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 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 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 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 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 Ultrafast Carrier Dynamics at P n Junction of Cu In Ga Se2 Based Solar Cells Measured by Optical Pump Terahertz Probe Spectroscopy written by Woo-Jung Lee and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Among other materials, the p-type Cu(In,Ga)Se2 (CIGS) alloy has attracted attention as the most efficient absorber in thin-film solar cells. The typical CIGS layer is deposited with a polycrystalline structure containing an amount of native defect states, which serve as carrier traps and recombination centers. These defect states in the CIGS layer can be easily changed after deposition of an n-type buffer layer, due to the formation of p-n junctions. To understand the influence of the p-n junction on these defect states, the behavior of photoexcited carriers, from the CIGS absorber to the buffer layer, is considered to be an important issue and is closely related to solar cell performance. In this study, we performed experiments to investigate the ultrafast carrier dynamics of CIGS-based solar cells, using optical pump terahertz (THz) probe (OPTP) spectroscopy, and demonstrated the correlation between solar cell performance and the behavior of photoexcited carrier dynamics.

Download or read book State of the Art Program on Compound Semiconductors 58 SOTAPOCS 58 written by J. H. He and published by The Electrochemical Society. This book was released on 2015 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigating Device Physics in Bulk heterojunction Organic Solar Cells Through Materials Engineering of Interfaces written by Kevin M. O'Malley and published by . This book was released on 2013 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have designed and implemented several organic photovoltaic materials with the goal of engineering interfaces within bulk-heterojunction organic solar cells. In one project, we synthesized a C60 bis-adduct surfactant for use as a buffer layer between the photoactive layer and the thermally evaporated metal top contact of conventional structure, bulk-heterojunction organic solar cells. By systematically varying the work function of the contact metal, with and without the surfactant buffer layer, we gained insight into the physics governing the photoactive layer/metal interface and vastly improved the device performance. By applying Mott-Schottky analysis to the capacitance-voltage data obtained for these devices we were able to conclude that the surfactant modifies the metal work function to an appreciable extent, and allows for efficient charge extraction and significantly enhanced open-circuit voltage regardless of the chosen contact metal. This enhancement allowed us to use more air-stable metals that would ordinarily be prohibited due to suboptimal energy level alignment at the electron-collecting electrode. In a second line of investigation, we used impedance spectroscopy to probe the charge carrier recombination dynamics and their effects on device performance in organic solar cells composed of poly(indacenodithiophene-co-phananthrene-quinoxaline), as well as its fluorinated derivatives, and various fullerenes. We find that the morphology of the blended photoactive layer has a strong influence on the electronic density-of-states distribution, which in turn directly affects the recombination rate as well as the achievable open-circuit voltage. We show that attempting to increase the open-circuit voltage through structurally tuning the energy levels of polymer and fullerene inadvertently introduces different bulk phase separation that leads to a reduction in photocurrent. We observe that the recombination lifetime decreases more dramatically with increasing excess photogenerated charge carrier density for blends with more finely separated phases and propose that the resulting increase in recombination surface area leads directly to reduced overall device performance, despite a marked increase in open-circuit voltage.

Download or read book Defects and Charge carrier Lifetime in Early stage Photovoltaic Materials written by Jeremy Roger Poindexter and published by . This book was released on 2018 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: To minimize risks associated with climate change, we must rapidly reduce greenhouse gas emissions worldwide by shifting reliance away from fossil fuels. Solar photovoltaic (PV) modules are well suited for reducing emissions; however, manufacturing and capital costs must continue to decline for rapid, worldwide PV adoption. Low-cost and Earth-abundant “thin film” materials offer potential in spurring PV growth, but their development is often hampered by the presence of defects, which degrade solar cell efficiency due to short charge-carrier lifetimes. In this thesis, such defects and their impact on lifetime in early-stage PV materials are investigated, focusing on experimental methods to assess lifetime connected to theoretical concepts about both defects and lifetime measurements themselves. First, time-resolved photoluminescence is performed, and both analytical and numerical modeling are used to determine lifetimes exceeding 1 nanosecond in six materials predicted to be “defect tolerant.” Two-photon spectroscopy is then employed to decrease the effect of surface recombination, enabling more representative estimates of “bulk” lifetime. Second, the role of impurities is explored by intentionally contaminating lead halide perovskites with iron. Synchrotron-based X-ray techniques are also utilized to investigate the distribution and charge state of incorporated iron, and perovskite solar cells are found to tolerate approximately 100 times more iron in the feedstock than comparable p-type silicon solar cells. In addition, improved methods for extracting lifetime from solar cell devices are explored. Quantum efficiency measurements are performed and modeled on tin monosulfide solar cells to verify that very short lifetimes (30–100 picoseconds) limit device performance. Furthermore, temperature- and illumination-dependent current–voltage measurements are performed and modeled in iron-contaminated silicon solar cells- and analyzed with the help of a Bayesian inference algorithm-to estimate the defect parameters that directly relate to lifetime. Collectively, these studies serve to provide a more robust framework for assessing and mitigating the presence of defects in early-stage PV materials, streamlining efforts to better optimize their photovoltaic performance.

Download or read book Investigation of Sub granular Dynamics in Halide Perovskites Via Atomic Force Microscopy written by Mehmet Yenal Yalcinkaya and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Halide perovskites are considered as next generation solar cell absorbers due to their several advantages over conventional solar cell absorber materials such as adjustable bandgap, high photoluminescence (PL) quantum yield, low charge recombination rate, long charge diffusion length, and defect tolerance. However, perovskite photovoltaic devices suffer from power conversion losses at interfaces. Therefore, understanding the local features and charge carrier dynamics at interfaces is crucial, making macroscopic measurements inefficient for this purpose. Among the microscopic techniques, optical microscopy and its derivatives, such as PL microscopy, are the most common ones. However, they suffer from the diffraction limit, resulting in low-resolution imaging. In this work, I focused on studying local features in halide perovskite films and devices at internal interfaces, such as grain boundaries and ferroelastic twin domains, or external interfaces in devices where two components of a perovskite-based device meet. Here, atomic force microscopy (AFM) comes into play. To understand the nanoscale properties of perovskite interfaces, I used electrical AFM modes such as piezoresponse force microscopy (PFM), conductive AFM (C-AFM), and Kelvin probe force microscopy (KPFM). First, I investigated the strain properties in halide perovskites by monitoring ferroelastic twin domains via PFM and x-ray diffraction (XRD). I introduced strain to halide perovskite films by changing the precursor solution. PFM measurements showed altered twin domain patterns that are correlated with strain changes within films. I used XRD measurements to support my claim for a change in overall strain and twinning behavior in the films. My investigation revealed that any chemical gradient in halide perovskites leads to a strain gradient as well. Furthermore, I investigated the local charge carrier dynamics and conductivity at halide perovskite grains and grain boundaries via time-resolved KPFM and C-AFM. Photoconductivity and photovoltage maps I obtained suggest that grain boundaries are high-defect areas that promote faster electron-hole recombination and ion migration. Furthermore, the behavior of charge carriers at grain boundaries changes when grain size changes. Ultimately, this work shows how sub-granular features and device interfaces affect charge carrier dynamics in halide perovskite devices. Therefore, this work may contribute to the optimization of halide perovskite devices for commercialized use.

Download or read book Halide Perovskites written by Tze-Chien Sum and published by John Wiley & Sons. This book was released on 2019-03-25 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Real insight from leading experts in the field into the causes of the unique photovoltaic performance of perovskite solar cells, describing the fundamentals of perovskite materials and device architectures. The authors cover materials research and development, device fabrication and engineering methodologies, as well as current knowledge extending beyond perovskite photovoltaics, such as the novel spin physics and multiferroic properties of this family of materials. Aimed at a better and clearer understanding of the latest developments in the hybrid perovskite field, this is a must-have for material scientists, chemists, physicists and engineers entering or already working in this booming field.

Download or read book Advances in Fabrication and Investigation of Nanomaterials for Industrial Applications written by Sivashankar Krishnamoorthy and published by Springer Nature. This book was released on with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Perovskite Materials written by Likun Pan and published by BoD – Books on Demand. This book was released on 2016-02-03 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book summarizes the current state of the know-how in the field of perovskite materials: synthesis, characterization, properties, and applications. Most chapters include a review on the actual knowledge and cutting-edge research results. Thus, this book is an essential source of reference for scientists with research fields in energy, physics, chemistry and materials. It is also a suitable reading material for graduate students.

Download or read book Academic Earmarks written by United States. Congress. House. Committee on Science, Space, and Technology and published by . This book was released on 1995 with total page 850 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Emerging Photovoltaic Materials written by Santosh K. Kurinec and published by John Wiley & Sons. This book was released on 2018-11-30 with total page 827 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the recent advances in photovoltaics materials and their innovative applications. Many materials science problems are encountered in understanding existing solar cells and the development of more efficient, less costly, and more stable cells. This important and timely book provides a historical overview, but concentrates primarily on the exciting developments in the last decade. It includes organic and perovskite solar cells, photovoltaics in ferroelectric materials, organic-inorganic hybrid perovskite, materials with improved photovoltaic efficiencies as well as the full range of semiconductor materials for solar-to-electricity conversion, from crystalline silicon and amorphous silicon to cadmium telluride, copper indium gallium sulfide selenides, dye sensitized solar cells, organic solar cells, and environmentally-friendly copper zinc tin sulfide selenides.

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 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: