Organic-inorganic hybrid solar cells such as dye-sensitized solar cells (DSSCs) have reached photovoltaic conversion efficiency of 12.3%.1 Their immediate successor, perovskite solar cells (PSCs), have reached an unprecedented efficiency of 17.9% in 2014, from 3.81% in 2009 2, making them competitive with thin-film silicon based PV technology. However, the most significant concern for the organic-inorganic solar cells is their long-term instability, especially at high temperature, above ca. 60 °C, and in contact with moisture present in the air. Their application will be limited unless they have credited stability performance. Improving the stability of organic-inorganic solar cells and understanding their degradation mechanisms is essential for their commercialization and wide-spread use. In the thesis, the stability and degradation mechanisms of two types of organic-inorganic solar cells: flexible dye-sensitized solar cells (DSSCs) built on ITO/PEN substrates and perovskite solar cells (PSCs) were investigated.The first chapter was a general introduction to the organic-inorganic hybrid solar cells, especially dye-sensitized solar cells and perovskite solar cells, such as the development history, structure and operating principles of the cells and the research objectives of the studies.In Chapter 2, literatures regarding the stability of DSSCs and PSCs were thoroughly reviewed and findings of their degradation mechanisms were summarized, which also pointed out research gaps and critical stability issues that still need to be understood and improved.In Chapter 3, all the experimental details are specified, including the chemicals, materials, device fabrication and characterization techniques, stability testing conditions and data analysis. In Chapter 4, the characteristics of flexible DSSCs with the photoanode produced using cold isostatic pressing technique were studied using electrochemical impedance spectroscopy (EIS). The data obtained were analyzed using a transmission line model of DSSCs, which pointed out that the pressing technique may improve short term performance of the devices, but the long-term performance of devices made on plastic substrates deteriorated with aging as a result of reduced TiO2 particle-particle and/or particle-conductive substrate contacts.The results obtained from Chapter 4 gave rise to the inspiration of the studies in Chapter 5, where the mechanical and electrochemical stability of compressed photoanodes (TiO2/ITO/PEN) and counter electrodes (Pt/ITO/PEN) in three different ionic liquid (IL) based electrolyte environment were studied using mechanical bending machine, cyclic voltammetry (CV), EIS, X-ray photoelectron spectroscopy and Inductively coupled plasma mass spectrometry. The results showed that the presence of Li+ ions and H2O molecules in the electrolyte were detrimental to the stability of devices. Li+ ions were responsible to the detachment of Pt particles from the Pt/ITO/PEN electrode and the increase in the recombination resistance of compressed TiO2 films, explaining the gradual increase of Voc with aging observed in chapter 4. The presence of water molecules in the electrolyte can cause degradation of the electrolyte species, forming iodate compounds, and also serious degradation of the ITO substrate. The most stable outcome could be obtained with Li+ ions and H20 free electrolyte. Efficient and stable flexible DSSCs that take advantage of the negligible vapor pressure of IL electrolytes, with minimal sacrifice of photovoltaic conversion efficiency, were successfully produced and demonstrated in Chapter 6 using an ALD deposited blocking layer of 12 nm and an around 1 μm thick TiO2 film, sensitized with hydrophobic dye (MK-2).Following the success of making more stable DSSCs, a much improved stability of the perovskite solar cells was demonstrated in Chapter 7 by using a sophisticated sealing method that effectively reduced the attack of water from the environment. The cells showed outstanding stability at 50% humidity and one sun illumination over 16 temperature cycling tests (350 hours) at cell temperatures of 10 to 100 °C, followed by 500 hours constant cell temperature testing at 85 °C. Also, the degradation mechanisms were revealed using post-mortem analysis of these cells using XRD and cross-sectional SEM analysis.We drew some final conclusions in Chapter 8 together with our outlooks in the future research and development of more stable DSSCs and PSCs.

Organic solar cells have emerged as new promising photovoltaic devices due to their potential applications in large area, printable and flexible solar panels. Organic Solar Cells: Materials and Device Physics offers an updated review on the topics covering the synthesis, properties and applications of new materials for various critical roles in devices from electrodes, interface and carrier transport materials, to the active layer composed of donors and acceptors. Addressing the important device physics issues of carrier and exciton dynamics and interface stability and novel light trapping structures, the potential for hybrid organic solar cells to provide high efficiency solar cells is examined and discussed in detail. Specific chapters covers key areas including: Latest research and designs for highly effective polymer donors/acceptors and interface materials Synthesis and application of highly transparent and conductive graphene Exciton and charge dynamics for in-depth understanding of the mechanism underlying organic solar cells. New potentials and emerging functionalities of plasmonic effects in OSCs Interface Degradation Mechanisms in organic photovoltaics improving the entire device lifetime Device architecture and operation mechanism of organic/ inorganic hybrid solar cells for next generation of high performance photovoltaics This reference can be practically and theoretically applied by senior undergraduates, postgraduates, engineers, scientists, researchers, and project managers with some fundamental knowledge in organic and inorganic semiconductor materials or devices.

Comprehensive Guide on Organic and Inorganic Solar Cells: Fundamental Concepts to Fabrication Methods is a one-stop, authoritative resource on all types of inorganic, organic and hybrid solar cells, including their theoretical background and the practical knowledge required for fabrication. With chapters rigorously dedicated to a particular type of solar cell, each subchapter takes a detailed look at synthesis recipes, deposition techniques, materials properties and their influence on solar cell performance, including advanced characterization methods with materials selection and experimental techniques. By addressing the evolution of solar cell technologies, second generation thin-film photovoltaics, organic solar cells, and finally, the latest hybrid organic-inorganic approaches, this book benefits students and researchers in solar cell technology to understand the similarities, differences, benefits and challenges of each device. Introduces the basic concepts of different photovoltaic cells to audiences from a wide variety of academic backgrounds Consists of working principles of a particular category of solar technology followed by dissection of every component within the architecture Crucial experimental procedures for the fabrication of solar cell devices are introduced, aiding picture practical application of the technology

Perovskite solar cells (PSCs) have attracted significant attention in the scientific community due to a fast achievement in efficiencies reaching over 20 % within a few years of development. Despite this incredible enhancement, commercialization of PSCs is still a challenge owing to their rapid degradation. Thus, it is inevitable to understand the degradation mechanisms in PSCs to improve their stability. Methylammonium lead iodide (CH3NH3PbI3) is the most widely studied perovskite structure. This dissertation focuses on identifying the underlying causes related to the degradation of CH3NH3PbI3 based PSC devices and discusses possible ways to improve their stability. This thesis can be divided into four sections. Firstly, we analyzed interfacial interactions and chemical changes directly from complete PSC devices by employing laser desorption/ionization mass spectrometry (LDI-MS). A very prudent and systematic approach was undertaken for the very first time in case of PSCs to compare LDI-MS spectra from fresh and aged devices. We were able to trace molecular interactions and some prominent degradation products within PSC devices. Highlights of the observed transformations are corrosion of metal electrode, decomposition of the metal oxide layer, incorporation of oxygen atoms into perovskite, and formation of charge transfer complex between perovskite with the hole transport layer. LDI-MS method is a soft ionization technique. Thus, it has already become an inevitable analytical tool in life science research. Our results suggest that this method has the potential to make a revolution in the field of solar cell studies as well. Subsequently, we conducted a methodical study by using First-principles calculation within DFT formalism to understand how the choice of different metal oxide layers affect the charge transfer process as well as the stability of CH3NH3PbI3 (MAPI) perovskites. We compared the structure and electronic properties of MAPI based on TiO2, ZnO, and SnO2. Our calculation reveals the decomposition of methylammonium molecules by losing protons at MAPI/TiO2 and MAPI/ZnO interfaces. Bader charge analysis indicates the lowest charge transfer for interfaces of MAPI with ZnO. Although TiO2 based metal oxides contribute to more efficient charge transfer, still SnO2 was found to be a feasible choice in order to balance between efficiency and long-term stability of PSC devices. In the third part, we evaluated the effect of the electron transport layer (ETL) passivation on the stability of PSC devices. Devices were based on SnO2 electron transport layer. The behaviour of PSC devices was compared for three different ETL passivation layers using Indene C60 bisadduct (ICBA), Phenyl-C61-butyric acid methyl ester (PC61BM),Poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9–dioctylfluorene)] (PFN) respectively. Further investigations on devices with or without passivation layers revealed notable improvement in stability and efficiency of PSCs upon incorporating ETL passivation layer. Thin film characterizations indicated how might the passivation layer positively influence the performance of PSC devices. ICBA passivated SnO2 ETL showed the best PCE of 16.7%, retaining around 84% of the initial efficiency after being stored in ambient condition for ten days without any encapsulation. Finally, we studied the influence of CH3NH3PbI3 passivation on the device stability of PSCs. A systematic comparison was conducted among devices based on three different perovskite passivation layers named Poly(9-vinylcarbazole) (PVK), Polyvinylpyrrolidone (PVP) and Poly(3-hexylthiophene-2,5-diyl) (P3HT). Our results showed significant improvement in the stability of perovskite passivated PSCs compared with devices without passivation. Additional thin film characterizations explored the beneficial effect of passivation on perovskites. The highest efficiency of 14.88 % was obtained from unencapsulated PVK passivated devices demonstrating around 89.9 % of the original efficiency even after 16 days of exposure in ambient condition.

Provides detailed descriptions of organic, inorganic, and hybrid solar cells and the latest developments in the quest to produce low-cost, long-lasting solar cells What will it take to transform solar energy from an important alternative source to a truly competitive and, perhaps, dominant one? Lower cost and longer life. Organic, Inorganic, and Hybrid Solar Cells: Principles and Practice provides in-depth information on the three types of existing solar cells, giving readers a good foundation for evaluating the technologies with the most potential for competing with energy from fossil fuels. Featuring a Foreword written by Nobel Peace Prize co-winner Dr. Woodrow W. Clark, this timely and comprehensive guide: Focuses on the realization of low-cost and long-life solar cells study and applications Reviews the properties of inorganic materials, primarily semiconductors Explores the electrical and optical properties of organic materials Discusses the interfacing of organic and inorganic materials: compatibility of deposition, the adhesion problem, formation of surface states, and band-level realignment Provides a detailed description of organic-inorganic hybrid solar cells, from the basic principles to practical devices Introduces a sandwiched structure for hybrid solar cells, which combines a far lower production cost than inorganic solar cells while stabilizing and extending the life of organic material far beyond that of organic solar cells Organic, Inorganic, and Hybrid Solar Cells: Principles and Practice is a first-rate professional reference for electrical engineers and important supplemental reading for graduate students in related areas of study.

Developing a fundamental understanding of photocurrent generation processes at organic-inorganic interfaces is critical for improving hybrid solar cell efficiency and stability. This dissertation explores processes at these interfaces by combining data from photovoltaic device performance tests with characterization experiments conducted directly on the device. The dissertation initially focuses on exploring how morphologically and chemically modifying the organic-inorganic interface, between poly(3-hexylthiophene) (P3HT) as the electron donating light absorbing polymer and titanium dioxide (TiO2) as the electron acceptor, can result in stable and efficient hybrid solar cells. Given the heterogeneity which exists within bulk heterojunction devices, stable interfacial prototypes with well-defined interfaces between bilayers of TiO2 and P3HT were developed, which demonstrate tunable efficiencies ranging from 0.01 to 1.6 %. Stability of these devices was improved by using Cu-based hole collecting electrodes. Efficiency values were tailored by changing TiO2 morphology and by introducing sulfide layers like antimony trisulfide (Sb2S3) at the P3HT-TiO2 interface. The simple bilayer device design developed in this dissertation provides an opportunity to study the precise role played by nanostructured TiO2 surfaces and interfacial modifiers using a host of characterization techniques directly on a working device. Examples introduced in this dissertation include X-ray photoelectron spectroscopy (XPS) depth profiling analysis of metal-P3HT and P3HT-TiO2 interfaces and Raman analysis of bonding between interface modifiers like Sb2S3 and P3HT. The incompatibility of TiO2 with P3HT was significantly reduced by using P3HT derivatives with -COOH moieties at the extremity of a polymer chain. The role of functional groups like -COOH in interfacial charge separation phenomena was studied by comparing the photovoltaic behavior of these devices with those based on pristine P3HT. Finally, for hybrid solar cells discussed in this dissertation to become commercially viable, high temperature processing steps of the inorganic TiO2 layer must be avoided. Accordingly, this dissertation demonstrates the novel use of electromagnetic radiation in the form of microwaves to catalyze growth of anatase TiO2 thin films at temperatures as low as 150 °C, which is significantly lower than that used in conventional techniques. This low temperature process can be adapted to a variety of substrates and can produce patterned films. Accordingly, the ability to fabricate TiO2 thin films by the microwave process at low temperatures is anticipated to have a significant impact in processing devices based on plastics.

Printable Solar Cells The book brings together the recent advances, new and cutting edge materials from solution process and manufacturing techniques that are the key to making photovoltaic devices more efficient and inexpensive. Printable Solar Cells provides an overall view of the new and highly promising materials and thin film deposition techniques for printable solar cell applications. The book is organized in four parts. Organic and inorganic hybrid materials and solar cell manufacturing techniques are covered in Part I. Part II is devoted to organic materials and processing technologies like spray coating. This part also demonstrates the key features of the interface engineering for the printable organic solar cells. The main focus of Part III is the perovskite solar cells, which is a new and promising family of the photovoltaic applications. Finally, inorganic materials and solution based thin film formation methods using these materials for printable solar cell application is discussed in Part IV. Audience The book will be of interest to a multidisciplinary group of fields, in industry and academia, including physics, chemistry, materials science, biochemical engineering, optoelectronic information, photovoltaic and renewable energy engineering, electrical engineering, mechanical and manufacturing engineering.

This book delivers a comprehensive evaluation of organic and hybrid solar cells and identifies their fundamental principles and numerous applications. Great attention is given to the charge transport mechanism, donor and acceptor materials, interfacial materials, alternative electrodes, device engineering and physics, and device stability. The authors provide an industrial perspective on the future of photovoltaic technologies.

Organic photovoltaics (OPV) are a new generation of solar cells with the potential to offer very short energy pay back times, mechanical flexibility and significantly lower production costs compared to traditional crystalline photovoltaic systems. A weakness of OPV is their comparative instability during operation and this is a critical area of research towards the successful development and commercialization of these 3rd generation solar cells. Covering both small molecule and polymer solar cells, Stability and Degradation of Organic and Polymer Solar Cells summarizes the state of the art understanding of stability and provides a detailed analysis of the mechanisms by which degradation occurs. Following an introductory chapter which compares different photovoltaic technologies, the book focuses on OPV degradation, discussing the origin and characterization of the instability and describing measures for extending the duration of operation. Topics covered include: Chemical and physical probes for studying degradation Imaging techniques Photochemical stability of OPV materials Degradation mechanisms Testing methods Barrier technology and applications Stability and Degradation of Organic and Polymer Solar Cells is an essential reference source for researchers in academia and industry, engineers and manufacturers working on OPV design, development and implementation.

This book addresses the principles and materials for the development of next-generation solar cells for a sustainable global society Discusses the structures, working principles, and limitations of solar cells as well as the improvement methods of their power-conversion efficiency Introduces generations of cells as photovoltaic devices, including third-generation solar cells such as organic solar cells, quantum dots solar cells, and organic–inorganic hybrid solar cells Focuses on the emerging perovskite solar cells (PSCs) and deals with their cell configuration, transport materials, and fabrication processes in detail.