Characterization of 19.9% Efficient C

This work was supported by the U.S. Department of Energy under No. DE-AC36-99GO10337 with the National Renewable Energy LThanks to: Craig L. Perkins, Bobby To, Device Performance Grou

Hasoon,Tim Gessert, and Ramesh Dhere of NREL.

Ingrid Repins, Miguel Contreras, Manuel Romero, 

Metzger, Jian Li, Steve Johnston, Brian Egaas, C

Scharf; National Renewable Energy Lab

Brian E. McCandless; Institute for Energy 

Rommel Noufi; Solopower

NREL/PR-520-43247Presented at the 33rd IEEE Photovoltaic Specialist Conference held May 11-16, 2008 in San Diego, California
• 19.9% CIGS devices with improved fill 

recombination•See Repins et al. Progress in Photovoltaics 16, 

Device Area 

(cm2)

Efficiency 

(%)

Voc

(mV)

Jsc

(mA/cm2) 

Ff 

(%)

R 

( -

C1068-2 0.450 18.8 678 35.2 78.7 0.S2051-A1 0.408 19.2 689 35.7 78.1 0.C1675-11 0.406 19.3 668 36.2 79.6 0.C1812-11 0.409 19.5 692 35.2 79.9 0.M2992-11 0.419 19.9 690 35.5 81.2 0.
• Processing change: terminate three-stage C

without Ga•Improved device performance demonstrated evaporators and by three different operators•Why does this processing change improve devic

43210

-20 0 20 40

Time (sec)

Gallium

Indium

Device 

Name 

Area 

(cm2) 

M2992-11#5 0.419 1

C2183-12#5 0.416 1C2219-21#7 0.417 1

M2992-11#4 0.419 1M2992-11#6 0.419 1

C2183-12#4 0.417 1C2200-22#1 0.420 1C2213-22#2 0.994 1
• Characterization:

- Scanning tunneling luminescence (Sand cathodoluminescence (CL) mappin- Transmission electron microscopy (- Time-resolved photoluminescence (T- Capacitance-voltage (CV)- Grazing incidence x-ray diffraction (

• Note which results are typical of high-efficCIGS, and which results are particular to (>19.5%) CIGS.
STL and CL mapping

eeeeeeee-eγ (I, λ, x, y) 1 μm

CL: electron beam excitation~ 1 μm penetration depth

STL: excitattop 50 nm o

Measure intensity and wavelength of luminesced p

of position
Example: CL intensity as a function of position

19.9% device 13.0% device

SEM

CL map

Rn

abtd
CL and STL comparison

0

102030405060708090

100

0.9

1 1.1 1.2 1.3

Photon Energy (eV)

CL, 19.9%

STL 19.5%

CL 19.5%

STL 19.9%
TEM: Atomic number (Z) contrast

Decreased indication of nanodomains is unique 

2 nm

19.5% 19.9
TRPL

Relatively long lifetime is consistent with high efficiency recombinationFactors other than recombination (charge separation, intenalgorithm) also influence apparent lifetime. See Metzger 2008

0.01.02.03.04.05.06.0

10.0 12.0 14.0 16.0 18.0 20.0

Efficiency (%)

τ (ns)
CV

Zero-bias depletion width less than 0.5 mm, doping den2 x 1016 cm-3, consistent with >19% devices.

Zero-bias 

depletion width

10

15

234567

10

16

2

Carrier + Defect Density (cm-3

)

0.35 0.40 0.45 0.50 0.55

Distance from Junction ( μm)
GIXRD

IEC - no Ga

grading

NREL -

reverse 

process 

termination

NREL -19.9%

Ω = 0.25°

~ 50 nm depth

•Compared •Narrow peof high effi•Record deshift•Not explaiwould be re•Instead, denear surfac
•Ga segregates preferentially to α-phase domains, Cu vacandomains (Stanbery et al.) Hypothesis: Denying Ga to surf

perfect formation of Cu-deficient β-phase and thus the burie

Summary Summary Consistent with 

η (>18%) devi

Modified process termination 

Low nonradiative loss at grain boundaries 9No red shift between CL and STL Decreased evidence of nanodomains in TEM Long lifetime (TRPL) 9High doping density / short depletion width (CV)

9

Larger shift of GIXRD peak to high angle 

•Shallow probes indicate a more perfect and Cu-poor forma

surface region.

•Techniques probing into the bulk are consistent with high e