Showing papers on "Solar cell published in 2011"

Handbook of photovoltaic science and engineering

Abstract: About the Editors. List of Contributors. Preface to the 2nd Edition. 1 Achievements and Challenges of Solar Electricity from Photovoltaics (Steven Hegedus and Antonio Luque). 1.1 The Big Picture. 1.2 What is Photovoltaics? 1.3 Photovoltaics Today. 1.4 The Great Challenge. 1.5 Trends in Technology. 1.6 Conclusions. 2 The Role of Policy in PV Industry Growth: Past, Present and Future (John Byrne and Lado Kurdgelashvili). 2.1 Introduction. 2.2 Policy Review of Selected Countries. 2.3 Policy Impact on PV Market Development. 2.4 Future PV Market Growth Scenarios. 2.5 Toward a Sustainable Future. 3 The Physics of the Solar Cell (Jeffery L. Gray). 3.1 Introduction. 3.2 Fundamental Properties of Semiconductors. 3.3 Solar Cell Fundamentals. 3.4 Additional Topics. 3.5 Summary. 4 Theoretical Limits of Photovoltaic Conversion and New-generation Solar Cells (Antonio Luque and Antonio Marti). 4.1 Introduction. 4.2 Thermodynamic Background. 4.3 Photovoltaic Converters. 4.4 The Technical Efficiency Limit for Solar Converters. 4.5 Very-high-efficiency Concepts. 4.6 Conclusions. 5 Solar Grade Silicon Feedstock (Bruno Ceccaroli and Otto Lohne). 5.1 Introduction. 5.2 Silicon. 5.3 Production of Silicon Metal/Metallurgical Grade Silicon. 5.4 Production of Polysilicon/Silicon of Electronic and Photovoltaic Grade. 5.5 Current Silicon Feedstock to Solar Cells. 5.6 Requirements of Silicon for Crystalline Solar Cells. 5.7 Routes to Solar Grade Silicon. 5.8 Conclusions. 6 Bulk Crystal Growth and Wafering for PV (Hugo Rodriguez, Ismael Guerrero, Wolfgang Koch, Arthur L. Endros, Dieter Franke, Christian Hassler, Juris P. Kalejs and H. J. Moller). 6.1 Introduction. 6.2 Bulk Monocrystalline Material. 6.3 Bulk Multicrystalline Silicon. 6.4 Wafering. 6.5 Silicon Ribbon and Foil Production. 6.6 Numerical Simulations of Crystal Growth Techniques. 6.7 Conclusions. 7 Crystalline Silicon Solar Cells and Modules (Ignacio Tobias, Carlos del Ca"nizo and Jesus Alonso). 7.1 Introduction. 7.2 Crystalline Silicon as a Photovoltaic Material. 7.3 Crystalline Silicon Solar Cells. 7.4 Manufacturing Process. 7.5 Variations to the Basic Process. 7.6 Other Industrial Approaches. 7.7 Crystalline Silicon Photovoltaic Modules. 7.8 Electrical and Optical Performance of Modules. 7.9 Field Performance of Modules. 7.10 Conclusions. 8 High-efficiency III-V Multijunction Solar Cells (D. J. Friedman, J. M. Olson and Sarah Kurtz). 8.1 Introduction. 8.2 Applications. 8.3 Physics of III-V Multijunction and Single-junction Solar Cells. 8.4 Cell Configuration. 8.5 Computation of Series-connected Device Performance. 8.6 Materials Issues Related to GaInP/GaAs/Ge Solar Cells. 8.7 Epilayer Characterization and Other Diagnostic Techniques. 8.8 Reliability and Degradation. 8.9 Future-generation Solar Cells. 8.10 Summary. 9 Space Solar Cells and Arrays (Sheila Bailey and Ryne Raffaelle). 9.1 The History of Space Solar Cells. 9.2 The Challenge for Space Solar Cells. 9.3 Silicon Solar Cells. 9.4 III-V Solar Cells. 9.5 Space Solar Arrays. 9.6 Future Cell and Array Possibilities. 9.7 Power System Figures of Merit. 9.8 Summary. 10 Photovoltaic Concentrators (Gabriel Sala and Ignacio Anton). 10.1 What is the Aim of Photovoltaic Concentration and What Does it Do? 10.2 Objectives, Limitations and Opportunities. 10.3 Typical Concentrators: an Attempt at Classification. 10.4 Concentration Optics: Thermodynamic Limits. 10.5 Factors of Merit for Concentrators in Relation to the Optics. 10.6 Photovoltaic Concentration Modules and Assemblies. 10.7 Tracking for Concentrator Systems. 10.8 Measurements of Cells, Modules and Photovoltaic Systems in Concentration. 10.9 Summary. 11 Crystalline Silicon Thin-Film Solar Cells via High-temperature and Intermediate-temperature Approaches (Armin G. Aberle and Per I. Widenborg). 11.1 Introduction. 11.2 Modelling. 11.4 Crystalline Silicon Thin-Film Solar Cells on Intermediate-T Foreign Supporting Materials. 11.5 Conclusions. 12 Amorphous Silicon-based Solar Cells (Eric A. Schiff, Steven Hegedus and Xunming Deng). 12.1 Overview. 12.2 Atomic and Electronic Structure of Hydrogenated Amorphous Silicon. 12.3 Depositing Amorphous Silicon. 12.4 Understanding a-Si pin Cells. 12.5 Multijunction Solar Cells. 12.6 Module Manufacturing. 12.7 Conclusions and Future Projections. 13 Cu(InGa)Se2 Solar Cells (William N. Shafarman, Susanne Siebentritt and Lars Stolt). 13.1 Introduction. 13.2 Material Properties. 13.3 Deposition Methods. 13.4 Junction and Device Formation. 13.5 Device Operation. 13.6 Manufacturing Issues. 13.7 The Cu(InGa)Se2 Outlook. 14 Cadmium Telluride Solar Cells (Brian E. McCandless and James R. Sites). 14.1 Introduction. 14.2 Historical Development. 14.3 CdTe Properties. 14.4 CdTe Film Deposition. 14.5 CdTe Thin Film Solar Cells. 14.6 CdTe Modules. 14.7 Future of CdTe-based Solar Cells. 15 Dye-sensitized Solar Cells (Kohjiro Hara and Shogo Mori). 15.1 Introduction. 15.2 Operating Mechanism of DSSC. 15.3 Materials. 15.4 Performance of Highly Efficient DSSCs. 15.5 Electron-transfer Processes. 15.6 New Materials. 15.7 Stability. 15.8 Approach to Commercialization. 15.9 Summary and Prospects. 16 Sunlight Energy Conversion Via Organics (Sam-Shajing Sun and Hugh O'Neill). 16.1 Principles of Organic and Polymeric Photovoltaics. 16.2 Evolution and Types of Organic and Polymeric Solar Cells. 16.3 Organic and Polymeric Solar Cell Fabrication and Characterization. 16.4 Natural Photosynthetic Sunlight Energy Conversion Systems. 16.5 Artificial Photosynthetic Systems. 16.6 Artificial Reaction Centers. 16.7 Towards Device Architectures. 16.8 Summary and Future Perspectives. 17 Transparent Conducting Oxides for Photovoltaics (Alan E. Delahoy and Sheyu Guo). 17.1 Introduction. 17.2 Survey of Materials. 17.3 Deposition Methods. 17.4 TCO Theory and Modeling: Electrical and Optical Properties and their Impact on Module Performance. 17.5 Principal Materials and Issues for Thin Film and Wafer-based PV. 17.6 Textured Films. 17.7 Measurements and Characterization Methods. 17.8 TCO Stability. 17.9 Recent Developments and Prospects. 18 Measurement and Characterization of Solar Cells and Modules (Keith Emery). 18.1 Introduction. 18.2 Rating PV Performance. 18.3 Current-Voltage Measurements. 18.4 Spectral Responsivity Measurements. 18.5 Module Qualification and Certification. 18.6 Summary. 19 PV Systems (Charles M. Whitaker, Timothy U. Townsend, Anat Razon, Raymond M. Hudson and Xavier Vallve). 19.1 Introduction: There is gold at the end of the rainbow. 19.2 System Types. 19.3 Exemplary PV Systems. 19.4 Ratings. 19.5 Key System Components. 19.6 System Design Considerations. 19.7 System Design. 19.8 Installation. 19.9 Operation and Maintenance/Monitoring. 19.10 Removal, Recycling and Remediation. 19.11 Examples. 20 Electrochemical Storage for Photovoltaics (Dirk Uwe Sauer). 20.1 Introduction. 20.2 General Concept of Electrochemical Batteries. 20.3 Typical Operation Conditions of Batteries in PV Applications. 20.4 Secondary Electrochemical Accumulators with Internal Storage. 20.5 Secondary Electrochemical Battery Systems with External Storage. 20.6 Investment and Lifetime Cost Considerations. 20.7 Conclusion. 21 Power Conditioning for Photovoltaic Power Systems (Heribert Schmidt, Bruno Burger and Jurgen Schmid). 21.1 Charge Controllers and Monitoring Systems for Batteries in PV Power Systems. 21.2 Inverters. 22 Energy Collected and Delivered by PV Modules (Eduardo Lorenzo). 22.1 Introduction. 22.2 Movement between Sun and Earth. 22.3 Solar Radiation Components. 22.4 Solar Radiation Data and Uncertainty. 22.5 Radiation on Inclined Surfaces. 22.6 Diurnal Variations of the Ambient Temperature. 22.7 Effects of the Angle of Incidence and of Dirt. 22.8 Some Calculation Tools. 22.9 Irradiation on Most Widely Studied Surfaces. 22.10 PV Generator Behaviour Under Real Operation Conditions. 22.11 Reliability and Sizing of Stand-alone PV Systems. 22.12 The Case of Solar Home Systems. 22.13 Energy Yield of Grid-connected PV Systems. 22.14 Conclusions. 23 PV in Architecture (Tjerk H. Reijenga and Henk F. Kaan). 23.1 Introduction. 23.2 PV in Architecture. 23.3 BIPV Basics. 23.4 Steps in the Design Process with PV. 23.5 Concluding Remarks. 24 Photovoltaics and Development (Jorge M. Huacuz, Jaime Agredano and Lalith Gunaratne). 24.1 Electricity and Development. 24.2 Breaking the Chains of Underdevelopment. 24.3 The PV Alternative. 24.4 Examples of PV Rural Electrification. 24.5 Toward a New Paradigm for Rural Electrification. References. Index.

6.5% efficient perovskite quantum-dot-sensitized solar cell

Abstract: Highly efficient quantum-dot-sensitized solar cell is fabricated using ca. 2–3 nm sized perovskite (CH3NH3)PbI3 nanocrystal. Spin-coating of the equimolar mixture of CH3NH3I and PbI2 in γ-butyrolactone solution (perovskite precursor solution) leads to (CH3NH3)PbI3 quantum dots (QDs) on nanocrystalline TiO2 surface. By electrochemical junction with iodide/iodine based redox electrolyte, perovskite QD-sensitized 3.6 μm-thick TiO2 film shows maximum external quantum efficiency (EQE) of 78.6% at 530 nm and solar-to-electrical conversion efficiency of 6.54% at AM 1.5G 1 sun intensity (100 mW cm−2), which is by far the highest efficiency among the reported inorganic quantum dot sensitizers.

Electrochemical Considerations for Determining Absolute Frontier Orbital Energy Levels of Conjugated Polymers for Solar Cell Applications

Abstract: Narrow bandgap conjugated polymers in combination with fullerene acceptors are under intense investigation in the field of organic photovoltaics (OPVs). The open circuit voltage, and thereby the power conversion efficiency, of the devices is related to the offset of the frontier orbital energy levels of the donor and acceptor components, which are widely determined by cyclic voltammetry. Inconsistencies have appeared in the use of the ferrocenium/ferrocene (Fc + /Fc) redox couple, as well as the values used for the absolute potentials of standard electrodes, which can complicate the comparison of materials properties and determination of structure/property relationships.

Peak external photocurrent quantum efficiency exceeding 100% via MEG in a quantum dot solar cell.

Abstract: Multiple exciton generation (MEG) is a process that can occur in semiconductor nanocrystals, or quantum dots (QDs), whereby absorption of a photon bearing at least twice the bandgap energy produces two or more electron-hole pairs. Here, we report on photocurrent enhancement arising from MEG in lead selenide (PbSe) QD-based solar cells, as manifested by an external quantum efficiency (the spectrally resolved ratio of collected charge carriers to incident photons) that peaked at 114 ± 1% in the best device measured. The associated internal quantum efficiency (corrected for reflection and absorption losses) was 130%. We compare our results with transient absorption measurements of MEG in isolated PbSe QDs and find reasonable agreement. Our findings demonstrate that MEG charge carriers can be collected in suitably designed QD solar cells, providing ample incentive to better understand MEG within isolated and coupled QDs as a research path to enhancing the efficiency of solar light harvesting technologies.

Molecular design and ordering effects in π-functional materials for transistor and solar cell applications.

Abstract: Organic electronics are broadly anticipated to impact the development of flexible thin-film device technologies. Among these, solution-processable π-conjugated polymers and small molecules are proving particularly promising in field-effect transistors and bulk heterojunction solar cells. This Perspective analyzes some of the most exciting strategies recently suggested in the design and structural organization of π-functional materials for transistor and solar cell applications. Emphasis is placed on the interplay between molecular structure, self-assembling properties, nanoscale and mesoscale ordering, and device efficiency parameters. A critical look at the various approaches used to optimize both materials and device performance is provided to assist in the identification of new directions and further advances.

Nanowire Solar Cells

Abstract: The nanowire geometry provides potential advantages over planar waferbased or thin-film solar cells in every step of the photoconversion process. These advantages include reduced reflection, extreme light trapping, improved band gap tuning, facile strain relaxation, and increased defect tolerance. These benefits are not expected to increase the maximum efficiency above standard limits; instead, they reduce the quantity and quality of material necessary to approach those limits, allowing for substantial cost reductions. Additionally, nanowires provide opportunities to fabricate complex single-crystalline semiconductor devices directly on low-cost substrates and electrodes such as aluminum foil, stainless steel, and conductive glass, addressing another major cost in current photovoltaic technology. This review describes nanowire solar cell synthesis and fabrication, important characterization techniques unique to nanowire systems, and advantages of the nanowire geometry.

Plasmonic dye-sensitized solar cells using core-shell metal-insulator nanoparticles.

Abstract: We present an investigation into incorporating core−shell Au−SiO2 nanoparticles into dye-sensitized solar cells. We demonstrate plasmon-enhanced light absorption, photocurrent, and efficiency for both iodide/triiodide electrolyte based and solid-state dye-sensitized solar cells. Our spectroscopic investigation indicates that plasmon-enhanced photocarrier generation competes well with plasmons oscillation damping with in the first tens of femtoseconds following light absorption.

Synthesis of fluorinated polythienothiophene-co-benzodithiophenes and effect of fluorination on the photovoltaic properties.

Abstract: Herein, we describe the synthesis of fluorinated polythienothiophene-co-benzodithiophenes (PTBFs) and the characterization of their physical properties, especially their performance in solar cells. Fluorination of the polymer backbone lowered both the HOMO and LUMO energy levels and simultaneously widened the energy bandgap of the polymer (0.1-0.2 eV). Incorporation of fluorine into the various positions of the polymer backbone significantly affected the solar cells' power conversion efficiency from 2.3% to 7.2%. Detailed studies revealed that the polymer containing mono-fluorinated thienothiophene gave the best solar cell performance. Perfluorination of the polymer backbone led to poor compatibility with PC(71)BM molecules, thus poor solar energy conversion efficiency. This is possibly due to the enhanced self-organization properties of the polymer chains and the fluorophobicity effect. Furthermore, it was found that perfluorination of the polymer backbone resulted in poor photochemical stability against singlet oxygen attack. Theoretical studies indicated that the internal polarization caused enhancement of the negative charge density on thienothiophene rings, which rendered them vulnerable to [2+4] cycloaddition reaction with singlet oxygen.

Dye-Sensitized Solar Cells Based on

Abstract: Bismuth titanate (Bi4Ti3O12) particles were synthesized by hydrothermal treatment and nanoporous thin films were prepared on conducting glass substrates. The structures and morphologies of the samples were examined with X-ray diffraction and scanning electron microscope (SEM). Significant absorbance spectra emerged in visible region which indicated the efficient sensitization of Bi4Ti3O12 with N3 dye. Surface photovoltaic properties of the samples were investigated by surface photovoltage. The results further indicate that N3 can extend the photovoltaic response range of Bi4Ti3O12 nanoparticles to the visible region, which shows potential application in dye-sensitized solar cell. As a working electrode in dye-sensitized solar cells (DSSCs), the overall efficiency reached 0.48% after TiO2 modification.

Effects of Additives on the Morphology of Solution Phase Aggregates Formed by Active Layer Components of High-Efficiency Organic Solar Cells

Abstract: Processing additives are used in organic photovoltaic systems to optimize the active layer film morphology. However, the actual mechanism is not well understood. Using X-ray scattering techniques, we analyze the effects of an additive diiodooctane (DIO) on the aggregation of a high-efficiency donor polymer PTB7 and an acceptor molecule PC71BM under solar cell processing conditions. We conclude that DIO selectively dissolves PC71BM aggregates, allowing their intercalation into PTB7 domains, thereby optimizing both the domain size and the PTB7–PC71BM interface.

Optically transparent cathode for dye-sensitized solar cells based on graphene nanoplatelets.

Abstract: Commercial graphene nanoplatelets in the form of optically transparent thin films on F-doped SnO2 (FTO) exhibited high electrocatalytic activity toward I3−/I− redox couple, particularly in electrolyte based on ionic liquid (Z952). The charge-transfer resistance, RCT, was smaller by a factor of 5−6 in ionic liquid, compared to values in traditional electrolyte based on methoxypropionitrile solution (Z946). Optical spectra and electrochemical impedance confirm that the film’s absorbance scales linearly with RCT−1. Electrocatalytic properties of graphene nanoplatelets for the I3−/I− redox reaction are proportional to the concentration of active sites (edge defects and oxidic groups), independent of the electrolyte medium. Dye-sensitized solar cell (DSC) was assembled with this material as a cathode. Semitransparent (>85%) film of graphene nanoplatelets presented no barrier to drain photocurrents at 1 Sun illumination and potentials between 0 and ca. 0.3 V, but an order of magnitude decrease of RCT is still n...

Rare-earth ion doped up-conversion materials for photovoltaic applications.

Abstract: With the aim of utilizing the infrared region of solar radiation to improve solar cell performance, significant progress, including theoretical analysis and experimental achievement, has been made in the field of up-conversion for photovoltaic applications. This Research News article reviews recent progress in the development of rear-earth (RE) ion doped up-conversion materials for solar cell applications. In addition, new trends for RE-ion-doped phosphors are briefly discussed, among them trivalent RE-ion-doped up-conversion materials for organic solar cell applications.

Improving device efficiency of polymer/fullerene bulk heterojunction solar cells through enhanced crystallinity and reduced grain boundaries induced by solvent additives.

Abstract: Polymer solar cells based on bulk heterojunction (BHJ) structures, featuring conjugated polymers as donors and fullerene derivatives as acceptors, [ 1 ] are being developed for their potential application in the low-cost fabrication of large-area devices. In recent reports, BHJ solar cells incorporating crystalline or low-bandgap conjugated polymers [ 2 ] and fullerene derivatives have exhibited maximum power conversion effi ciencies (PCEs) of up to 8%. [ 3 ] The morphology [ 4 ] of the active layer in a BHJ solar cell incorporating a polymer/fullerene thin fi lm plays a critical role affecting the device performance; phase-separated domains in the active layer provide not only interfaces for charge separation of photogenerated excitons but also percolation pathways for charge carrier transport to the respective electrodes, critically affecting the device’s PCE. The nanoscale morphology of a polymer/fullerene thin fi lm is greatly affected by (i) the fi lm processing conditions, [ 5 ] (ii) the molar ratio (composition) of the polymer and the fullerene, [ 6 ] and (iii) the nature of the solvent additive (if any). [ 7 ] In particular, BHJ polymer solar cells can exhibit improved device performance after undergoing thermal or solvent annealing or the incorporation of solvent additives, all of which alter the fi lm morphology to a more favorable state relative to that of the as-cast fi lm or the fi lm in the absence of the additive, presumably resulting from (i) self-organization of the polymer units into ordered structures and (ii) appropriate aggregation of fullerene domains to provide percolation networks for charge carrier transport. [ 6 , 8 ] Among these approaches, the addition of solvent additive during the processing of the active layer is the simplest and most effective means of optimizing a BHJ device’s morphology; it infl uences the size of the fullerene domains and enhances the crystallinity of the self-organized polymers by improving the solubility of

Cu2S Reduced Graphene Oxide Composite for High-Efficiency Quantum Dot Solar Cells. Overcoming the Redox Limitations of S2–/Sn2– at the Counter Electrode

Abstract: Polysulfide electrolyte that is employed as a redox electrolyte in quantum dot sensitized solar cells provides stability to the cadmium chalcogenide photoanode but introduces significant redox limitations at the counter electrode through undesirable surface reactions. By designing reduced graphene oxide (RGO)-Cu2S composite, we have now succeeded in shuttling electrons through the RGO sheets and polysulfide-active Cu2S more efficiently than Pt electrode, improving the fill factor by ∼75%. The composite material characterized and optimized at different compositions indicates a Cu/RGO mass ratio of 4 provides the best electrochemical performance. A sandwich CdSe quantum dot sensitized solar cell constructed using the optimized RGO-Cu2S composite counter electrode exhibited an unsurpassed power conversion efficiency of 4.4%.

Infrared Colloidal Quantum Dots for Photovoltaics: Fundamentals and Recent Progress

Abstract: Colloidal quantum dots (CQDs) are solution-processed semiconductors of interest in low-cost photovoltaics. Tuning of the bandgap of CQD films via the quantum size effect enables customization of solar cells' absorption profile to match the sun's broad visible- and infrared-containing spectrum reaching the earth. Here we review recent progress in the realization of low-cost, efficient solar cells based on CQDs. We focus in particular on CQD materials and approaches that provide both infrared and visible-wavelength solar power conversion CQD photovoltaics now exceed 5% solar power conversion efficiency, achieved by the introduction of a new architecture, the depleted-heterojunction CQD solar cell, that jointly maximizes current, voltage, and fill factor. CQD solar cells have also seen major progress in materials processing for stability, recently achieving extended operating lifetimes in an air ambient. We summarize progress both in device operation and also in gaining new insights into materials properties and processing - including new electrical contact materials and deposition techniques, as well as CQD synthesis, surface treatments, film-forming technologies - that underpin these rapid advances.

Hierarchical nanomorphologies promote exciton dissociation in polymer/fullerene bulk heterojunction solar cells.

Abstract: PTB7 semiconducting copolymer comprising thieno[3,4-b]thiophene and benzodithiophene alternating repeat units set a historic record of solar energy conversion efficiency (7.4%) in polymer/fullerene bulk heterojunction solar cells. To further improve solar cell performance, a thorough understanding of structure-property relationships associated with PTB7/fullerene and related organic photovoltaic (OPV) devices is crucial. Traditionally, OPV active layers are viewed as an interpenetrating network of pure polymers and fullerenes with discrete interfaces. Here we show that the active layer of PTB7/fullerene OPV devices in fact involves hierarchical nanomorphologies ranging from several nanometers of crystallites to tens of nanometers of nanocrystallite aggregates in PTB7-rich and fullerene-rich domains, themselves hundreds of nanometers in size. These hierarchical nanomorphologies are coupled to significantly enhanced exciton dissociation, which consequently contribute to photocurrent, indicating that the nanostructural characteristics at multiple length scales is one of the key factors determining the performance of PTB7 copolymer, and likely most polymer/fullerene systems, in OPV devices.

Organic solar cells: A new look at traditional models

Abstract: Traditional inorganic solar cell models, originating with the work of Shockley, are widely used in understanding bulk heterojunction (BHJ) organic solar cell response (organic solar cells are also referred to as organic photovoltaics, or OPVs). While these models can be useful, there are several key points of departure from traditional solar cell behavior. In this Perspective, we discuss three important areas: (1) geminate pair and bimolecular recombination, (2) effects of interfacial layers inserted between the electrodes and active layer, and (3) resistance effects. Since organic solar cell materials typically have large Coulombic exciton binding energies (e.g., ∼0.3–0.5 eV), limited dissociation of photogenerated charge carriers can be a significant limitation in these cells that is not observed in traditional silicon solar cells. Additionally, the active layer morphology of BHJ organic solar cells allows free charge carriers to recombine before extraction from the cell, creating another photocurrent loss mechanism. Interfacial layers serve a unique role in BHJ organic solar cells; in addition to conventional functions such as photon transmission and charge injection, interfacial layers often act as “blocking” layers, ensuring that charge carriers are collected at their respective electrodes (i.e., electrons at the cathode and holes at the anode). Additionally, resistance effects in organic solar cells differ from traditional models in both field and cell area dependencies. Organic semiconductor mobilities and charge densities exhibit significant sensitivity to field strength, with mobility varying by ∼10x over typical cell voltage test ranges (1 V). This creates the need for alternative models to describe cell internal resistance. Finally, resistance losses are also sensitive to cell area, due to the limited conductivities of the transparent electrode materials used. Therefore, accommodation of the above deviations from traditional models is imperative for the design and synthesis of new generation high efficiency organic solar cell materials.

Tandem colloidal quantum dot solar cells employing a graded recombination layer

Abstract: Researchers report a colloidal quantum-dot solar cell that features two junctions, each designed to absorb and convert different spectral bands of light within the solar spectrum. The device offers a power conversion efficiency of 4.2% and an open circuit voltage of 1.06 V.

Large Integrated Absorption Enhancement in Plasmonic Solar Cells by Combining Metallic Gratings and Antireflection Coatings

Abstract: We describe an ultrathin solar cell architecture that combines the benefits of both plasmonic photovoltaics and traditional antireflection coatings. Spatially resolved electron generation rates are used to determine the total integrated current improvement under AM1.5G solar illumination, which can reach a factor of 1.8. The frequency-dependent absorption is found to strongly correlate with the occupation of optical modes within the structure, and the improved absorption is mainly attributed to improved coupling to guided modes rather than localized resonant modes.

Light Absorption Enhancement in Thin‐Film Solar Cells Using Whispering Gallery Modes in Dielectric Nanospheres

Abstract: Freely propagating sunlight can be diffractively coupled and transformed into several guided whispering gallery modes within an array of wavelength scale dielectric spheres. Incident optical power is then transferred to the thin-film cell by leaky mode coupling into a thin solar cell absorber layer and significantly enhances its efficiency by increasing the fraction of incident light absorbed.

Graphene nanoplatelets outperforming platinum as the electrocatalyst in co-bipyridine-mediated dye-sensitized solar cells.

Abstract: Graphene nanoplatelets (GNP) in the form of thin semitransparent films on F-doped SnO2 (FTO) exhibit high electrocatalytic activity for the Co(bpy)33+/2+ redox couple in acetonitrile electrolyte solution. The GNP film is superior to the traditional electrocatalyst, that is, platinum, both in charge-transfer resistance (exchange current) and in electrochemical stability under prolonged potential cycling. The good electrochemical performance of GNP is readily applicable for dye-sensitized solar cells with Y123-sensitized TiO2 photoanodes and Co(bpy)33+/2+ as the redox shuttle. The dye-sensitized solar cell with GNP cathode is superior to that with the Pt-FTO cathode particularly in fill factor and in power conversion efficiency at higher illumination intensity.

Upconverter solar cells: materials and applications

Abstract: Spectral conversion of sunlight is a promising route to reduce spectral mismatch losses that are responsible for the major part of the efficiency losses in solar cells Both upconversion and downconversion materials are presently explored In an upconversion process, photons with an energy lower than the band gap of the solar cell are converted to higher energy photons These higher photons are directed back to the solar cell and absorbed, thus increasing the efficiency Different types of upconverter materials are investigated, based on luminescent ions or organic molecules Proof of principle experiments with lanthanide ion based upconverters have indicated that the benefit of an upconversion layer is limited by the high light intensities needed to reach high upconversion quantum efficiencies To address this limitation, upconverter materials may be combined with quantum dots or plasmonic particles to enhance the upconversion efficiency and improve the feasibility of applying upconverters in commercial solar cells

Plasmonic polymer tandem solar cell.

Abstract: We demonstrated plasmonic effects in an inverted tandem polymer solar cell configuration by blending Au nanoparticles (NPs) into the interconnecting layer (ICL) that connects two subcells. Experimental results showed this plasmonic enhanced ICL improves both the top and bottom subcells' efficiency simultaneously by enhancing optical absorption. The presence of Au NPs did not cause electrical characteristics to degrade within the tandem cell. As a result, a 20% improvement of power conversion efficiency has been attained by the light concentration of Au NPs via plasmonic near-field enhancement. The simulated near-field distribution and experimental Raman scattering investigation support our results of plasmonic induced enhancement in solar cell performance. Our finding shows a great potential of incorporating the plasmonic effect with conventional device structure in achieving highly efficient polymer solar cells.

Colloidal Quantum Dot Photovoltaics: A Path Forward

Abstract: Colloidal quantum dots (CQDs) offer a path toward high-efficiency photovoltaics based on low-cost materials and processes. Spectral tunability via the quantum size effect facilitates absorption of ...

An Organic D-π-A Dye for Record Efficiency Solid-State Sensitized Heterojunction Solar Cells

Abstract: The high molar absorption coefficient organic D-pi-A dye C220 exhibits more than 6% certified electric power conversion efficiency at AM 1.5G solar irradiation (100 mW cm(-2)) in a solid-state dye sensitized solar cell using 2,2',7,7'-tetrakis(N,N-dimethoxyphenylamine)-9,9'-spirobi-fluorene (Spiro-MeOTAD) as the organic hole transporting material. This contributes to a new record (6.08% by NREL) for this type of sensitized heterojunction photovoltaic device. Efficient charge generation is proved by incident photon-to-current conversion efficiency spectra. Transient photovoltage and photocurrent decay measurements showed that the enhanced performance achieved with C220 partially stems from the high charge collection efficiency over a wide potential range.