effective efficiency of busbarless solar cells...effective efficiency of busbarless solar cells p....

Effective Efficiency of Busbarless solar cells P. Papet1, J. Levrat2, N. Bassi3, Y. Yao4, A. Waltinger5, V. Fakhfouri3, T. Soderstrom4, B. Strahm1

1 Meyer Burger Research, Hauterive, Switzerland.

2 CSEM PV-Center, Neuchâtel, Switzerland.

3 Meyer Burger (PASAN), Neuchâtel, Switzerland

4 Meyer Burger AG, GWATT, Switzerland

5 Meyer Burger (Germany), Hohenstein, Germany

[email protected]

Table of contents

2

Features SWCT

GRIDTOUCH measurement unit

Summary

Effective efficiency

Why the effective efficiency

Validation

Table of contents

3

Features SWCT


Summary



Validation

Evolution of Cell Connection Technology

4

Towards higher module power output

with less silver consumption

? ? ?

Cell with 3 BB Cell with 5 BB Cell with SWCT

SmartWire Connection Technology (SWCT)

5

Innovative and patented Foil-

Wire Electrode Concept

Multiple wires are used instead

of conventional cell connectors

(tab ribbons)

Compatible with HJT, PERC,

PERT, thin wafer and bifacial

cells

Higher module power

up to +6%1)

Higher energy yield up to 15%2)

Up to 83% less silver

in cell production1)

1) with HJT/SWCT compared to 3BB

2) with HJT/SWCT GG bifacial compared to 3BB

Better tolerance to

micro cracks

$/kWh

Fast track certification

Table of contents

6

Features SWCT


Summary



Validation

GRIDTOUCH measurement unit (GT)

7

Electrical Contacts

• Front Side : 30 current wires and 5 voltage wires

• Back Side :

• Grid Touch : up to 30 current wires and 5 voltage wires

• PCB Touch : PCB with up to 30 current track and 5 voltage tracks

Optics :

• no alteration of the light spectrum & intensity

• Different back reflectance available with PCB Touch version

Temperature :

• IR sensor

System & procedures approved and used at ISE CalLab

Compensation of the contacting unit shading

8

• By definition, shading of the contacting units is

not included in the solar cell performances

• Accredited method : measure with different

number of front wires and extrapolate the real Isc

of solar cell without wires.

• Practically : use a BBless reference cell for

calibration

Current measured on BBless cell is typically

higher than for a BB cell when same cell

technology used

BB cell case : schematic cross-section

Fingers Busbars

Substrate

Contacting bars

Fingers GT wires

BB0 cell case : schematic cross-section

Best number of contacting wires

9

Contact interface for BB cell is the Busbar and for a BBless cell the fingers.

The number of probes should be sufficient to satisfy accuracy and precision

Usually we desire no ohmic losses from the contact interface

Large number of pogo pins to avoid ohmic losses along BB for BB cell measure

Measured fill factor as function of the number of wires in the

GRIDTOUCH configurations.

• With 30 current wires, tested cells show

accurate & precise FF

• valid for Grid Resistance below 20ohm/m

• In accordance with ISE CalLab standard

Official way to measure BBless cell performances (GT efficiency)

Table of contents

10

Features SWCT


Summary



Validation

Why do we need the effective efficiency

11

Hypothesis:

- SWCT: 18 wires/250um

- 3BB: 3tabs/1500um

- 3BB/SWCT Shadow: 2.9%

- Cell area: 244 cm2 𝐂𝐓𝐌 − 𝐋 =𝐏𝐦𝐚𝐱−𝐜𝐞𝐥𝐥 − 𝐏𝐦𝐚𝐱−𝐞𝐧𝐝

𝐏𝐦𝐚𝐱−𝐜𝐞𝐥𝐥

Example with only interconnector shading effect

CTM-L equation : - Finger, wire & tabs ∞ conductive

- Encapsulation losses: 2% on Pmax

ᵑGT : BB0 measured with GT

ᵑCB : BB measured with Contacting Bars

Why do we need the effective efficiency

Example with only interconnector shading effect

Reduced process cost

Increased cell efficiency

Necessity to have an intermediate and “BB-equivalent” efficiency definition

Effective efficiency (eff)

Unfair cell price based on $/Wp for BB

cells, Increased CTM losses

Table of contents

13

Features SWCT


Summary



Validation

Effective efficiency First parameter: interconnector shading

Hypothesis:


- 3BB: 3tabs/1500um

- 3BB/SWCT Shadow: 2.9%

- Cell area: 244 cm2

- Finger, wire & tabs ∞ conductive

Hypothesis:

- Encapsulation losses: 2% on Pmax

ᵑGT : BB0 measured with GT

ᵑCB : BB measured with Contacting Bars

ᵑeff : BB/BB0 calculation

Interconnector

shading

Effective efficiency First parameter: interconnector shading

Reduced process cost

Same Efficiency Same cell efficiency

Same CTM losses

Close value between BBless effective efficiency and BB cell efficiency (contacting bar)

Positive for both manufacturers

Effective efficiency second parameter : the grid resistance

16

Busbar cell case BBless cell case

Busbar to Busbar resistance parameter is widely

used to characterize cells.

• Average finger resistance

• Evaluate the finger ohmic losses

For BB cell, fingers resistance influence cell

performances at LIV and in module

BBless measure is by definition not influenced by finger

resistance.

• True for the GT up to 20Ohm/m

However, in the module, finger resistance depend of number

of interconnectors used (12/15/18/36…)

Implement the finger ohmic losses based on the future

module interconnection design

• Grid resistance on front & back side are the key

values

• As for BB cell performances, finger ohmic losses

are inherent in the BBless effective efficiency

We define the Grid resistance as :

GR=𝑹𝑩𝑩𝒕𝒐𝑩𝑩

𝑳𝑩𝑩 𝒕𝒐 𝑩𝑩 =

𝑅𝑓𝑖𝑛𝑔𝑒𝑟𝑠

𝐿𝑓𝑖𝑛𝑔𝑒𝑟𝑠 [𝑂ℎ𝑚. 𝑚−1]

L : Distance

depends on nb of

wires in module

17

Effective efficiency second parameter : the grid resistance

Hypothesis:


- Cell area: 244 cm2

- Back fingers & wires ∞ conductive Interconnector

shading Finger resistance

effect

Effective efficiency :

• Gives the real potential of the cell in the specific module : CTM & $/Wp

• Efficient parameter for cell sorting and cell process optimizations

18

Effective efficiency practical calculation

BBless efficiency - ᵑGT

Grid resistance : GRf & GRb

Interconnection number &

size : Nsw & Dsw

Equations Effective efficiency - ᵑeff

Table of contents

19

Features SWCT


Summary



Validation

20

Effective efficiency : practical validation

Special R&D HJT BBless cells :

• Same front grid shading (Isc)

• Varia front Grid Resistance

• GRb = cte =2Ohm/m

Module integration :

• SWCT 18W200

• 16 cells module

CTM-L based on Effective efficiency

is independent of finger resistance

CTM-L is closer than typical value

with BB cells

Bifacial SWCT HJT Module performances

21

1000 modules produced power between 300-320W (with black backsheet)

Pmax

[W]

Voc

[V]

Isc

[A]

FF

[%]

White Backsheet 330 44.5 9.5 78.5%

Black Backsheet 320 44.4 9.1 79.5%

Power distribution

1000 modules (front side

illumination only and black

backsheet reflector)

Table of contents

22

Features SWCT


Summary



Validation

SWCT is mature module technology

>200MWp module installed

327Wp with 60 cells record module

Certification IEC & UL fast track

Busbarless cells measured with GRIDTOUCH contacting unit

System & method approved and available at ISE CalLab for independent validation

Effective efficiency : practical method to evaluate BBless cell performances based on module design

Efficient way for cell and module maker to improve their products

Feature available on Meyer Burger cell sorter

Conclusions

23

Pogo pins CTM Ribbon GT CTM SWCT GT_effective CTM SWCT

Fingers shading incl. on air effective shading incl. on air effective shading incl. on air effective shading

F & B finger ohmics

measured at

BB position

includedno extra losses

Not included affected

GT measure +

finger ohmics

losses

estimation

no extra losses

Wires/ribbons shading

BB shading

close to future

ribbon shading

included

no extra lossesNot included

wires cover cell

extra shading /

GT

GT measures +

SWCT wire

shading effect

estimation

no extra losses

Ribbons/wires ohmics Not included CTM Not included CTM Not included CTM

Optics (glass, encapsulant..) Not included CTM Not included CTM Not included CTM

BB cell BBless cell-GT BBless cell_GTeffLosses

High-end solutions for high-tech industries

effective efficiency of busbarless solar cells...effective efficiency of busbarless solar cells p....

Documents