The Third Generation of Photovoltaic devices · • Developapproachtowardsimprovingtransparent top...

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Veronica Bermudez, NEXCIS, France

The Third Generation of Photovoltaic devices

1. PV and its potential. Introduction

2. Present technologies in market

3. Innovative concepts towards nano-concepts

1. Ink nanoparticles: nanosolar

2. Electrodeposition: nexcis, solopower

Agenda

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4. Towards Third generation

1. Intraband concepts. CIGS case

2. Potential of advanced optics. CGS case

3. Nanostructured CdTe

5. Conclusions

When grid parity will be achieved -> demand will exceed offer => business with a big growthpotential

With a grid parity towards Gigawatts

Source: DB estimates

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In a system, cost are constituted from module cost and costrelated to the surface occupied by the system (installation, field,wires,,..) and cost related with efficiency (converter,…) y O&M

• So, the most important parameter of a PV system is efficiency, due to the

Cost definition


a PV system is efficiency, due to thefact that it is the cost driven throughmodules and field related costs

ZSW: 20.3%







Agenda







5. Conclusions

Thin film present efficiencies

CIS CdTe

Best cell, laboratory

20.3% 16,5%

Best module 15.7% 11%

Production 12% 10%

Module size (single substrate) 60 x120 cm2 and larger

Efficiency

Fabrication process


Fabrication process

CIS CdTe

Contact Sputtering Sputtering

Absorber Coevaporacion/Sputtering/ electrodepositionSelenization/Sulfurization

Close SpaceSublimación/evaporación(CSS)

Junction Chemicql BathDeposition (CBD)

CSS, activation

Patterning Laser, mechanical Laser, mechanical

Module Efficiency. Expectation of min/max values, driven by intensive R&D and innovations







Agenda







5. Conclusions

Generation III has the potential to achieve limiting efficiencies greater than the single junction limit.It is also expected that this technologies, which are still emerging, will also be able to achieve costs levels similar to or

Third generation for Thin Films


achieve costs levels similar to or better than Generation II technologies.

Efficiency vs. Eg

-Reflect best materials and process properties

-Needs further understandingof limitation at high Ga

-Understand the performance limitingmechanism


mechanism

-Bulk vs. Interface recombination

-Grain boundariescontribution

-Phase inhomogeneity

Why Wide-Gap?

Optimum gap for single junction cells

Challenge our understanding and models

Can use sulfides

Required for tandem cells

Top cell transparency in models, no reallyrealistic.


More work neede to undesrtand model and to identify process routes for highertransparency.

Calculated efficiency of tandem cells based on NREL 20% cell

• Develop approach towards improving transparent top cells, an appropriate bottom cell, and interconnect, toward a target > 25%-efficient polycrystalline thin-film tandem solar cell.

• Ultimate goal is monolithic tandem

• Using CIGS solar cells in tandem devices. The investigated or planned-to-investigate structures includeCGS/CIS, dye sensitized cell (DSC)/CIGS, a-Si/CIGS, as well as (DSC?)/CdTe(CI(G)S ) tandem cells.

Achieved (literature):•Bottom cell with Eg≈1.1 eV and η≈20%. •Tunnel contact TCO/Cu(InGa)Se2

To Do:•Top cell with Eg≈1.7 eV and η≈20%or at least 15%•Transparency > 70% for E < Eg

Real Tandem


•Transparency > 70% for E < Eg

•Low-temperature process for top cell (T < 200°C)•or Temperature-stable bottom cell(T > 450°C)•or New idea

Thin film tandem cell combining low cost thin-film technologywith highest efficiencies

Intraband concepts


Marti, et al , J. Appl Phys. 103, 073706 (2008)

Limiting efficiency of an IBSC when operated at 1 sun as a functionof the total semiconductor band gap EG. Figures in the plot indicate the optimum value in eV of the sub bandgap EL. The limiting efficiency of single gap solar cells is also shown for comparison dashed line, as well as the reported state of the art under AM1.5G of Cu-containing, chalcopyrite based solar cells

Intraband concepts


Limiting efficiency of a CuGaS2 solar cell as a function of the position of the IB measured from the CB or from the VB indistinguishably.The position of the energy level predicted for some transition elements is also indicated.

Predicted energy levels in CuGaS2 for different transition elements

Marti, et al , J. Appl Phys. 103, 073706 (2008)

Intraband concepts

Performance of CuInGaSe2


Current density-voltage characteristic of the same CuInGaSe2 solar cell, in the presence of non radiativerecombination when illuminated with AM1.5G spectrum AM1.5G-single gap, BB radiation at 6000 K (BB singleGap), when an IB is inserted (BB-IBSC) at its optimum position (EL=0.37 eV) and for the case in which the overlap between absorption coefficients exist.

Potential of advanced optics


Lipovsek, et al, Energy Procedia 2 (2010) 143-150

Several ways to improve efficiency

• Control of material synthesis at reduced costs

• New optical Engineering: concentration, photonic conversion,

• New materials and concepts, fitting of properties, electronic transport,…


Extraordinary perspectives:� Increasing of performance� Costs reduction

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