Solar Cells

Nanomaterials have emerged as a distinct class of modern materials. These materials are of significant importance due to their unique optical, electrical, thermal, and magnetic properties. Due to their tunable physical and chemical characteristics, including melting point, electrical conductivity, wettability, heat conductivity, light absorption, catalytic activity, and scattering, these materials have also gained recognition in high-tech engineering applications. These characteristics reflect better performance and working efficiency of nanomaterials relative to their bulk counterparts. Although there are many naturally occurring nanomaterials, most nanomaterials are engineered in laboratories. Such materials are purposefully synthesized in accordance with the industrial requirements. This chapter deals with the fundamentals of nanomaterials, their history, properties, and industrial applications. Different methods of synthesis of nanomaterials, their merits, demerits, and scale-up potential are also discussed in this chapter.

Solar cells have a great promise to solve the world energy crises in a sustainable way. In recent years, numerous efforts have been devoted on different aspects and performance of solar cells with a common task of achieving higher efficiency to compete with the traditional energy resources. Cost-effectiveness and enhancing power conversion efficiency are the major tasks in the photovoltaic technology. New field of nanotechnology has developed promising possibilities to improve the quality, stability, and performance of solar cells. Nanomaterials can contribute to solar cell design in different ways, which play an important role in their performances. Developments of nanomaterials-based solar cells could reduce the cost and stability for bulk power generation as well as enhance the power conversion efficiency. This book chapter reviews the performances of traditional solar cells and focuses on different contribution of advanced nanomaterials in solar cell advancement.

The present chapter gives an overview of third-generation solar cells with special emphasize on important synthesis protocol for ZnO, TiO₂, and rare earth-based upconverting materials for their utilization in the field of solar cells. Moreover, we have discussed working principle and basic requirements for organic-based solar cells, which is in major focus of research worldwide. This is booming research field and has enormous scope to serve humankind to combat energy scarcity and futuristic application for harvesting the solar energy.

The last years the growth of the global population has resulted in high demand for electricity consumption. Photovoltaic devices have shown a big potential to obtain energy power from solar irradiation when compared with other sources. Currently, photovoltaic silicon-based technologies are the most used around the world, but its high cost is still a big problem for global consumption. A short approach to fundamental concepts to inorganic and organic solar cells will be described in this chapter. Moreover, it will be showing new models of solar cells as well as advances and challenges in the development of inorganic and organic solar cells with high efficiency and stability.

Materials design for the next generation of solar cell technologies requires an efficient and cost-effective research approach to supplement experimental efforts. Computational research offers a theoretical guide by applying cutting edge methodologies to the study of electronic structures of newly predicted materials. In this chapter, we present our recent research efforts on sulfides. First, we will also provide a brief overview of oxide-based photovoltaic materials. We have conducted a density functional theory (DFT) study of two sulfide systems: acanthite Cu₂S and S-doped triclinic CuBiW₂O₈. With these two systems, we will demonstrate both the cation and anion doping mechanisms. In Cu₂S, we investigate the effects of various cation doping in Cu sites, namely Zn, Sn, Bi, Nb, and Ta and contrast their electronic structures with that of a previously studied Ag-doped Cu₂S system. A subsequent charge analysis provides a correlation between dopant charge states and detrimental mid-gap trap state concentrations. We then present our best dopant choice for Cu₂S-based photovoltaic systems. Finally, for CuBiW₂O₈, a new experimentally verified DFT-predicted quaternary oxide, the effects of S-anion-doping in O sites are studied, and results indicate favorable photovoltaic properties. This highlights the potential of S-anion-doping as a mechanism for engineering suitable band gaps for solar cell applications.

Improving the conversion efficiency and reducing cost are the major tasks to make more energy competitive-based photovoltaics and able to replace the traditional fossil energies. In organic/inorganic-based solar cell development, nanotechnology seems to be the most promising branch. Nanostructure materials with large band gap synthesized from III–V and II–VI elements are gaining more attention because of their potential use in emerging energy applications. Nanostructures with different morphologies including nanowires, nanosprings, nanobelts and nanocombs can be prepared. Variations in atomic arrangements to minimize the effect of electrostatic energies produces from different ionic charges on the polar surfaces are the major reason of diversified range of nanostructures. In this book chapter, we will focus on the contribution of different nanomaterials in the advancement of solar cell technology.

Unique structures and outstanding properties of carbon nanotubes (CNTs) have drawn significant attention of scientific community working in materials science and engineering. Researchers are taking interest in dealing with certain constraints of solar power systems and harnessing maximum energy from the sun. Construction, working life, manufacturing cost and efficiency of the solar cells are the key factors in defining their widespread use. Different strategies are being adopted to develop stable materials for manufacturing the low cost but highly efficient solar cells. Owing to high thermal stability, mechanical strength, surface area to volume ratio and electrical conductivity, CNTs can be a good choice as a solar cell material. CNT-based solar cells are fascinating the world due to their reduced manufacturing cost and high efficiency. Also, the future CNT-based hybrid solar cells would be much cheaper than the traditional energy source cells. This chapter discusses the carbon-based nanoscience and nanotechnology, structures and properties of CNTs, methods of synthesis of CNTs and use of CNTs in manufacturing the efficient solar cells.

The day–by-day increasing need for light energy has reduced the necessary supply of energy for mankind usage and hiked the prices of natural energy resources. To avoid energy tragedy in future, one needs to use the non-degrading sources of energy for energy harvesting. The advancement in solar cell technology allows us to convert the sunlight more efficiently into electrical energy, though the low cost with highly stable and efficient solar cells is still desirable. The dye-sensitized solar cells (DSSCs), a class of third-generation photovoltaic cell, have emerged out as economic, eco-friendly, and much easier fabrication process over other existing technologies such as single-crystal Si solar cells, polycrystalline Si solar cells, thin-film solar cells, and other semiconductor (GaAs, CdTe, CuInSe_2, etc.) thin films. The main challenge and limiting factor with DSSC’s fabrication are their efficiency and durability in the environment. In the last decade, enormous efforts have been made to improve the efficiency and stability of DSSCs. One of the possible ways is the manipulation of light at nanoscale on some metal–dielectric interface and integrating it on some cheaper electronic devices for highly efficient solar cell applications. On the other hand, the research on modifying the design and fabrication of photoanode, dyes materials, and counter electrode materials have paid huge attention in architecting DSSCs. This chapter provides an insight into the fabrication of DSSCs and the challenges associated with its fabrication, stability, and efficiency.

Energy crisis has become one of the main hurdles in the path of development and technology due to the rapid reduction of fossil. Renewable energy resources have gained the great importance in last few decades. Solar technology is considered as a potential candidate for energy in future. Solar technology has evolved in different generations from single crystal semiconductor wafer to quantum dot solar cells. Quantum dots act as absorbing photovoltaic material instead of bulk materials like silicon or copper indium gallium selenide in quantum dot solar cell (QDSC). Quantum dots have tunable band gaps that depend on their size that makes them a promising candidate for multi-junction solar cells. The photovoltaic conversion efficiency of quantum dot solar cells is much higher as compared to traditional solar cells. Various types of quantum dots like CdSe, CdS, PbS, GaAs, CdTe, ZnSe and graphene are used in different designs of quantum dot solar cells. In this chapter, we discussed the quantum dot solar cells (QDSCs), their design along with their various architectures and materials selection approaches in detail.

Perovskite Solar Cells (PSCs) based on organometal trihalide materials have gained enormous attention for photovoltaic applications due to its outstanding optical and electronic properties such as high absorption coefficient long carrier diffusion lengths, long carrier mobility and unique defect physics. As a result, the power conversion efficiency (PCE) of PSCs rapidly enhanced from 3.8 to 24% through the advancement made in processing methods, compositional tuning, and interface engineering. The dominant PSCs architecture has been evolved; n–i–p and p–i–n with mesoporous and planar heterojunction. In both configurations, i.e. planar or mesoporous, the perovskite material is sandwiched between electron and hole transporting layers and top electrode. The basic function of charge transporting layers is to improve charge collection efficiency and reduce charge recombination at interfaces. In the following chapter, we present the critical survey of the recent progress in perovskite absorber and charge transporting materials for the exceptionally higher PCE of perovskite devices. Furthermore, numerous fabrication techniques and device architectures are summarized.

Metal oxide-based electron transport layer (ETL) is one of the vital components in conventional n-i-p type perovskite solar cells (PSC) that enables efficient electron extraction and transport within the device. Nonetheless, native point defect associated with oxygen vacancies that naturally exist in the ETL materials such as TiO₂, SnO₂ and Nb₂O₅ could deteriorate the overall performance of the PSC. In this chapter, the intentional and unintentional formation of oxygen vacancies during the fabrication process of the ETL will be firstly clarified. The properties of oxygen vacancies in the viewpoint of structural, optical and electrical as well as surface wettability will also be profoundly elaborated to provide valuable insight on the impact of oxygen vacancies in the ETL towards efficiency, hysteresis and stability of PSC devices.

Optoelectronic devices including solar cells have been widely used in space and are extremely sensitive to substantially shorter wavelength electromagnetic radiations, e.g., gamma ray. Electrons and secondary photons are produced when gamma rays pass through the matter and this phenomenon can be described as Compton effect. When a photon interacts with a device, it removes the primary electron from an atom. That primary electron in each ionizing collision produces swift secondary electron which may have nearly as much kinetic energy as the primary photon. This secondary electron dissipates its energy as kinetic energy which results in the ionization and excitation of the atoms in the absorber. This kinetic energy eventually is dissipated in the medium as heat and imparted to the atom in order to displace it from its normal site producing vacancy-interstitial pair. Ultimately, lattice periodicity changes and give rise to additional energy levels and alter the electrical properties of optoelectronic devices.

Solar cell efficiency can be associated with the ability of the solar cell to produce the maximum amount of electricity from a light energy source. There are many uses of multi-junction solar cells based upon likewise in satellites and space vehicles. Physically based two-dimensional methods under ultra-high concentration above 1000 suns, the important limiting factors of multi-junction solar cells can be investigated. The single-junction solar cells that are merged with silicon and GaAs solar cells lead to the great importance due to 30% limit of intrinsic efficiency. In the present chapter, we have discussed the basic physics and operation of solar cells with multiple-junction cell designs of different types of materials, with a particular focus on the GaInP/GaAs/Ge tandem cells. Further, their performance based on different parameters will be discussed along with future consideration for developing most advances in high efficiency III–V multi-junction solar cells.