ECE 695 Numerical Simulations Lecture 17: Transfer Matricespbermel/ece695/... · ECE 695 Numerical...

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ECE 695 Numerical Simulations Lecture 30: Finite-Difference Time Domain in MEEPPV Prof. Peter Bermel March 31, 2017

Transcript of ECE 695 Numerical Simulations Lecture 17: Transfer Matricespbermel/ece695/... · ECE 695 Numerical...

Page 1: ECE 695 Numerical Simulations Lecture 17: Transfer Matricespbermel/ece695/... · ECE 695 Numerical Simulations Lecture 30: Finite-Difference Time Domain in MEEPPV Prof. Peter Bermel

ECE 695Numerical Simulations

Lecture 30: Finite-Difference Time Domain in MEEPPV

Prof. Peter Bermel

March 31, 2017

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Si thin film

2 μm

PhC thin film

2 μm

silicon

aluminum

Wafer cell

200 μm

silicon

glass

Example: Simulating Si PV Absorption

Absorbed

Lost energy

Absorbed

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Different Geometric Light Trapping Approaches for Commercial mc-Si Cells

M.J. Keevers et al., “10% Efficient CSG Minimodules,”

Treatment #1 Sand blast Abrasion etch Bead coat

Treatment #2 HF etch HF etch (used in our samples)

Feature

depth

10-100 mm 500 nm 500 nm

Feature width 10 mm 1-5 mm 500 nm

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Correlated Randomness

Combine periodicity with texturing in systematic fashion

A.N. Bloch & P. Sheng, US Patent 4,683,160 (1987)

X. Sheng et al., Opt. Express 19, A841 (2011)

Combine gratings for each wavelength

inhomogeneous homogeneous

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Correlated Randomness in 2D

For n=3.46 and 33% bandwidth (e.g., 500-700 nm)

ECE 695, Prof. Bermel3/31/2017 5

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Angle-Sensitive Solar Absorbers

X. Sheng et al., Opt. Express 19, A841 (2011)

X. Wang et al., "Approaching the Shockley-Queisser Limit in GaAsSolar Cells", IEEE J. Photovolt. (2013).

ECE 695, Prof. Bermel3/31/2017 6

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-

From flat to totally random structures via correlated random textures

Keevers, M. J., et al. “10% efficiency CSG minimodules.” Proceedings of the 22nd European Photovoltaic Solar Energy Conference. (2007).

Higher correlation Lower correlation

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Experimental absorption versus simulated absorption

L. T. Varghese, Y. Xuan, B. Niu, L. Fan, P.

Bermel, and M. Qi, “Enhanced photon

management of thin-film silicon solar cells using

inverse opal photonic crystals with 3d photonic

bandgaps,” Advanced Optical Materials 1, 692–

698 (2013).

Experiment Simulation (3D QCRF-FDTD) SiO2

Silver

c-Si

ITO

H. Chung, K-Y. Jung, X. T. Tee, and P. Bermel,

"Time domain simulation of tandem silicon solar

cells with optimal textured light trapping enabled

by the quadratic complex rational function," Opt.

Express 22, A818-A832 (2014).

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Solar cell

schematic

MEEPPV: https://nanohub.org/tools/meeppv

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Output

animations

MEEPPV: https://nanohub.org/tools/meeppv

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MEEPPV: https://nanohub.org/tools/meeppv

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MEEPPV: https://nanohub.org/tools/meeppv

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Computational Set-up

• Thickness of film = our experimental samples (1.47 mm)

• Four geometries tested

• Random texturing:

– Uniform height distribution over 500 nm

– Distance between features varies

• Photonic crystal:

– Reflection captured by metal

– Diffraction captured by grating (optimized for this thickness)

texturing silicon metal

grating

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Varying spacing between features

5 periods

10 periods

20 periods3/31/2017ECE 695, Prof. Bermel

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Propagation of Light in Planar Geometry

Light In

Silicon

Metal

backing

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Propagation of Light in Textured Geometry (no backing)

Light In

Silicon

Texturing

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Propagation of Light in Textured Geometry + Metal Grating

Light In

Silicon

Texturing

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Calculated Absorption Spectrum for 2 mm mc-Si

Aluminum: 12.08% efficiency

3D PhC: 16.32% efficiency

DBR + 2D grating: 14.97% efficiency

P. Bermel et al., Opt. Express 15, 16986 (2007)3/31/2017 18ECE 695, Prof. Bermel

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Efficiency Enhancement of Period Structures

For optimized parameters, 2D grating efficiency enhance-

ment ranges from 7% at 128 mm up to 35% at 2 mm

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Thin c-Si Solar Cell Designs Incorporating Plasmonics

EM monitor

scattered light

diffractedlight

transmitted light (parasitic)

SPP (parasitic)

Active Si material

Air

Flat Ag back reflector

ZnO Ag NPTextured Ag back reflector

Active Si material

Air

EM monitor

scattered light

diffractedlight

transmitted light (parasitic)

SPP (parasitic)

EM monitor

scattered light

diffractedlight

transmitted light (parasitic)

SPP (parasitic)

Random texturing on the front and back surfaces, deposited conformally

Periodic (grating-like) texturing on the front and back surfaces, deposited conformally

Random texturing on the front surface combined with a back plasmonicnanoparticle

Plasmonics can double path length from ideal light trappingK. Catchpole & A. Polman, Appl. Phys. Lett. 2008, 93, 191113.

ECE 695, Prof. Bermel4/14/2015

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Simulation Methodology

t = t + ∆𝒕

Update E, D, H field

over volume

Start

t > t_max EndYesNo

t = 0

Calculate 𝑼𝒍𝒐𝒔𝒔 over

frequency over

volume

𝑶(𝑵𝟑)

𝑶(𝑵𝟒)

t = t + ∆𝒕

Update E, D, H field

over volume

Start

t > t_max EndYesNo

t = 0

Calculate 𝑼𝒍𝒐𝒔𝒔 over

frequency over

surface

𝑶(𝑵𝟑)

𝑶(𝑵𝟑)

> ≈

Volume-Integrated Finite-Difference Time Domain Method

Flexible Flux Plane Finite-Difference Time Domain Method

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

ECE 695, Prof. Bermel4/14/2015

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Simulation Methodology

𝒏𝒂,𝟏,𝟏

x y

z

Yee’s

unit cell

𝒏𝒃,𝟏,𝟏

𝑺𝒂,𝟏,𝟏

𝑺𝒃,𝟏,𝟏

Flexible flux planes offer rapid frequency-sensitive integration of parasitic losses.

ECE 695, Prof. Bermel4/14/2015

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Periodically Textured Cells: Theory and Experiment

200nm𝜆 = 800nm

ZnOp/c-Si

i/c-Si

Ag

𝐥𝐨𝐠𝟏𝟎 𝑬𝟐

𝟎

𝟏

𝟐

𝟑

𝟒

𝟓

𝟔

𝟕

𝟖

Detailed comparison of experimental and simulated total absorption, and the parasitic

component

Electric field energy distribution, with enhancement observed near the Ag/ZnO

interface

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

ECE 695, Prof. Bermel4/14/2015

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150nm𝜆 = 800nm

ZnOp/c-Si

i/c-Si

Ag

𝐥𝐨𝐠𝟏𝟎 𝑬𝟐

𝟎

𝟏

𝟐

𝟑

𝟒

𝟓

𝟔

𝟕

𝟖

Randomly Textured Cells: Theory and Experiment

Comparison of experimental and simulated total absorption, and the parasitic

component

Electric field energy distribution, with enhancement observed near the Ag/ZnO

and c-Si/ZnO interfaces

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

ECE 695, Prof. Bermel4/14/2015

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150nm𝜆 = 800nm

ZnO

p/c-Si

i/c-Si

Ag

Ag NP

(b)

𝐥𝐨𝐠𝟏𝟎 𝑬𝟐

𝟎

𝟏

𝟐

𝟑

𝟒

𝟓

𝟔

𝟕

𝟖

Ag Nanoparticle Cells: Theory and Experiment

Comparison of experimental and simulated total absorption, and the parasitic

component

Electric field energy distribution, with enhancement observed throughout the

structure, except Ag

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

ECE 695, Prof. Bermel4/14/2015

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𝜆 = 1058 nm

Ag NP

150nm𝜆 = 1058 nm

150nm

65 %

10 %

Ag Nanoparticle Cell Absorption Enhancement

ECE 695, Prof. Bermel4/14/2015

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w/ NP, 65 % absorption w/o NP, 10 % absorption

𝜆 = 1058 nm

Ag NP

150nm 𝜆 = 1058 nm150nm

Ag Nanoparticle Cell Absorption Enhancement

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

ECE 695, Prof. Bermel4/14/2015

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Ag NP Cell Absorption

Enhancement

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Again, the Ag nanoparticle increases field power throughout most of the structure, except the Ag itself; removing NPs cancels out most of this effect

Haejun Chung, K.Y. Jung, and

Peter Bermel, “Understanding

light trapping in nano-textured

silicon thin-film solar cells by a

novel simulation approach” Opt.

Express (2015, submitted)

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Ag Nanoparticle Cell Absorption Enhancement

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

ECE 695, Prof. Bermel4/14/2015

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Optimizing Ag Nanoparticle Cell Absorption

Jsc = 36. 6 mA/cm2

Jrefl= 5.0 mA/cm2

Jsc = 26.1 mA/cm2

Max Jsc = 43.8 mA/cm2

Jpar=3.7 mA/cm2

Haejun Chung, K.Y. Jung,

and Peter Bermel,

“Understanding light

trapping in nano-textured

silicon thin-film solar cells

by a novel simulation

approach” Opt. Express

(2015, submitted)

Effective path length: 700x enhancement

ECE 695, Prof. Bermel4/14/2015

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4/14/2015 ECE 695, Prof. Bermel 31

Optimizing Ag NP Cell Front Texture

Optimal correlated random front surface texture

Completely random front surface texture

Haejun Chung, K.Y. Jung, and Peter Bermel, “Understanding light trapping in nano-textured

silicon thin-film solar cells by a novel simulation approach” Opt. Express (2015, submitted)

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Next Class

• Next time: we will continue finite-difference time domain techniques

• Suggested reference: S. Obayya’sbook, Chapter 5, Sections 4-6

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