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A Cost-Effective Process for High-Quality Back Surface Passivation in Si Solar Cells

Proposal:. A Cost-Effective Process for High-Quality Back Surface Passivation in Si Solar Cells. Vichai Meemongkolkiat November 13, 2003. Outline. Objective Motivation Introduction Procedure Facilities requirements Timetable Work plan. Objective.

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A Cost-Effective Process for High-Quality Back Surface Passivation in Si Solar Cells

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  1. Proposal: A Cost-Effective Process for High-Quality Back Surface Passivation in Si Solar Cells Vichai Meemongkolkiat November 13, 2003

  2. Outline • Objective • Motivation • Introduction • Procedure • Facilities requirements • Timetable • Work plan

  3. Objective • To find a cheap and fast way to passivate the back surface of solar cells

  4. Motivation • For solar cells to be able to compete with other electricity sources, $/Watt needs to be reduced: • Improve efficiency • Reduce production cost • For high-efficiency cells, good back surface passivation is mandatory

  5. Light e- e- e- e- Introduction • Surface recombination velocity (SRV) is the figure of merit for passivation quality • Lower is better • Below 200 cm/s is decent Bulk Emitter Front Back p n+

  6. Procedure: 4 Steps Choose the basic passivation methods Achieve decent quality of passivation on each of the chosen methods Apply the methods on actual solar cells Assess SRV

  7. Choose the Basic Passivation Methods Step 1: • Three basic methods for passivation were chosen

  8. Achieve Decent Quality of Passivation on Each of the Chosen Methods Step 2: • Al-BSF • Method for uniform Al-BSF was established • SRV of 230 cm/s was obtained • Dielectric passivation • RTO/LF-SiNx provided the best passivation • SRV of 51 cm/s was obtained by RTO/LF-SiNx (without electrical contacts) • Boron-BSF • Results indicated promisingly low SRV

  9. (1) (2) (3) Al-BSF Al-BSF+Dielectric Boron-BSF+Dielectric Si solar cell Si solar cell Si solar cell Al-BSF Al-BSF Boron-BSF Metal Metal Metal Dielectric Dielectric Apply the Methods on Actual Solar Cells Step 3: • Three solar cells structures were proposed

  10. Step 4: Assess SRV • SRV can be obtained by measuring IQE and bulk lifetime SRV of the back surface Bulk lifetime Long-wavelength internal quantum efficiency (IQE)

  11. Facilities Requirements • Fabrication tools • Diffusion furnace • PECVD • RTP • Screen-printer • Belt furnace • Characterization tools • SEM • IQE system • PCD tool • PC1D simulation program • Resources • FZ wafers, boron-BSF sample, and screen-printing pastes

  12. Timetable

  13. Work Plan • Completed tasks • Chose the three basic passivation methods • Designed the three solar cells structures • Fabricated solar cells with Al-BSF structure and acquired the SRV • Decided the type of dielectric to be used • Acquired promisingly low SRV using boron-BSF • Remaining tasks • Establish the fabrication processes for the two remaining structures • Fabricate and characterize the remaining structures to obtain SRV • Compare all the structures in terms of electrical quality and cost-effectiveness

  14. Questions?

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