Low Band-Gap Materials for Solar Cells

Organic solar cells (OSCs) are discussed at length in terms of its performance leading to the generation of electricity. The key materials required for OSCs are the small organic molecules having donor and acceptor with suitable light absorption and electro-chemical properties of low energy band gap. Various structural scaffolds are highlighted with their structural design leading to film forming in an orderly manner and this morphology of film having a pivotal role in photo-induced charge separation, migration and collection at an electrode. Present day research informs that OSCs involving non fullerene based donors and acceptors are functioning with high photo conversion efficiency [PCE] of >17% and are promising candidates for practical applications.

Hollow Nanostructures for Application in Solar Cells

Hollow nanostructures are nanoscale materials with interior cavities, high volumetric load capacity ratio and high porosity. This new generation structure has gained huge momentum in the field of energy storage and photovoltaics due to such promising physical and chemical features. This chapter highlights contributions of various works where hollow nanostructures of metals and carbonaceous materials had been used in solar cell over the last few years. The harnessing of efficiency with structural modifications in the hollow structures over the years was shown in various works. The effect of structure engineering on the performance of solar cell has been explained in detail where voids in metallic hollow nanostructure enhance light scattering and high charge recombination. Simultaneously, carbonaceous hollow nanostructured materials are considered to be the latest photoelectrode materials and designated to be alternatives for metallic hollow nanostructures counterpart due to their high feedstock availability and fabrication charges.

New Generation Transparent Conducting Electrode Materials for Solar Cell Technologies

Transparent conducting electrodes (TCEs) play a vital role for the fabrication of solar cells and pivoted almost 50% of the total cost. Recently several materials have been identified as TCEs in solar cell applications. Still, indium tin oxide (ITO) based TCEs have dominated the market due to their outstanding optical transparency and electrical conductivity. However, inadequate availability of indium has increased the price of ITO based TCEs, which attracts the researchers to find alternative materials to make solar technology economical. In this regard, various kinds of conducting materials are available and synthesized worldwide with high electrical conductivity and optical transparency in order to find alternative to ITO based electrodes. Especially, new generation nanomaterials have opened a new window for the fabrication of cost effective TCEs. Carbon nanomaterials such as graphene, carbon nanotubes (CNTs), metal nanowires (MNWs) and metal mesh (MMs) based electrodes especially attracted the scientific community for fabrication of low cost photovoltaic devices. In addition to it, various conducting polymers such as poly (3, 4-ethylene dioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) based TCEs have also showed their candidacy as an alternative to ITO based TCEs. Thus, the present chapter gives an overview on materials available for the TCEs and their possible use in the field of solar cell technology

Absorber Materials for Solar Cells

Solar cell production has grown rapidly in the last few decades. Essentially a solar cell (SC), known as a photovoltaic (PV) cell, is nothing more than a p-n junction, composed of a p-type and n-type semiconductor. The electric field is generated at the junction when electrons and holes pass towards the positive and negative terminals respectively. Light consists of photons, and when the light of a sufficient wavelength falls on the cells, the energy from the photon is passed to the valence band electrons, allowing electrons to move to a higher energy state called the conductive band. The entire process is carried out in the absorber layer that lies under the anti-reflective coating of the SC. Since most energy in sunlight and artificial light is within the visible range of electromagnetic radiation (EMR), a SC absorber can absorb radiation effectively at these wavelengths. Because a SC can be made using a variety of materials, its output depends solely on the properties of the material used. This chapter discusses different absorbent materials that are used for solar cells.

Carbon Nanomaterials Beyond Graphene for Solar Cell and Electrochemical Sensing

Carbon-based nanomaterials have different structures with excellent physical and electronic properties. Graphene and carbon nanomaterials are widely used in sensing areas due to its high positive effect on the response of modified electrodes. Their presence increases sensitivities and gives the lower detection limits and enhances the analytical performance of biosensors for food safety and environmental monitoring. In addition, carbon nanomaterials play an important role for the good exploitation of solar energy by developing new structures of silicon-based photovoltaic cells. In this work we report the effect of the most recent graphene and carbon nonmaterial used for electrochemical detection of substances. This chapter also presents an overview of solar cell synthesis using graphene and carbon nanomaterials.

Graphene Materials for Third Generation Solar Cell Technologies

Photovoltaic technology is the most sustainable source of renewable energy because sunlight radiation is free and readily available. Therefore, the materials required accessing this energy source, cost and the efficiency of conversion from solar to electricity is the topic of interest in continued research. Graphene as a sp2-hybridized 2-dimensional carbon with unique crystal and electronic properties comprising high charge carrier mobility, optical transparency, inexpensive, excellent mechanical strength and flexibility with chemical stability and inertness among others is a suitable material for application in various units of the different architectures in third generation solar cells. It can be applied as a semiconductor layer, electrolyte and counter-electrode in dye-sensitized solar cells; electrode, perovskite, electron and hole transporting layers in perovskite solar cells; and electrode, hole transporting layer and electron acceptor and donor in organic solar cells; in addition to graphene/silicon Schottky junction. Following the application of graphene in various units of the third generation architecture, the power conversion efficiency has increased from 1.9% to over 22%, with ongoing research expected to develop a more stable design with longevity comparable to commercially available silicon-based p-n junction.

Monocrystalline Silicon Solar Cells

Monocrystalline silicon based solar cells have the attributes that includes elemental semiconductor nature and balancing properties making it extensively applicable in the field of microelectronics. Silicon based solar cells make about 90% of today’s photovoltaic technology. The highest experimental efficiency reported for monocrystalline solar cells so far is 26.6%. The V-I characteristics of monocrystalline silicon based solar cells have been deliberated in the contextual of silicon as substrate material. The theoretical value of Shockely-Queisser (SQ) limit for monocrystalline solar cells is 30% that invocate further efficiency developments. The typical monocrystalline structure and recent advancements in monocrystalline solar cells are emphasized with appropriate examples to understand the photovoltaic phenomenon. Power conversion efficiency (PCE) enhancement is of prime importance in photovoltaic industry (PV) and hence different techniques analyze the question of PCE in context of cost effective solar cell production. In light of the literature, the texturizing, anti-reflecting coating and metallization are proposed as the efficient methods for reduction in losses and enhancement in efficiency.

Material Challenges in Next Generation Solar Cells

Solar cells have emerged as a substitute for fuels, generating energy which is both renewable and pollution-free at reasonable prices. On the commercial scale, the silicon-based solar cells are still being used despite their efficiency decreasing over time. With the advancement in technology, efforts are being made to develop new materials for solar cells with higher efficiency and stability. The development of materials such as multijunctions, ultrathin films, quantum dots, dye sensitized materials, and perovskites has opened a new dimension to the solar cell technology. These are often referred to as next-generation materials for solar cell technology. In this chapter, an effort has been made to address the various issues these new generation solar technologies face and why there is a need to search for various new materials in order to improve and make these technologies commercially viable.