Cu(In,Ga)Se 2 mesa microdiodes: study of edge recombination and behaviour under concentrated sunlight

ABSTRACT In order to develop photovoltaic devices with increased efficiency using less rare semiconductor materials, the concentrating approach is applied on Cu(In,Ga)Se2 thin film devices. For this purpose, Cu(In,Ga)Se2 microcells with a mesa design are fabricated. The influence of the edge recombination signal is analyzed. It is found that with an appropriate etching procedure, devices as small as 50x50 µm do not experience edge recombination efficiency limitations. Under concentration, significant Voc gains are seen, leading to an absolute efficiency increase of two points per decade

Structural and optical properties of (In,Ga)As/GaP quantum dots and (GaAsPN/GaPN) diluted-nitride nanolayers coherently grown onto GaP and Si substrates for photonics and photovoltaics applications

San Francisco, California, United StatesInternational audienceLattice-matched GaP-based nanostructures grown on silicon substrates is a highly rewarded route for coherent integration of photonics and high-efficiency photovoltaic devices onto silicon substrates. We report on the structural and optical properties of selected MBE-grown nanostructures on both GaP substrates and GaP/Si pseudo-substrates. As a first stumbling block, the GaP/Si interface growth has been optimised thanks to a complementary set of thorough structural analyses. Photoluminescence and time-resolved photoluminescence studies of self-assembled (In,Ga)As quantum dots grown on GaP substrate demonstrate a proximity of two different types of optical transitions interpreted as a competition between conduction band states in X and Γ valleys. Structural properties and optical studies of GaAsP(N)/GaP(N) quantum wells coherently grown on GaP substrates and GaP/Si pseudo substrates are reported. Our results are found to be suitable for light emission applications in the datacom segment. Then, possible routes are drawn for larger wavelengths applications, in order to address the chip-to-chip and within-a-chip optical interconnects and the optical telecom segments. Finally, results on GaAsPN/GaP heterostructures and diodes, suitable for PV applications are reporte

Cathode engineering with perylene-diimide interlayer enabling over 17% efficiency single-junction organic solar cells

In organic solar cells (OSCs), cathode interfacial materials are generally designed with highly polar groups to increase the capability of lowering the work function of cathode. However, the strong polar group could result in a high surface energy and poor physical contact at the active layer surface, posing a challenge for interlayer engineering to address the trade-off between device stability and efficiency. Herein, we report a hydrogen-bonding interfacial material, aliphatic amine-functionalized perylene-diimide (PDINN), which simultaneously down-shifts the work function of the air stable cathodes (silver and copper), and maintains good interfacial contact with the active layer. The OSCs based on PDINN engineered silver-cathode demonstrate a high power conversion efficiency of 17.23% (certified value 16.77% by NREL) and high stability. Our results indicate that PDINN is an effective cathode interfacial material and interlayer engineering via suitable intermolecular interactions is a feasible approach to improve device performance of OSCs

Le solaire photovoltaïque dans les transitions énergétiques et environnementales

Engineering schoolAvec 1 TW de capacité installée et 4% de la production mondiale d'électricité actuellement, l'énergie photovoltaïque aborde son stade de maturité. L'exposé fera d'abord un bref rappel de l'histoire du développement de l'énergie solaire, avec l'objectif de donner ses caractéristiques, son principe de fonctionnement, l'état de l'art technologique et des développements industriels.Nous aborderons dans un deuxième temps les grands défis de la filière pour contribuer aux transformations sociales, économiques et aux solutions dans la transition environnementale en cours, avant d'aborder au final les grands programmes d'investissement et les perspectives de la recherche scientifique.Nous essayerons de répondre à plusieurs questions : Qu'en est-il du caractère environnementalement vertueux de l'énergie solaire? Est-ce une énergie susceptible de contribuer de manière importante à la transition énergétique, malgré son caractère non pilotable? Quelles sont les évolutions techniques qui peuvent être attendues

Upconversion of 1.54

Upconverted emission from erbium ions in fluoride materials (glass and disordered crystal of the system CaF2-YF3) are observed in a wide spectral range (from the visible to the near infrared) under infrared excitation at 1.54 μm. In both cases, the upconverted emission in the near infrared (~1 μm) dominates the spectrum. Absolute UC efficiency defined as the ratio between the UC luminescence power and the absorbed pump power has been experimentally measured. The NIR (~1 μm) luminescence energy yield for the glass and the disordered crystal varies from 2.4 to 11.5% for the glass and from 7.7 to 16% for the crystal for an infrared excitation power density ranging from 2 W/cm2 to 100 W/cm2. This is of a particular interest for their use as upconverter to improve the c-Si cells quantum efficiency since the energy of the excitation lies below the c-Si absorption edge (1.12 eV at 300 K) and is well located compared to the AM1.5G solar spectrum, outside of the absorption lines due to different atmospheric gases. Furthermore, the most efficient upconverted emission recorded in the investigated materials occurs at an energy just above the gap. A current generated in a bifacial c- Si solar cell is observed when the Er3+ doped material (1.55 mA and 2.15 mA for the glass and the crystal respectively), placed at the rear face of the cell, is excited at 1.54 μm. The current dependence as a function of the sub-bandgap excitation power has been measured and modelled. Finally the EQE of the complete device is deduced from the measured short-circuit current and the incident photon flux on the cell. An increase of the cell quantum efficiency of 2.4% and 1.7% is obtained at 1.54 μm with adding the glass and the crystal respectively at the rear face of the c-Si cell. The results are compared to those already obtained with Er: NaYF4 known as the most efficient upconverter

Ferromagnetic Compounds for High Efficiency Photovoltaic Conversion: The Case of AlP:Cr

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Towards improved photovoltaic conversion using dilute magnetic semiconductors (abstract only)

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