Meeting 2014-October WP1 INL :. 2 -1. Simulation for Laser Interference Lithography sample (PI32) -2. Possible alternative: patterning of the front electrode

Meeting 2014-October

WP1 INL :

2

- 1. Simulation for Laser Interference Lithography sample (PI32)

- 2. Possible alternative: patterning of the front electrode only, not of the active layer

- 3. Double side patterning: back side patterning at ZnO/Ag interface, instead of the cSi/ZnO interface

- 3. Multiperiodic pattern on thin film

INL : Outline

3

I: Simulati on for Laser Interference Lithography sample (PI32)

- One of the goal of WP1 :

Determine the optimized nanopattern for solar cells

- FDTD simulation:

determination of the optical absorption in the PECVD Si layer

estimation of the potential Jsc

PECVD Si

n doped Si substrate

Vertical stack under consideration

See WP2 for LIL

4


- Description of the stack :

- FDTD simulation:

determination of the optical absorption in the PECVD Si layer only

PECVD Si


p

2re

PECVD Si


H1.5µm

At the beginning: At the end :

aSi (20nm)

ITO (50nm) only 10nm on vertical sidewall

See WP2 for LIL

5


- Optimal PC parameters :

p=450nm, e=150nm, r=140nm

Jsc = 13.5mA/cm²

p=600nm, e=200nm, r=215nm

Jsc = 13.7mA/cm²

- Experimental results:

Experimental deviation from the optical target…

Update of the optical simulation based on the experimental structure

PECVD Si


p

2re

aSi (20nm)


See WP2 for LIL

6


- Experimental PC parameters :

p=450nm, e=100nm, r=130nm

Jsc = 13.0mA/cm²

p=450nm, e=150nm, r=175nm

Jsc = 13.4mA/cm²

p=600nm, e=180nm, r=205nm

Jsc = 13.6mA/cm²

nb: without back interface, no Slow Bloch modes so no oscillations in the absorption spectrum

PECVD Si


p

2re

aSi (20nm)


See WP2 for LIL

• Nanopatterning induces electrical defects

- Wet etching seems to be better than Dry etching: we focus us on inverted pyramid design.

- But lifetime is still divided by a factor 2.

- Can we define an efficient light trapping design without adding electrical defects?

2. Possible alternative: patterning of the front electrode only

ITO

200 nm

RIE on PI32 sampleSEM from LPICM

- Comparison between patterned active layer and patterned TCO for an EPIFREE configuration :

Jsc = 14.0mA/cm² Jsc = 11.8mA/cm²

Can the optical losses be compensated by electrical gain?

2. Possible alternative: patterning of the front electrode only

aSi 25nm

ITO 75nm

cSi 1.1µm

Al

-15%

cSi 1.1µm

Al

NB: Approach considered in D1.6 Modelled Potential of double-side patterning

3. Double side patt erning: back side patt erning at ZnO/Ag interface, instead of the cSi/ZnO interface

cSI 6µm

BSF 100nm

Ag (opt. thick)

ITO

ZnO

aSi

cSI 6µm

BSF 100nm

Ag (opt. thick)

ITO

ZnO

aSi

cSI 6µm

BSF 100nm

Ag (opt. thick)

ITO

ZnO

aSi

ITO

Multilayer: Front pattern : Double-side pattern:

- Almost the same relative enhancement between front and dual pattern for 1D and 2D structure.

3. Double side patterning: back side patterning at ZnO/Ag interface, instead of the cSi/ZnO interface

Structure Jsc (mA/cm²) Abso. Rel.

multilayer 27.51D PC front pattern 31.7 +15.2% +15.2%1D PC dual pattern 33.1 +20.4% +4.5%2D PC front pattern 33.3 +22.1% +22.1%2D PC dual pattern 34.5 +26.3% +3.4%

cSI 6µm

BSF 100nm

Ag (opt. thick)

ITO

ZnO

aSi

NB: all the results are given after optimization

Jsc of the dual-side pattern cell correspond to the Jsc of a 23µm thick flat cell

- Thickness enhancement factor is more than 3!

3. Double side patt erning: back side patt erning at ZnO/Ag interface, instead of the cSi/ZnO interface

Si thickness of a flat cell

Jsc

(mA

/cm

²)cSI 6µm

BSF 100nm

Ag (opt. thick)

ITO

ZnO

aSi

- Linked to the deliverable Optimal Cell Designs (D1.8) :

- Can be used as supplementary information (or input) for the deliverable Experimental Non-Periodic Pattern films (D2.5) :

- Preliminar step on a simple design :

- Why this design?

only few optical modes

4. Multiperiodic pattern on thin-film

200nm aSi:H

glass

- Determination of the best periodic PC parameters :


nb: max. Jsc = 24mA.cm²

200nm aSi:H

glass

p=345nmff=0.50 (r=138nm)

FOM=58.76%

p=420nmff=0.39 (r=148nm)

FOM=56.52%

p=340nmff=0.50 (r=136nm)

FOM=58.65%

Square lattice of air holes Hexagonal lattice « Kagome » lattice

FOM=1 (full optical absorption)

- Particle Swarm Optimization on 2x2 supercell :

- The optimization lead to a design which is almost unperturbed …


p=345nmff=0.50

FOM=58.76%

Square lattice

period (p) from 300 to 400nmFilling factor (ff) from 0 to 1

hole shift (dx) from 0 to period 3 different parameters

2 x period

p=386.4nmff=0.7165dx=0.4917

FOM=62.37%


200nm aSi:H

glass



but the FOM is clearly dependant on distance between holes




2 x period

p=386.4nmff=0.7165dx=0.4917

FOM=62.37%


200nm aSi:H

glass



but the FOM is clearly dependant on distance between holes

and the FOM is non-robust in regard to the filling factor




2 x period

p=386.4nmff=0.7165dx=0.4917

FOM=62.37%


200nm aSi:H

glass



p=345nmff=0.50

FOM=58.76%

Square lattice

period from 325 to 375nm

ff from 0.2 to 0.8 (3 different values)

hole shift from 0 to period (2 different values)

6 different parameters

3 x period


200nm aSi:H

glass


- For this thin film configuration, the optimized design exhibit an absorption which is 2% higher than the unperturbed design.


Square lattice

FOM=60.29%

p=345nmff=0.50

FOM=58.76%


200nm aSi:H

glass

Conclusion and perspectives

- 1. Simulation for Laser Interference Lithography sample (PI32):

- see experimental nanopatterns in WP2 presentation

- see electrical results in WP3?

- 2. Active layer without pattern:

- lower optical absorption but without adding electrical defects

- 3. Multiperiodic nanopattern on thin-film:

- can increase the optical absorption

- thicker realistic multilayer system (with back metal, TCO, …) need to be considered

nanophotonics for ultra-thin crystalline silicon photovoltaics

project 309127

Documents

Meeting 2014-October WP1 INL :. 2 -1. Simulation for Laser Interference Lithography sample (PI32) -2. Possible alternative: patterning of the front electrode