat graphene nanoribbons and carbon nanotubes. Free charge carriers are observed immediately after excitation. The mobility of these carriers is found to vary significantly for the different types of 1-D conductors. The applicability of these graphene based conductors in organic solar cell architectures is briefly discussed. Finally, we explore the carrier transport properties of colloidal TiO2 films commonly used in dye- and quantum dot sensitized solar cells. We find that the photoresponse is dominated by long percolation pathways of connected particles, responsible for the materials long range conductivity."--Samenvatting auteur.

Download or read book Charge Carrier Dynamics in Novel Solar Materials written by and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigating Carrier Dynamics in Photovoltaic Materials written by Mohammad Mehdi Taheri and published by . This book was released on 2021 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding photoexcited carrier dynamics is crucial for designing high-performance optoelectronic devices. Carrier cooling in semiconductors, charge transfer across interfaces, and recombination mechanisms are critical processes in photophysical systems that typically occur on the time scale of less than a picosecond to several nanoseconds. Ultrafast techniques, including ultraviolet-visible-infrared transient absorption (TA), time-resolved terahertz spectroscopy (TRTS), and time-resolved photoluminescence (TRPL), are ideal tools for studying charge carrier dynamics at such timescales. This thesis will focus on the application of complementary spectroscopy techniques and modeling to investigate carrier dynamics within CdSe/CdS core/shell colloidal quantum dots (QDs) and Cu3AsS4 and CdTe thin films.CdTe solar technology has attracted the photovoltaic (PV) community for the past three decades owing to its low production cost and record efficiency of 22.1%. However, some challenges must be overcome to further improve its efficiency to the 25% range. Cu3AsS4 thin film is a promising emerging candidate as a PV absorber material due to its earth-abundant and nontoxic constituent elements, but its optoelectronic properties are not well known. Carrier dynamics reveal important details about the recombination processes that limit PV performance. Improvements in the PV device efficiency require a full understanding of the routes for carrier recombination processes.TRPL, which measures emission, has conventionally been used to evaluate recombination mechanisms in thin film PVs, but carrier redistribution often dominates the response at short times. Here we report on the quantification of carrier dynamics and recombination mechanisms by complementary use of both TRTS, which measures photoconductivity, and TRPL combined with numerical modeling of the continuity equations and Poisson's equation. We were able to distinguish and quantify bulk and surface recombination in CdTe and Cu3AsS4 thin films, which is critical for the development of thin film PVs with higher efficiency.We also investigated the carrier dynamics in functionalized CdSe/CdS core/shell QDs using complementary ultrafast TA and TRPL spectroscopies and kinetic modeling. Cd-chalcogenide QDs have been widely studied because of their excellent optical properties and their facile tunability. The Cd-chalcogenide QDs have been studied for more than 20 years, but the ambiguities in the interpretation of the TA spectra are still under debate. For one thing, the photoexcited TA signal in Cd-chalcogenide QDs has been fully attributed to conduction band electrons, neglecting any contributions from valence band holes. In this work, we present a comprehensive picture of the electronic processes in photoexcited CdSe/CdS core/shell QDs. We have demonstrated through complementary spectroscopic experiments and kinetic modeling that holes affect the TA results and can contribute ~ 30% to the visible range and ~ 72% to the mid-IR range. The comprehensive picture of photophysical processes provided by the complementary ultrafast techniques and kinetic modeling in this work can accelerate both the fundamental science and application development of nanostructured and molecular systems.This thesis will focus on the application of spectroscopy techniques and modeling to investigate carrier dynamics in optoelectronic systems including thin film PVs and colloidal CdSe based QDs. The methodologies presented in this thesis can serve as a guideline for the accurate interpretation of spectroscopic measurements not only for the cases studied here but also for other optoelectronic systems.

Download or read book Optical Investigation of Charge Carrier Dynamics in Organic Semiconductors and Graphene for Photovoltaic Applications written by Karl Matthias Handloser and published by . This book was released on 2014 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charge Carrier Dynamics on Photoelectrode Materials for Solar Energy Conversion written by Lisa Grad and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigating Ultrafast Carrier Dynamics in Perovskite Solar Cells with an Extended conjugated Polymeric Diketopyrrolopyrrole Layer for Hole Transportation written by and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we show a new diketopyrrole based polymeric hole-transport material (PBDTP-DTDPP, (poly[[2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4- c ]pyrrole-1,4-diyl]- alt -[[2,2′-(4,8-bis(4-ethylhexyl-1-phenyl)-benzo[1,2- b :4,5- b ′]dithiophene)bis-thieno[3,2- b ]thiophen]-5,5′-diyl]])) for application in perovskite solar cells. The material performance was tested in a solar cell with an optimized configuration, FTO/SnO 2 /perovskite/PBDTP-DTDPP/Au, and the device showed a power conversion efficiency of 14.78%. The device charge carrier dynamics were investigated using transient absorption spectroscopy. The charge separation and recombination kinetics were determined in a device with PBDTP-DTDPP and the obtained results were compared to a reference device. We find that PBDTP-DTDPP enables similar charge separation time (

Download or read book Lead Halide Perovskite Solar Cells written by David J. Fisher and published by Materials Research Forum LLC. This book was released on 2020-06-05 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lead halide perovskite materials have a huge potential in solar cell technology. They offer the combined advantages of low-cost preparation and high power-conversion efficiency. The present review focusses on the following topics: Power Conversion Efficiency; Electron Transport, Hole Transport and Interface Layers; Material Preparation; Cesium-Doped Lead-Halide Perovskites; Formamidinium-Doped Lead-Halide Perovskites; Methylammonium Lead-Halide Perovskites; Hysteresis, Stability and Toxicity Problems. The book references 334 original resources and includes their direct web link for in-depth reading. Keywords: Solar Cells, Lead Halide Perovskite Materials, Cesium-Doped Lead-Halide Perovskites, Formamidinium-Doped Lead-Halide Perovskites, Methylammonium Lead-Halide Perovskites, Electron-Transport Layer, Hole-Transport Layer, Interface Layers, Hysteresis Problem, Stability Problem, Toxicity Problem.

Download or read book Transient Spectroscopic Studies of Charge Carrier Dynamics in Organic Solar Cells written by Yifan Dong and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lead Halide Perovskite Solar Cells written by Fisher, D.J. and published by Materials Research Forum LLC. This book was released on 2020-06-06 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lead halide perovskite materials have a huge potential in solar cell technology. They offer the combined advantages of low-cost preparation and high power-conversion efficiency. The present review focusses on the following topics: Power Conversion Efficiency; Electron Transport, Hole Transport and Interface Layers; Material Preparation; Cesium-Doped Lead-Halide Perovskites; Formamidinium-Doped Lead-Halide Perovskites; Methylammonium Lead-Halide Perovskites; Hysteresis, Stability and Toxicity Problems. The book references 334 original resources and includes their direct web link for in-depth reading. Keywords: Solar Cells, Lead Halide Perovskite Materials, Cesium-Doped Lead-Halide Perovskites, Formamidinium-Doped Lead-Halide Perovskites, Methylammonium Lead-Halide Perovskites, Electron-Transport Layer, Hole-Transport Layer, Interface Layers, Hysteresis Problem, Stability Problem, Toxicity Problem.

Download or read book Investigation of Charge transfer Dynamics in Organic Materials for Solar Cells written by Christian T. Weisspfennig and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charge Carrier Dynamics in Thin Film Solar Cells written by Christian Strothkämper and published by . This book was released on 2013 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Charge Transport in Organic Photovoltaic Materials Using Lateral Device Structures written by Oleksiy Viktor Slobodyan and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding of charge carrier transport and recombination in bulk heterojunction (BHJ) materials is important for continued improvement of organic photovoltaics (OPVs). Solar cell efficiencies now approach 12% and answers to lingering questions create a roadmap for increasing this value. OPVs are made as vertical structures and majority of analyses in literature are directed to this structure. In this dissertation, theoretical and experimental analyses of lateral devices are developed to compliment the knowledge base established with vertical devices. Lateral OPVs offer unique insights into transport and recombination physics in BHJs: they decouple charge extraction from charge photogeneration, allow clear formation of space-charge regions and recombination zone, open the BHJ to probing, and allow comparison of ambipolar to unipolar electron & hole currents. Lateral OPVs are simulated to understand their current-voltage behavior and link it to development of space-charge. Modeling focuses on the intermediate 3um channel length. At this transport length effects of space-charge behavior are clearly present and all photogenerated charge can be extracted. Modeling work is used to support analysis of experimental results. BHJs made of electron-transporter [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and hole transporting polymer poly[3-hexylthiophene-2,5-diyl] (P3HT) and co-polymer poly[2-(5-(4,4-dioctyl-4H-silolo[3,2-b:4,5-b']dithiophen-2-yl)-3-tetradecylthiophen-2-yl)-5-(3-tetradecylthiophen-2-yl)thiazolo[5,4-d]thiazole] (PDTSi-TzTz) are studied. Transport in PDTSi-TzTz:PCBM is analyzed by profiling the channel potential. The channel potential and current-voltage measurements are used to obtain carrier mobilities and recombination rates. High charge collection efficiency is found even at transport lengths greater than 1 micron. Photocurrent and extracted unipolar injection currents in P3HT:PCBM blends are studied. These measurements yield intensity-dependent mobilities of both electrons and holes. Extraction of both mobility values in the same BHJ point to electron mobility as the limiting factor in OPV performance.

Download or read book Charge Carrier Dynamics in CuInS2 based Solar Cells written by Joris Petrus Theodorus Hofhuis and published by . This book was released on 2009 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation and Control of Ultrafast Charge Carrier Dynamics in Two dimensional Materials and Hybrids written by Shuai Fu and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells written by Michael Edley and published by . This book was released on 2016 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic energy is a clean and renewable source of electricity; however, it faces resistance to widespread use due to cost. Nanostructuring decouples constraints related to light absorption and charge separation, potentially reducing cost by allowing a wider variety of processing techniques and materials to be used. However, the large interfacial areas also cause an increased dark current which negatively affects cell efficiency. This work focuses on extremely thin absorber (ETA) solar cells that used a ZnO nanowire array as a scaffold for an extremely thin CdSe absorber layer. Photoexcited electrons generated in the CdSe absorber are transferred to the ZnO layer, while photogenerated holes are transferred to the liquid electrolyte. The transfer of photoexcited carriers to their transport layer competes with bulk recombination in the absorber layer. After charge separation, transport of charge carriers to their respective contacts must occur faster than interfacial recombination for efficient collection. Charge separation and collection depend sensitively on the dimensions of the materials as well as their interfaces. We demonstrated that an optimal absorber thickness can balance light absorption and charge separation. By treating the ZnO/CdSe interface with a CdS buffer layer, we were able to improve the Voc and fill factor, increasing the ETA cell's efficiency from 0.53% to 1.34%, which is higher than that achievable using planar films of the same material. We have gained additional insight into designing ETA cells through the use of dynamic measurements. Ultrafast transient absorption spectroscopy revealed that characteristic times for electron injection from CdSe to ZnO are less than 1 ps. Electron injection is rapid compared to the 2 ns bulk lifetime in CdSe. Optoelectronic measurements such as transient photocurrent/photovoltage and electrochemical impedance spectroscopy were applied to study the processes of charge transport and interfacial recombination. With these techniques, the extension of the depletion layer from CdSe into ZnO was determined to be vital to suppression of interfacial recombination. However, depletion of the ZnO also restricted the effective diffusion core for electrons and slowed their transport. Thus, materials and geometries should be chosen to allow for a depletion layer that suppresses interfacial recombination without impeding electron transport to the point that it is detrimental to cell performance. Thin film solar cells are another promising technology that can reduce costs by relaxing material processing requirements. CuInxGa(1-x)Se (CIGS) is a well studied thin film solar cell material that has achieved good efficiencies of 22.6%. However, use of rare elements raise concerns over the use of CIGS for global power production. CuSbS2 shares chemistry with CuInSe2 and also presents desirable properties for thin film absorbers such as optimal band gap (1.5 eV), high absorption coefficient, and Earth-abundant and non-toxic elements. Despite the promise of CuSbS2, direct characterization of the material for solar cell application is scarce in the literature. CuSbS2 nanoplates were synthesized by a colloidal hot-injection method at 220 ℗ʻC in oleylamine. The CuSbS2 platelets synthesized for 30 minutes had dimensions of 300 nm by 400 nm with a thickness of 50 nm and were capped with the insulating oleylamine synthesis ligand. The oleylamine synthesis ligand provides control over nanocrystal growth but is detrimental to intercrystal charge transport that is necessary for optoelectronic device applications. Solid-state and solution phase ligand exchange of oleylamine with S2- were used to fabricate mesoporous films of CuSbS2 nanoplates for application in solar cells. Exchange of the synthesis ligand with S2- resulted in a two order of magnitude increase in 4-point probe conductivity. Photoexcited carrier lifetimes of 1.4 ns were measured by time-resolved terahertz spectroscopy, indicating potential for CuSbS2 as a solar cell absorber material.

Download or read book Spectroscopic Studies on the Impact of Defects in Hybrid Organic inorganic Perovskites on Charge Carrier Dynamics and Photovoltaic Device Performance written by Timothy Philippe Pollock and published by . This book was released on 2020 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic devices based on hybrid organic-inorganic perovskites have seen a historic rise in efficiency over the past decade. Relatively low cost of fabrication has allowed a wide range researchers to make meaningful contributions. This class of materials is fascinating in that it acts in some ways like well-known semiconductor systems, but exhibits certain key differences, which provides ample opportunity for future fundamental studies. The work described in this dissertation includes the spectroscopic characterization of charge carriers in methylammonium lead iodide and the use of this characterization, along with time-resolved spectroscopy, to better understand the influence of carrier dynamics on solar cell device performance. We observed that a decrease in device fill factor corresponded to an increase in trap state density and a change in the trapping rate constant, implying that the different film fabrication methods lead to a change in the nature of the trap states present in the film. Delving further into understanding the influence of trap states on the excited state dynamics in this system, we performed pump-push-probe spectroscopy and transient absorption spectroscopy with a variable wavelength sub-gap pump pulse to study both the energetics and kinetics of trapping processes in methylammonium lead iodide films. Here we utilized a low energy push pulse to delocalize trapped electrons back into the conduction band and then modeled the resulting recombination based on changes in trapped and free electron densities. From these studies, we were able to add experimental observations to the body of knowledge on the electronic structure of hybrid organic-inorganic perovskites. We also showed how dynamics in the early time periods (ps-ns) following photoexcitation can influence perovskite solar cell performance.