DuPont: Enable Next Generation High Efficiency Solar Cells (Aug 2013)

DuPont™ Solamet®

Enable Next Generation High Efficiency

Solar Cells

Dr. Alex Wu

Technology Manager, Taiwan

DuPont Microcircuit Materials

Aug. 16, 2013

© E. I. DuPont 2013

Eff

icie

ncy (

%)

Year

Conventional Cells Solamet® PV14x Products

High Efficiency Cells Solamet® PV15x, 16x

High Efficiency LDE Cells

Solamet® PV17x, 18x

New LBSF

(LDE) Architectures Solamet® PV36x

N-type Cell Bi-facial: PV3Nx

IBC: Pv197

Back Contact MWT : Solamet® PV70x

Cell Efficiency Evolution

2


Broad Capabilities Under One Roof

Design, fabrication, and characterization of advanced cell and module architectures

DuPont invest to support long-term industry growth.

3


What’s the Main loss of Crystalline Si PV? Loss in Currents

4

• Jmax: Theoretical maximum for a

certain wafer thickness

• Jgen: Generated photo-current in

actual device

1. Optical loss= Jmax- Jgen

2. Recombination & Resistive losses

= Jmpp-Jgen


Eff (%) 18.7 19 20 19.7 23

Voc (mV) 633 643 651 648 699

Cell Structure and Efficiency Evolution

N-ty

pe IB

C

N-ty

pe Bi-fac

ial

P-ty

pe P

ERC

P-ty

pe LDE

P-ty

pe S

TD

N-typ

e IBC

N-typ

e Bi-fa

cial

P-ty

pe P

ERC

P-ty

pe LDE

P-ty

pe S

TD

44

43

42

41

40

39

38

37

36

35

Cu

rre

nt

De

nsit

y (

mA

/cm

2)

ΔJ optical

ΔJ front

ΔJ Auger, base

ΔJ SRH, base

ΔJ rear

J mpp

Jmax

High-efficiency Silicon Solar Cells

Stefan Glunz

Fraunhofer Institute for Solar Energy Systems ISE 5


Achieving higher solar cell efficiency with advanced

materials and technology

Fine line and MWT

Local Back Surface Field

N-type bi-facial

Interdigitated Back Contact

6

© E. I. DuPont 2013 7

Reduce the Optical Loss: Fine Line Print

Squeegee side Wafer side

44 um 40 um

46 um 46 um

Fine Line Print


Reduce the Optical Loss: MWT and Solamet ® PV70x

reference PV70x

8


Options 1:

Options 2:

MWT Module Assembly Options

• PCB as backsheet foil and ECA to connect

• High cost

• Cu foil and patterning process

• ECA

• Tab-string (manually or automated)

• Bowing and yield loss

9


Reduce Rear Side Recombination: LBSF (PERC)

p-type Si

p+

Al paste PV36x

SiO2 or Al2O3

FS-Ag paste

PV17x / PV18x

SiNx

i-PERC major advantage

- Minimized surface recombination velocity (SRV)

- Increased internal reflectivity

- Higher Voc, Jsc, and cell efficiency (up to 1%)

Other advantages

- Minor change in the cell/module production

- Necessary for thin wafers (<150um)

10


Surface Recombination Velocity and Types of Passivation

11


+++++++++++++

P+

Induced n-type layer

+++++++++++

- - - - - - - -

P+

Al2O3 or SiO2 layer

Rear Shunting Issue and iPERC Solution

Direct Al L-BSF firing

with SiNx passivation iPERC p type p+ type

n type n+ type

SiNx SiO2 or Al2O3 Metal

Positive charges in SiNx

induce n-type layer at the

rear interface.

Direct metal contact to both

p-type local BSF and induced

n-type layer creates shunted

junction → no BSF effect.

Negative charge in the Al2O3

or SiO2 layer, together with

the increased distance of the

SiNx layer from the surface,

prevent formation of induced

n-type layer.

12


Internal Reflection and Quantum Efficiency

Light absorbed Reflected light will generate

additional current

Standard Cell Local BSF Cell

13


DuPont™ Solamet® PV36x for Local BSF

Strong adhesion to passivation and reliable module performance

Innovation in glass and Al powder technology for better contact

Reference PV36x

Al

Si

Al

Si

PV36x Reference

14


406 nm 655 nm 875 nm 975 nm

PV

505

PV

56S

LBIC Test

•PV56S shows less passivation damage than PV505

(Width: Busbar=1.8 mm, Tabbing= 6 mm)

Solamet® PV56S for PERC BS Tabbing

15

© E. I. DuPont 2013 16

LID Issue for LBSF on Multi?

27th European Photovoltaic Solar Energy Conference and Exhibition

Light Induced Degradation of Rear Passicvated mc-Si Solar Cells

K. Ramspeck, S. Zimmermann, H. Nagel, A. Metz, Y. Gassenbauer, B. Birkmann, A. Seidl

mc-PERC

mc-BSF

mono-PERC

mono-BSF

© E. I. DuPont 2013 17

p+-Si (B-doped emitter)

n-Si (base)

n+-Si (P-doped BSF)

n+-Si (P-doped FSF)

n-Si (base)

p+-Si (B or Al-doped emitter)

Rear emitter N-cell

Rear p-contact (Ag/Al or Al)

Front p-contact (Ag/Al)

Rear n-contact (Ag)

Front n-contact (Ag)

Multiple options

• Front emitter or rear emitter

• Textured or planar rear

• SiO2/SiNx or Al2O3/SiNx passivation

• (BBr3, BCl3)/POCl3 diffusion, ion implantation, or other

• Lightly-doped emitter (LDE) and LD-BSF(FSF)

N-type Bi-facial

Front emitter N-cell


DuPont™ Solamet® PV3N1: for N-type Bi-facial Cell

PV17x/PV18x

18

© E. I. DuPont 2013 19

IBC (Interdigitated Back Contact)


DuPont™ Solamet® PV197: for IBC

Current paste system for IBC

Electrode for n+ : Ag paste

Electrode for p+ : Al or Ag/Al paste

Firing temp. : >750degC

DuPont paste for IBC

IBC paste system

Electrode for n+ :

Electrode for p+ :

Firing temp. : 550-600degC

Minimum damage to BS passivation.

Minimum thermal damage to Si.

Less wafer bowing.

Good solder process compatibility.

p+ p+ p+ n+ n+ n+

One paste system

How to minimize wafer bowing ?

How to make tabbing by solder ribbon ?

20


New

A

rch

itec

ture

s IB

C

MW

T

N-t

ype

Bac

k

Rea

r Ta

bb

ing

Al S

yste

ms

Fro

nt

Sin

gle

Pri

nt

h

igh

ad

hes

ion

2010 2011 2012 2013 2014 2015 2016

Solamet® Product Generation Road Map

Front side contact Rear contact Interconnect Interconnect

Double Print PVD2A

Non-fire through Ag Contacts for Gen 1/2 LBSF structures

PV17X for HE/LDE

Low Cost Alternative metal interconnect

Local Back Surface Field Al PV36X (Laser Ablated)

IBC Metallizations

Metallizations for decoupled interconnect (Dual Print) PVxxx

Full Plane back surface field Al

PV16A

PV18X for LDE +

PV19X for LDE ++

Improved performance, driving down consumption, improved adhesion & fine line capability

PV1XX Pb free

Low cost tabbing interconnects PV51X and PV52X

Low cost high adhesion non-fire through interconnect tabbing Ag

MWT Via Gen 1 : PV701

MWT Via Gen 1 : PV7xx reduced shunting

N-type : p-contact PV3N1

N-type : p-contact PV3NX – higher conductivity, lower contact & low Voc loss

Front side metallizations based on alternative metals

Gen 2 Lower CoO LBSF structures

Improving yields, reduce linewidth, maximize adhesion

Mu

ltip

le

pri

nt

21


• 20% cell has been realized in production

• The path to 22% is clear but needs…

• More cooperation between cell and module

• Simple and cost effective technology

• Innovative and integrated material solution, i.e. DuPont DPVS

• DuPont will continue to lead and invest the technology to realize high

efficiency with low CoO in both PV cell and module production

• We commit to achieve 22% in 2015

mcm.dupont.com

Summary

22

http://www2.dupont.com/MCM/en_US/products/photovoltaic_metallizations.html

Copyright © 2013 DuPont or its affiliates. All rights reserved. The DuPont Oval Logo, DuPont™, The miracles of science™ and all products denoted with ™ or ® are registered trademarks or trademarks of E. I. du Pont de Nemours and Company or its affiliates.

Images reproduced by E. I. du Pont de Nemours and Company under license from the National Geographic Society.

photovoltaics.dupont.com

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DuPont: Enable Next Generation High Efficiency Solar Cells (Aug 2013)

Engineering