Pras
ertS
inse
rmsu
ksak
ul,
Jaey
eong
Heo,
and
Roy
G. G
ordo
n
Depa
rtm
ent o
f Che
mist
ry a
nd C
hem
ical
Bio
logy
Harv
ard
Uni
vers
ity
Atom
ic L
ayer
Dep
ositi
on o
f Tin
(II) S
ulfid
e
2
Cu(In
,Ga)
(Se,
S)2
(CIG
S)Cd
TeHi
ghes
t ene
rgy
conv
ersio
n ef
ficie
ncy
of ~
20%
Adva
ntag
e�
Low
man
ufac
turin
g co
st�
Mod
erat
e ef
ficie
ncy
Lim
itatio
n�
Use
rare
ele
men
ts (I
n, Te
, and
Se)
�Co
ntai
n to
xic
elem
ent (
Cd)
NRE
L
wik
iped
ia
SnS
has s
ome
of th
ese
prop
ertie
s.
�Ba
sic C
riter
ia fo
r the
Abs
orbe
r Mat
eria
l.
�Su
itabl
e en
ergy
ban
dgap
( Eg
~ 1.
0-1.
5 eV
).
�Hi
gh o
ptic
al a
bsor
ptio
n co
effic
ient
( 10
4 -10
5 cm
-1).
�th
ickn
ess /
mas
s of m
ater
ial r
equi
red.
? Hi
gh q
uant
um y
ield
for t
he e
xcite
d ca
rrie
rs
? Lo
ng c
arrie
r diff
usio
n le
ngth
/ lo
w c
ombi
natio
n ve
loci
ty
�PV
effi
cien
cy
�Th
e co
nstit
uent
ele
men
ts a
re n
on-T
oxic
and
abu
ndan
t.
�no
n-ha
zard
, sca
labi
lity,
low
cos
t PV.
3
�Li
mita
tion
from
var
ious
dep
ositi
on te
chni
ques
�Co
ntai
n ot
her b
inar
y ph
ases
(SnS
2an
d Sn
2S3)
�Co
ntam
inat
ion
from
oxy
gen
(CBD
) and
chl
orin
e (C
VD)
�La
rge
devi
atio
n fr
om id
eal s
toic
hiom
etric
SnS
(tin
vac
anci
es)
�N
arro
w d
epos
ition
tem
pera
ture
win
dow
(25-
50 o C
rang
e @
~ 3
00 o C
)
4
Atom
ic L
ayer
Dep
ositi
on�
exce
llent
con
trol
ove
r sur
face
reac
tion
�w
ell-c
ontr
olle
d st
oich
iom
etry
�hi
gh d
ensit
y fil
m�
low
impu
rity
�lo
w d
epos
ition
tem
pera
ture
Sn(a
md)
2pr
ecur
sor
�ea
sily
synt
hesiz
ed�
suffi
cien
t vap
or p
ress
ure
�th
erm
ally
stab
le Sn(a
md)
2+
H 2S �
SnS
5
�M
inim
um e
xpos
ures
of 1
.5 To
rr·s
of S
n(am
d)2
and
1.1
Torr
·s o
f H 2S
are
requ
ired
to sa
tura
te th
e su
rfac
e re
actio
ns�
Grow
th ra
te o
f 0.9
0 Å/
cycl
e (1
20 o C
)
6
�N
ot d
etec
t oth
er b
inar
y ph
ase
(e.g
.Sn
S 2an
d Sn
2S3)
.�
Wid
e de
posit
ion
tem
pera
ture
win
dow
.
Ram
an S
pect
rosc
opy
7
S
Sn
SiO
2 su
bstr
ate
SnS 1±
0.01
Ruth
erfo
rd B
acks
catt
erin
g Sp
ectr
osco
py (R
BS)
�St
oich
iom
etric
SnS
(Low
Sn+2
vaca
ncy)
bel
ow 2
00 o C
�De
nsity
~ 4
.6 g
/cm
3(~
90%
of b
ulk
valu
e)
8
From
XPS
�N
o ca
rbon
, nitr
ogen
, or o
xyge
n de
tect
ed o
n Sn
Sfil
m d
epos
ited
belo
w 2
00 o C
.(SI
M)
�~
1-2%
car
bon
cont
amin
atio
n on
film
dep
osite
d ab
ove
250
o C.
Sn(a
md)
2st
arts
to
deco
mpo
se a
bove
250
o C.
SnS
CuI
nSe 2
GaA
s
CdT
e
Silic
on
a-Si
MD
MO
-PPV
(o
rgan
ic d
ye)
9
Eg ~
1.3
5 eV
�~
105
cm-1�
Nee
d ~
500
nm fo
r 95%
abs
orpt
ion
N
elso
n, J.
The
Phy
sics o
f Sol
ar C
ells;
Impe
rial C
olle
ge P
ress
10
Top
view
alo
ng b
axi
sSi
de v
iew
Ort
horh
ombi
c St
ruct
ure
( a�
b� c
and
�=
�=
�=
90o
)
a =
4.28
, b =
11.
20, c
= 3
.99
Å
(111)(040)
(101)
(002)
�De
sirab
le c
ryst
al o
rient
atio
n.�
high
er m
obili
ty th
roug
h th
e fil
m.
(Sin
gle
crys
tal:
μ /// μ
�~
10.)*
�ca
rrie
r tra
nspo
rt a
long
def
ect-
tole
rant
la
yer p
lane
crys
tal p
refe
rred
orie
ntat
ion
�do
uble
laye
r dist
orte
d N
aCl
stru
ctur
e.�
high
ly a
niso
trop
ic m
ater
ial.
c
b
http
://w
ebm
iner
al.c
om
*Nas
sary
, M.M
., Jo
urna
l of A
lloys
and
Com
poun
ds, 2
005.
398
(1-2
): p.
21-
25.
�Ha
ll m
easu
rem
ent
�la
tera
l res
istiv
ity �
~ 1
0 –
900
�•c
m
�lo
w h
ole
conc
entr
atio
n ~
1016
cm-3
�fe
w S
n+2va
canc
ies
�w
ide
depl
etio
n re
gion
in p
-n ju
nctio
n
�la
tera
l hol
e m
obili
ty ~
1-4
cm
2V-1
s-1
11
500n
m
SnS
Colu
mna
r str
uctu
re
�� ve
rtic
al/ �
late
ral ~
3�
low
er sc
atte
ring
from
gra
in b
ound
ary
�hi
gher
mob
ility
alo
ng c
ryst
al la
yer
plan
es
500n
m
Tsub
= 12
0 o C
Tsub
= 20
0 o C
12
Tim
e-Re
solv
ed P
hoto
lum
ines
cenc
e
�M
inor
ity c
arrie
r life
time
~ 90
ns
�Es
timat
ed m
inor
ity c
arrie
r diff
usio
n le
ngth
~ 1
.5 μ
m
�Sn
S is
a pr
omisi
ng a
bsor
ber m
ater
ial f
or e
arth
-abu
ndan
t, no
n-to
xic
thin
film
sola
r cel
ls.
�AL
D of
SnS
from
the
reac
tion
of ti
n(II)
am
idin
ate
and
H2S
.�
pure
SnS
phas
e ov
er w
ide
tem
pera
ture
rang
e.�
stoi
chio
met
ricSn
S�
no im
purit
y fr
om o
ther
ele
men
ts.
�lo
w d
epos
ition
tem
pera
ture
.
�O
ptic
al a
nd e
lect
rical
pro
pert
ies s
uita
ble
for t
hin
film
sola
r cel
ls.�
Eg =
1.3
5 eV
with
�>
105
cm-1
�[p
] ~ 1
016cm
-3w
ith μ
p~
1 -4
cm
2 V-1
s-1
�~
3x h
ighe
r mob
ility
thro
ugh
the
film
due
to c
olum
nar s
truc
ture
an
d cr
ysta
l orie
ntat
ion
�lo
ng m
inor
ity c
arrie
r life
time
(~ 9
0 ns
)13
Prof
. Roy
G. G
ordo
n
Prec
urso
r: Ad
am S
. Hoc
k an
d W
onta
eN
oh
Reac
tor:
Shen
gXu
and
Haris
h Bh
anda
ri
Colle
ague
s : Ja
eyeo
ngHe
o, L
eizh
iSun
, and
Hel
en P
ark
Hall
mea
sure
men
t: M
ark
Win
kler
, Ren
ee S
her,
and
Prof
. Eric
Maz
ur
14