Shigeru NikiDirector

Renewable Energy Research Center（RENRC）AIST

June 23, 2016

0

IW-CIGSTech7

OUTLINE

1

1. Introduction

2. NEDO CIGS Consortium

3. The Terawatt Workshop

4. Summary and Future Direction

2

Current Status of Energy-Related Issues in Japan

1. Self-sufficiency ratio in the primary energy supply dropped from

~20% in 2010 to ~6% in 2013.

2. CO2 emissions increased significantly (2013 was the worst ever).

After the Great East Japan Earthquake in March 2011,

Japanese Energy Policy for 2030

・Energy Security

・Economic Efficiency

・Environment with securing Safety

・energy self-sufficiency: 6%→24.3%@2030

・electricity cost: less than the current cost

・CO2 reduction target: 26% reduction from 2013

value @2030

Energy Mix for 2030 under Long-Term Energy Supply-Demand Outlook (Agency for Natural Resources and Energy: June 2015)

3E+S

Target

Renewable Energy: Maximum introduction with reduced costs

3

Current Status of PV industries in Japan

• Started R&D of PV technologies at 1974 under “Sunshine Project”

• Share of Japan’s module production dropped 50%@2005 →10%@2014 due to intensification of global price competition not

due to the level of technologies.

• Over intensification of global price competition lead to stagnation

and bankruptcy to many module manufactures as well as

introduction of anti-dumping tariff.

• Japan is leading PV technologies demonstrating world record

efficiencies of h=25.6% of silicon heterojunction cell (Panasonic)

and h=22.3% of CIGS cell (Solar Frontier), etc.

• Strong domestic value chain based on various technologies

• Emergence of the power conditioning system (PCS) manufactures

since the start of Japanese FIT in 2012 becoming the Japanese

strength.

4

• Started subsidy program for residential PV system in 1994

• Japanese FIT for PV started in July 2012

• 33GW already installed , 79GW of proposals approved by METI

• Unbalanced geographical distribution

• Unbalanced deployment of PV compared to other renewables

• Unlimited possibilities of curtailment in some regions

Deployment (FIT and Subsidy)

FIT started

6

300kW

500kW

Demonstrationsite

Main Building

Experiment Building

Smart SystemResearch Facility(3MW PCS testing)

Photovoltaics

Wind Power

Geothermal

Hydrogen Energy Carrier

Energy Network

Fukushima Renewable Energy Institute, AIST (FREA)

• International R&D base for renewable energy

10th regional research base of AIST

• New industry promotion in the area damaged by the disaster

Founded in April 2014

Missions (based on the government’s announcement, July 2011)

PV technologies at AIST

Hokkaido Center

Tohoku Center

Tsukuba Center &HQ

Tokyo HQ

Kyushu Center

Chugoku Center

Shikoku Center

Kansai Center

Chubu Center

FREA (from Apr. 2014)

c-Si technology, energy management

Long-term stability

Oudoor testing

RCPV HQ

・CIGS, TF-Si, Perovskite, Tandem

・Module reliability

・Calibration, measurement 7

Renewable Energy Research Center (RENRC) and Research Center for Photovoltaics (RCPV)

RENRC HQ

8

2. NEDO CIGS Consortium

2013 2015 2020 2025 2030

・Improvement in efficiencies and cost-down・Application of the technologies developed in the previous projects

Equivalent to commercial

electricity

Equivalent to general

power sources

・Novel materials and structures・Application of novel technologiesfor mass-production

0

Cost

[JPY/kWh]

System (example)・Module efficiency: 22%・Utilization factor: 14%・Operation period: 25 years

System (example)・Module efficiency: 25%・Utilization factor: 15%・Operation period: 30 years

14 JPY/kWh

7 JPY/kWh

NEDO PV Challenges

New Japanese PV roadmap announced in Oct. 2014.

Cost target: 14 JPY/kWh in 2020, 7 JPY/kWh in 2030

New NEDO PV projects started (2015-2019)

Mid term h target@2017: cell 22%, submodule 19%

Final h target@2019: cell 23%, submodule 20%

Solar Frontier (Dr. T. Kato)

AIST: Research Center for Photovoltaics (Dr. H. Shibata)

Tokyo Tech. (Dr. A. Yamada):

Ritsumeikan Univ. (Dr. T. Minemoto):

Kagoshima Univ. (Dr. N. Terada)

Ryukoku Univ. (Dr. T. Wada)

Tsukuba Univ. (Dr. K. Akimoto)

Tokyo Univ. of Sci. (Dr. M. Sugiyama)

CIGS Consortium Japan (Dr. S. Niki)

Solar Frontier AISTselenization

sulfurization 3-stage evaporation

Absorbers, Devices

CIGS Consortium Japan

Kagoshima Univ.

band profile

Ryukoko Univ.

material design

Tsukuba Univ.

defects

Tokyo Tech

buffer/absorber

Ritsumeikan Univ.

TCO/buffer

Tokyo Univ. Sci.

grain boundary

exchange

data & samples

Acceleration of R&D by effective collaboration

Cost 23JPY/kWh 14JPY/kWh 7JPY/kWh

Module price 61JPY/W 48JPY/W 31JPY/W

Module efficiency 14% 16% 20%

Cell efficiency 21% 23% 25%

Module cost （comparative） 1.0 0.87 0.71

Target schedule 2015 2020 2030

Cost Analysis of CIGS technology

Material parameter Current cells Ideal Cell

carrier recombination@CdS/CIS interface

Yes No

Bandgap （eV） 1.25 1.40

Electron lifetime（sec） 1×10-8 1×10-6

Hole lifetime（sec） 1×10-8 1×10-6

Electron mobility（cm2/Vs） 60 100

Hole mobility（cm2/Vs） 25 25

Hole concentration（cm-3） 2×1016 3×1017

Surface reflection loss 10 % 0 %

Device characteristics Current cell Ideal cell

efficiency（％） 20.1 26.2JSC（A/cm2） 33.5 31

VOC（V） 0.75 1.0FF 0.8 0.85

Device Simulation

High-performance CIGS solar cell/submodule research

22.8 (Cd-free)

22.7 (CdS)

22.3 (CdS; certified)

22.0 (Cd-free; certified)

18.9

18.6 (certified)

15.9

19.0

20.0

Cd-free

Submodule

Production

Module

Small-area Cell

20.9

(Cd-free; certified)WR cell eff.

SF submodule

NEDO target

40cm2 submodule

0.5cm2 small area cell

η=18.6%

glass substrate

Mo back electrode

Passivation and light confinement layer

CIGS absorber layer

back surface layer

front surface layer

buffer layer

TCO layerDevelopment of novel TCO materials

Improvement of hetero-junction

interface qualities

Improvement of crystal grain boundaries

Development of back surface passivation

technologies and light confinement

technologies

Development of super high-efficiency CIGS technology

Development of buffer layer

deposition technologies

Improvement of crystal qualities

AIST group

device fabrication, absorber supply, junction formation, etc.

Novel devices and processes for efficiencies of 23% and more

Interface Engineering forHigh-Performace Chalcogynide Thin-

Film Solar Cells

ObjectiveCu(InGa)Se2 thin-film solar cell consists of many interfaces, such as CdS/CIGS heterointerface, grain boundaries (GBs), and rear contacts. The efficiency of CIGS solar cells is dominated by these interfaces. In the research work, Tokyo Tech focuses on the interface engineering to improve the efficiency.

Themes CdS/CIGS interface and grain boundaries (GBs) Surface treatments Band profiling and back contact engineering

2016/6/23

Passivation technology by band alignment control

Research Object:Reduction of recombination at front junction and increase Voc & FF

1. Reduction of defect density at front junction

2. Carrier separation by band engineering

New TCO and buffer layers for band alignment control

Recent topic: (Cd,Zn)S/(Zn,Mg)O as more transparent buffers

0.0

0.2

0.4

0.6

0.8

1.0

400 600 800 1000 1200

Wavelength [nm]

EQ

E

x=0 [Eg of (Zn1-x

,Mgx)O: 3.3 eV]

h: 18.4% (JSC

: 38 mA/cm2)

x=0.21 [Eg of (Zn1-x

,Mgx)O: 3.73 eV]

h: 20% (JSC

: 39.3 mA/cm2)

Eg of (Cd,Zn)S: 2.7 eV

Designated area: 0.5 cm2

x=[Mg]/([Mg]+[Zn])

Varying

w.o. ARC

(SF)

Studies on various materials, interfaces and grain boundaries in CIS solar cells by a combination of theoretical calculation and experimental methods

Soda-lime glass(soda-lime glass)

Back contact (Mo)

Absorber

Cu(In,Ga)(S,Se)2

buffer layerCdS (Zn-O-S, In-S)

ZnO

ZnO:Al (ITO)

Au /NiCr

Materials design of Interface between CIGS

absorber layer and Mo back contact

•MoSe2 interface layer

Materials design of CIGS absorber layer

• Cu(In,Ga)(S,Se)2 absorber layer

• Cu(In,Ga)3(S,Se)5 surface layer

• Defects in CIGSS crystals

• Grain boundaries of polycrystalline CIGSS thin

films

Materials design of interface between buffer layer and

absorber layer

• Diffusion of various elements such as Cd or Zn atom

from buffer layer into CIGS absorber layer

• Electric structures of various Cd-free buffer layers

18

Ryukoku University

Band Offsets • c(Buffer)

Originated • OVC

• PDT

Band bending

@ CIS/Buffer

@ Buffer/TCO

VBM

CBM

MoTCO CIS

Buffer Modified Reg. by PDT

Determination of Band Profiles throughout the Cell-Structure (I);

for Developing Key Technologies for High Performance (Kagoshima Univ.)

Determination of Electronic Structure

by using Direct and Inverse Photoemission

(in-situ PES/IPES)

Band Offset (CBO, VBO) at CIS/Buffer

and Buffer/TCO Interfaces

Optimization; Suppression of Interface-Loss

Built-in Potential

(Sum of Interface-Induced Band Bending)

through the CIS/Buffer/TCO Structure

Clarification the Upper Limit of Voc

Clarification of

Impact of Post-Deposition-Treatment (PDT)

on Electronic structure of CIS

and Band Alignment at the Interface

Mechanism

of PDT

Band OffsetsVBM

CBM

MoTCO CIS

Buffer Modified Reg. by PDT

Subject ：Determination of Band Profiles through the Cell-Structure (II); (Kagoshima Univ.)

for Developing Key Technologies for High Performance

Determination of Band Profile

by using Cross Sectional

UHV-Kelvin Probe Microscope

(UHV-KFM)

Visualization of Band Profiles in CIS

(Gap-, Edge-Grading along Depth Direction)

Feedback to CIS-Fabrication (High Voc, Jsc)

Visualization of Band Profiles

at the CIS/Mo Interface

Enhancement of Back Surface Field

PDT

Band Gradient at

Back Contact

Band bending

Band Profile

in CIS

Characterization of Defects in CIGS and

Development of the Technique to Suppress the Defect Formation

Research Results Obtained to date

1. Defect level with 0.3eV from the valence band <Admittance measurements>

Result: Assigned as VCu-Vse; Not so sensitive to device performance

2. Defect level with 0.8eV from the valence band <Photo-capacitance measurements>

Result: Works as recombination center; Related to anti-site defect

3. Impurity phase in CIGS <Raman scattering spectroscopy measurements>

Result: Formation of Cu2Se; Affects significantly device performance

Research Plan1. Detection of defect level with 0.4eV ～ 0.7eV where nobody surveyed to date

Method: Photo-capacitance measurements with IR light source etc.

2. Identification of atomic structure of the 0.8eV-defect

Method: Positron annihilation, Pump probe EXAFS and so on

3. Development of the technology to suppress the Cu2Se formation

Method: Examination of deposition condition etc.

4. Identification of electronic properties at the interface, surface and grain boundary

Method: EBIC, Microscopic PL and PL decay etc.

University of Tsukuba

Poly-CIGS solar cell Epi-CIGS solar cell

Poly-CIGS

Poly-Buffer

ZnO-based TCO

Poly-Mo

SLG

Epi-CIGS

Epi-Buffer

ZnO-based TCO

Epi-Mo

Single crystal

Diffusion from

substrate

(Na,K,Ca,Mg,

etc.)

No diffusion

from substrate

Grain

boundary

Lattice defects

No GB

Low defects

Interface defects Low-interface defect

Band profile

Buffer layerInterface

defects

Carrier control

Impurity doping

Low-bulk defectBulk defect

Low・defects

Band offset

Epitaxial growth

IssuesIssues

Low defects

Epitaxial growth

Surface cleaning

BenefitsCell structure Cell structure

Exploring the pathway for high efficiency CIGS

solar cells by epitaxial growth technique

High mobility-TCO

Task: To provide the guideline for high-efficiency CIGS solar cells by using an

epitaxial growth technique leading to no grain-boundaries and less defects.

Tokyo University of Science

TUS

Epitaxial growth

High mobility-TCO

23

3. “The Terawatt Workshop”

Global Alliance of Solar Energy Research Institutes (GA-SERI)

March 17-18th, 2016 Freiburg, Germany

Worldwide gathering of 50 experts from Germany, Japan, the United

States and elsewhere to discuss the future of PV.

Representatives from research institutes, industry and funding and

financial organizations met in “Kaufhaus” in Freiburg, Germany

Discussions centered on the challenges that must be overcome to

transform the energy system and enable PV to supply a significant

portion of the world’s energy.

25

The Terawatt Workshop (3)“Statement (extracts)”

With annual global PV installations reaching 60 GW in 2015, approaching global production capacityIn view of drastically reduced PV costs, cumulative global installations in excess of

3 TW are anticipated by 2030, continuing current R&D and investment paths.To provide a major contribution to global climate goals, total installations on the

order of 20 TW will be needed by 2040. This will require continued investment in worldwide R&D to reduce production costs, increase efficiency and improve reliability.An increasingly flexible electricity grid, increased availability of low-cost energy

storage and demand side management will also play key roles in enabling accelerated PV deployment. In addition to providing a significant fraction of world electricity, PV has the

potential to provide low cost energy for mobility and heating market demands. Fh. G. ISE (Germany), AIST (Japan), and NREL(USA) are the member institutes of

GA-SERI. GA-SERI was founded in 2012.

Global gathering addresses PV role in energy prosperityand climate change mitigation and announces transition to a new stage that

will carry PV to the terawatt range

Press release from AIST, Fh.G and NREL on March 30, 2016

4. Summary and Future Direction1. CIGS technology climbed to the next level.

2. Over 20%-efficiency commercial modules can be expected in the near future.

3. Further improvement of small-area cell efficiency is wanted to show the potential of the CIGS technology.

4. Breakdown of high-efficiency potential to the production is critical to compete with other technologies. (Is this the roll of industry only? or can the research institutes help?)

5. Reliability issues have become more important. The allying of CIGS community is important for standardization.

(for example, IEC61215) 5DO 10.3 Sakurai et. al.,We need more companies to make sustainable CIGS industry.

CIGS technology is one of the core PV technologies which is sustainable

in the future. (competitive in terms of performance as well as cost

with respect to current Si and CdTe technologies.

Acknowledgments

CIGS Consortium:

Solar Frontier, Tokyo Tech, Ritsumeikan Univ.

Kagoshima Univ. Ryukoku Univ. Tsukuba Univ.

Tokyo Univ. Sci.

S. Ishizuka, H.Tampo, T. Koida, Y. Kamikawa, J. Nishinaga,

S. H. Choi, K. M. Kim, S. H. Kim, H. Shibata, A. Yamada,

H. Mizuno, R. Ohshima, K. Makita, T. Sugaya, K. Hara,

A. Masuda, K. Matsubara

AIST Research Center for Photovoltaics (RCPV):

This work is supported, in part, by New Energy and Industrial

Technology Development Organization (NEDO).

282016/6/23 Copyright © National Institute of Advanced Industrial Science and Technology (AIST). All rights reserved.

あらたうと青葉若葉の

日の光芭蕉

Thank you for your attention.

2016/6/23 29Copyright © National Institute of Advanced Industrial Science and Technology (AIST). All rights reserved.

Appendices

30

How to improve the energy self-sufficiency ratio in the primary energy supply?

Copyright © National Institute of Advanced Industrial Science and Technology (AIST). All rights reserved.

Trend in energy self-sufficiency

・FY2010:19.9%, FY2011:11.2%, FY2012:6.3%, FY2013:6.0%

Goals set to be 24.3% at FY2030

・Renewable Energy：13-14%, Nuclear：11-10%

石油３０％程度

ＬＰＧ３％程度

石炭２５％程度

天然ガス１８％程度

原子力１１～１０％…

再エネ１３～１４％…

２０３０年度

４８９百万ｋｌ程度

一次エネルギー供給Fundamental plan of action・Maximum cutdown of energy usage

・Maximum introduction of renewable energies

・Improve in efficiency for thermal power plant

Reduce the dependence on Nuclear

RE：maximum introduction

with suppressed cost

Renewable(13-14%)

Nuclear(11-10%)

LNG:18%

Coal:25%

Oil:30%

FY2030

Energy Mix for 2030 under Long-Term Energy Supply-Demand Outlook (Agency for Natural Resources and Energy: June 2015)

LPG:3%

31

Energy Mix (Electricity Outlook)ーmaximum introduction with suppressed costsー

Copyright © National Institute of Advanced Industrial Science and Technology (AIST). All rights reserved.

Role of RE will be expanded.・RE: 10.7%（2013） out of total electricity → 22-24%（2030）・RE except for hydro power: from 2.2% （2013） to 13-15%（2030）

太陽光 7.0%

程度

風力 1.7%程度

バイオマス3.7-4.6%程度

地熱 1.0-1.1%程度

太陽光 風力 バイオマス 地熱

石油・ＬＰＧ

6.6%

石油・ＬＰＧ

13.7% 石油 3%程度

石炭 25.0%

石炭 30.3%

石炭 26%程度

ＬＮＧ 29.3%

ＬＮＧ 43.2％

ＬＮＧ 27%程度

その他ガス 0.9%

その他ガス 1.2%

28.6%原子力 1.0%

原子力 22-20%程度

水力 8.5% 水力 8.5%

水力 8.8-9.2% 程度

再エネ（水力以外） 1.1%再エネ（水力以外） 2.2%

再エネ（水力以外）13-15%程度

２０１０年度 ２０１３年度 ２０３０年度

（総発電電力量）10,650億kWh程度

電源構成

石油 石炭 ＬＮＧ その他ガス 原子力 水力 再エネ

RE introduction targe

(incl. hydro)

22-24% (2030)

Energy Mix for 2030 under Long-Term Energy Supply-Demand Outlook (Agency for Natural Resources and Energy: June 2015)

Renewable

Nuclear

LNG

Coal

Oil

Hydro

Geothermal(1.0-1.1%)

Biomass(3.7-4.6%)

Wind(~1.7%)

PV (~7%)

32

“The integration of large shares of various renewable energy into the energy system will go

hand-in-hand with the need to increase the operational flexibility of power system.

“Electricity storage systems can be classified by size according to their input and output

power capacity and their discharge duration (hours).”

“Hydrogen-based technologies are best suited to large-scale electricity storage applications at

the megawatt scale, covering hourly to seasonal storage.”

Storage Technology -Various Storage Technologies-

33

・hydrogen carriers :materials that enable chemical energy storage through

reversible hydrogenation

・large scale storage at a high density (MCH（methylcyclohexane：6wt%-H2）、NH3

（ammonia：17wt%-H2）, etc.)

・Cost analysis: transportation of imported renewable energy by hydrogen carriers (Liq. H2

and MCH)

・Dr. Ishimoto indicated that ”In this paper, ....the re-electrification cost in Japan is reduced

to the range of the present electricity price in Japan.”

Storage Technology - Hydrogen energy carrier-