Query: Photovoltaic materials: Present efficiencies and future challenges

Candidate papers:

abstract: Surveying the solar cell landscape The rate of development and deployment of large scale photovoltaic systems over recent years has been unprecedented. Because the cost of photovoltaic systems is only partly determined by the cost of the solar cells, efficiency is a key driver to reduce the cost of solar energy. There are several materials systems being explored to achieve high efficiency at low cost. Polman et al. comprehensively and systematically review the leading candidate materials, present the limitations of each system, and analyze how these limitations can be overcome and overall cell performance improved. Science, this issue p. 10.1126/science.aad4424 BACKGROUND Photovoltaics, which directly convert solar energy into electricity, offer a practical and sustainable solution to the challenge of meeting the increasing global energy demand. According to the Shockley Queisser (S Q) detailed balance model, the limiting photovoltaic energy conversion efficiency for a single junction solar cell is 33.7% for an optimum semiconductor band gap of 1.34 eV. Parallel to the development of wafer based Si solar cells, for which the record efficiency has continually increased during recent decades, a large range of thin film materials have been developed with the aim to approach the S Q limit. These materials can potentially be deposited at low cost, in flexible geometries, and using relatively small material quantities. ADVANCES We review the electrical characteristics of record efficiency cells made from 16 widely studied photovoltaic material geometries and illuminated under the standard AM1.5 solar spectrum, and compare these to the fundamental limits based on the S Q model. Cells that show a short circuit current (Jsc) lower than the S Q limit suffer from incomplete light absorption or incomplete collection of generated carriers, whereas a reduced open circuit voltage (Voc) or fill factor (FF) reflects unwanted bulk or interfacial carrier recombination, parasitic resistance, or other electrical nonidealities. The figure shows the experimental values for Jsc and the Voc x FF product relative to the S Q limiting values for the different materials. This graph enables a direct identification of each material in terms of unoptimized light management and carrier collection (Jsc/JSQ 1) or carrier management (Voc x FF/VSQ x FFSQ 1) Monocrystalline Si cells (record efficiency 25.6% have reached near complete light trapping and carrier collection and are mostly limited by remaining carrier recombination losses. In contrast, thin film single crystalline GaAs cells (28.8% show only minimal recombination losses but can be improved by better light management. Polycrystalline CdTe thin film cells (21.5% offer excellent light absorption but have relatively high recombination losses; perovskite cells (21.0% and Cu(In,Ga)(Se,S)2 (CIGS) cells (21.7% have poorer light management, although CIGS displays higher electrical quality. Aside from these five materials (Si, GaAs, CdTe, CIGS, perovskite) with efficiencies of >20% a broad range of other thin film materials have been developed with efficiencies of 10 to 12% micro/nanocrystalline and amorphous Si, Cu(Zn,Sn)(Se,S)2 (CZTS) dye sensitized TiO2, organic polymer materials, and quantum dot solids. So far, cell designs based on these materials all suffer from both light management and carrier management problems. Organic and quantum dot solar cells have shown substantial efficiency improvements in recent years. OUTLOOK The record efficiency single crystalline materials (Si, GaAs) have room for efficiency improvements by a few absolute percent. The future will tell whether the high efficiency polycrystalline thin films (CdTe, CIGS, perovskite) can rival the efficiencies of Si and GaAs. Because the cost of photovoltaic systems is only partly determined by the cost of the solar cells, efficiency is a key driver to reduce the cost of solar energy, and therefore large area photovoltaic systems require high efficiency >20% low cost solar cells. The lower efficiency (flexible) materials can find applications in building integrated PV systems, flexible electronics, flexible power generation systems, and many other (sometimes niche) markets. High efficiency >20% materials find applications in large area photovoltaic power generation for the utility grid as well as in small and medium sized systems for the built environment. They will enable very large scale penetration into our energy system, starting now and growing as the cost per kilowatt hour is reduced further by a factor of 2 to 3. This can be achieved by nanophotonic cell designs, in which optically resonant and nonresonant structures are integrated with the solar cell architecture to enhance light coupling and trapping, in combination with continued materials engineering to further optimize cell voltage. Making big steps forward in these areas will require a coordinated international materials science and engineering effort. Limiting processes in photovoltaic materials. An efficient solar cell captures and traps all incident light "light management" and converts it to electrical carriers that are efficiently collected "carrier management" The plot shows the short circuit current and product of open circuit voltage and fill factor relative to the maximum achievable values, based on the Shockley Queisser detailed balance limit, for the most efficient solar cell made with each photovoltaic material. The data indicate whether a particular material requires better light management, carrier management, or both. Colors correspond to cells achieving <50% of their S Q efficiency limit eSQ (red) 50 to 75% (green) or >75% (blue) Recent developments in photovoltaic materials have led to continual improvements in their efficiency. We review the electrical characteristics of 16 widely studied geometries of photovoltaic materials with efficiencies of 10 to 29% Comparison of these characteristics to the fundamental limits based on the Shockley Queisser detailed balance model provides a basis for identifying the key limiting factors, related to efficient light management and charge carrier collection, for these materials. Prospects for practical application and large area fabrication are discussed for each material.
author_names: Albert Polman

Mark W Knight

Erik C Garnett

Bruno Ehrler

Wim C Sinke
title: Photovoltaic materials: Present efficiencies and future challenges
venue: Science
year: 2016

abstract: This chapter is dedicated to present the state of the art of hybrid photovoltaic thermoelectric generators based on either organic or inorganic photovoltaic cells. Present challenges and future perspectives of this approach to energy harvesting will be discussed with a special emphasis on materials issues. It will be seen that both classes of PV materials deserve attention in view of applications in hybridized converters, although absorber stability and degradation of its PV efficiency with increasing temperatures sets limitations to currently achievable efficiencies, also in view of the still low efficiency of thermoelectric stages.
author_names: Dario Narducci

Peter Bermel

Bruno Lorenzi

Ning Wang

Kazuaki Yazawa
title: Hybrid Photovoltaic Thermoelectric Generators: Materials Issues
year: 2018

abstract: Metal halide based perovskite solar cells (PSCs) are considered among the most promising photovoltaic technologies, and already present certified efficiencies that surpass 22 The high performance and low fabrication cost make this technology competitive with that of state of the art thin film photovoltaics. However, PSCs present some striking disadvantages that hinder their commercialization, including short operational lifetimes, high toxicity, and hysteresis effects, which lower both the performance and long term stability of the devices. Herein, work conducted within the last two years is summarized with regard to addressing the challenges of low temperature processed planar inverted PSCs composed of graphene based materials. In addition, critical challenges and the prospects of this field are discussed and some prospects for future research directions are proposed.
author_names: Konstantinos Petridis

George Kakavelakis

Minas M Stylianakis

Emmanuel Kymakis
title: Graphene Based Inverted Planar Perovskite Solar Cells: Advancements, Fundamental Challenges, and Prospects.
venue: Chemistry, an Asian journal
year: 2018

abstract: Organic Solar Cells (OSCs) represent a recent photovoltaic (PV) technology that uses organic semiconductor materials to convert sunlight into electric energy. OSCs have recently shown significant attention due to their technological advantages of flexibility, light weight, cost effective fabrication and significant improvement in the power conversion efficiency. But the efficiencies of OSCs are still lower than crystal or inorganic silicon solar cells. By studying the photovoltaic properties of organic solar cells it is possible to increase the cells efficiency. If the efficiency can be raises to half of the inorganic solar cell the production cost will be reduced to one tenth. This paper describes the historical back ground, present situation, future prospectus and technological breakthrough of OSCs. Also explain the long term sustainability advantages of OSCs with compared to inorganic photovoltaic technologies in terms of energy payback time and CO2 emission.
author_names: M M Rhaman

Mohammad A Matin
title: Organic Solar Cells: Historical developments and challenges
venue: 2015 International Conference on Advances in Electrical Engineering (ICAEE)
year: 2015

abstract: Summary Despite the relevance of thermophotovoltaic (TPV) conversion to many emerging energy technologies, identifying which aspects of current TPV designs are favorable and where opportunities for improvement remain is challenging because of the experimental variability in TPV literature, including emitter and cell temperatures, cavity geometry, and system scale. This review examines several decades of experimental TPV literature and makes meaningful comparisons across TPV reports by comparing each energy conversion step to its respective, experiment specific thermodynamic limit. We find that peak reported efficiencies are nearing 50% of their thermodynamic limit. Emitter cell pairs that best manage the broad spectrum of thermal radiation exhibit the best efficiencies. Large gains in peak efficiency are expected from further suppression of sub bandgap radiative transfer, as well as improvements in carrier management that address bandgap underutilization and Ohmic losses. Furthermore, there is a noticeable practical gap between the leading material pairs and integrated devices, mainly due to a lack of scaled up high performance materials, which exposes surfaces to parasitic heat loss. Provided these challenges are overcome, TPVs may ultimately provide power on demand and near the point of use, enabling greater integration of intermittent renewables.
author_names: Tobias Burger

Caroline Sempere

Bosun Roy-Layinde

Andrej Lenert
title: Present Efficiencies and Future Opportunities in Thermophotovoltaics
year: 2020

abstract: Metal halide perovskite solar cells are emerging candidates for next generation thin film photovoltaic devices with the potential for extremely low fabrication cost and high power conversion efficiency. Perovskite solar cells have demonstrated a rapid development in device performance over the last decade, from an initial 3.81% to a most recently certified 24.2% though the challenges of long term stability and lead toxicity still remain. Carbon materials, ranging from zero dimensional carbon quantum dots to three dimensional carbon black materials, are promising candidates for the enhancement of both efficiency and stability of perovskite solar cells, offering unique advantages for incorporation into various device architectures. In this review article, we present a concise overview of important and exciting advancements of perovskite solar cells that incorporate different dimensions of carbon material in their device architectures in an effort to simultaneously improve device performance and long term stability. We also discuss the major advantages and potential challenges of each technique that has been developed in the most recent work. Finally, we outline the future opportunities toward more efficient and stable perovskite solar cells utilizing carbon materials.
author_names: Victoria Ferguson

S Ravi P Silva

Wuzhi Zhang
title: Carbon Materials in Perovskite Solar Cells: Prospects and Future Challenges
venue: ENERGY ENVIRONMENTAL MATERIALS
year: 2019

abstract: Photovoltaic (PV) systems are regarded as clean and sustainable sources of energy. Although the operation of PV systems exhibits minimal pollution during their lifetime, the probable environmental impacts of such systems from manufacturing until disposal cannot be ignored. The production of hazardous contaminates, water resources pollution, and emissions of air pollutants during the manufacturing process as well as the impact of PV installations on land use are important environmental factors to consider. The present study aims at developing a comprehensive analysis of all possible environmental challenges as well as presenting novel design proposals to mitigate and solve the aforementioned environmental problems. The emissions of greenhouse gas (GHG) from various PV systems were also explored and compared with fossil fuel energy resources. The results revealed that the negative environmental impacts of PV systems could be substantially mitigated using optimized design, development of novel materials, minimize the use of hazardous materials, recycling whenever possible, and careful site selection. Such mitigation actions will reduce the emissions of GHG to the environment, decrease the accumulation of solid wastes, and preserve valuable water resources. The carbon footprint emission from PV systems was found to be in the range of 14 73 g CO2 eq/kWh, which is 10 to 53 orders of magnitude lower than emission reported from the burning of oil (742 g CO2 eq/kWh from oil) It was concluded that the carbon footprint of the PV system could be decreased further by one order of magnitude using novel manufacturing materials. Recycling solar cell materials can also contribute up to a 42% reduction in GHG emissions. The present study offers a valuable management strategy that can be used to improve the sustainability of PV manufacturing processes, improve its economic value, and mitigate its negative impacts on the environment.
author_names: Muhammad Tawalbeh

Amani Al-Othman

Feras Kafiah

Emad Abdelsalam

Fares Almomani

Malek Alkasrawi
title: Environmental impacts of solar photovoltaic systems: A critical review of recent progress and future outlook.
venue: The Science of the total environment
year: 2020

abstract: Porous organic polymers are materials with covalently bonded (hydro)thermally stable backbones exhibiting high and accessible surface areas, and properties which are intriguing in the field of (opto)electronics. Especially in organic photovoltaics (OPVs) the electron rich backbone of this class of materials provides exceptional light absorption properties for improved charge formation/separation. Particularly for devices operating via bulk heterojunctions, the rigid open voids along the porous skeleton are rather interesting for improved phase separation and act as an ideal host to the prospective acceptors. Furthermore, their high dimensional geometry allows them to transport electrons/holes independent of orientation issues. However, the non soluble nature of this class of materials limits their processability for forming uniform films, which is essential for device fabrication. In this review, a brief overview on the reported OPV devices fabricated by applying porous organic polymers in the active layer with the corresponding methods used for film formation will be presented, which will be followed by a discussion regarding possible improvements on the film formation methods and suggestions upon enhancement of the structural/electronic feasibility of the porous backbone.
author_names: Hakan Bildirir

Vasilis G Gregoriou

Apostolos Avgeropoulos

Ullrich Scherf

Christos L Chochos
title: Porous organic polymers as emerging new materials for organic photovoltaic applications: current status and future challenges
year: 2017

abstract: In order to achieve photovoltaic technologies' commercial availability, high power conversion efficiency, low cost, large area, low toxicity, and long lifetime are crucial attributes. In recent years, perovskite materials have emerged as one of the most studied photovoltaic materials for its high performance and cost effectiveness. However, the development of protocols to industrialize the perovskite technology still faces several severe challenges. In this chapter, we summarize the challenges and obstacles of perovskite material research from four aspects. For successful commercialization, the high stability and long term lifetime is primary and essential. Second, Lead toxicity is also an important obstacle for practical application due to its threat to human health Third, for improving the fabrication repeatability, hysteresis and relevant measurement standards is discussed. Finally, the capacity to fabricate large area and flexible modules based on recently reported state of the art perovskite solar cells are also discussed.
author_names: Lin Fu

Bo Li

Shuang Li

Longwei Yin
title: Future Challenges of the Perovskite Materials
year: 2020

abstract: Over the last decade, the research trends on PV systems are mainly focused on improving reliability, efficiency, and power quality, reducing the cost, integrating at various scales with a grid and contributing to development of microgrid and smart grid solutions. At the same time, many companies in recent years have been focusing on building integrated PV systems, solar flowers, solar roadways, solar street lights and other innovative solutions for the built environment. This paper presents a review of the past and present status, as well as the future challenges of solar photovoltaic technology in the built environment. The main focus in the paper is put on a current technology, contemporary research trends and future challenges. The various aspects related to the global renewable energy sources and the PV markets, the cost and technology of photovoltaic modules are addressed and discussed. DOI: http:/dx.doi.org/10.5755/j01.sace.23.2.21268
author_names: Rokas Valancius

Anies Mutiari

Anju Singh

Cynthia Alexander

Diana Arteta De La Cruz

Federico E del Pozo
title: Solar Photovoltaic Systems in the Built Environment: Today Trends and Future Challenges
year: 2018