CHAPARALA, Prasad Mobile SOLAR  Alta Devices SLAC Mar 25 2013

Vice Pres of Product Development and head of tech development;
was formerly headof process reliability at Natl Semi...

v high efficient  GaAs  PVs...

Alta Devices  is his company...

High Efficiency Solar Cells for Mobile Power Applications

slac colloq  Mar 25 2013  at 4:15P...

founded in Jan 2008 by two renowned profs

Prof Harry Atwater  CalTech and
Prof  Eli Yablonovitch  UC Berk

filed 75 patents

2 facilities
rand Din Santa Clara
pilot line and HQ in Sunnyavle...

KPCB  did series A  and AugustCapital

strong investor syndicate  100M+  VC funded

series B:   6 companies
series C  6 more...

Solar TEchs:

you know abt rigid panels  effic 12 to 20%
Si/ CdTe/ CIGS

big glass panel  <  $1 per watt...  this is  98% of the industry...

can get  70 cents  per watt... panels...

then  another space:
flexible panels,
effic  only 4 to 10%
light weight
less than  $2 per watt

then there are  rigid panels for satellites (another, v expensive space)
>  $200 per watt
effic  30 to 33%
GaAs  is the very best!  most effic  but v expensive...

but IDEALLY  want...
flexible panels
effic 30%
GaAs
and less than $1 per watt

that is US!!! at Alta Devices...  our biz plan!

high efficiency,  flexible  GaAs  solar cells at low cost

high packing density  (wire-free interconnect;
high conversion effic
thin film
flexible form factor...

start with GaAs wafer  then put  MOCVD   solar cell on top

then  PEAL OFF the  solar cell layer  (this is  EPITAXIAL LIFTOFF)

front metal AR coating cut and test...

epitaxial liftoff... studied since 1987  but  Alta Devices... first to commercialize...

after pealing off the GaAs from the  substrate block  then you can  KEEP USING the
substrate AGAIN!!!

MOCVD  = metal oxide  chemovapor depos  layer...

***

core of the company is the

ELO  Epitaxial Lift-Off

what is ELO:

nondestructive separ of epitaxial thin films from substrates...

Why do ELO//

remove the cost of substrate
minimize material use
acces to the back surface of the cell

how to do it???
polymer above it..
metal above that
solar film above that
substrate on bottom

metal film provides mech support
HF  = hydrofluoric acid...  to etch...

metal :  what metals will work?

use a back metal reflector for enhanced photon recycling...

record single junction efficiencies:

29%  for a single cell (close to theoretical limit)

and for entire module  get  24.1%

high performance roadmap

today at 29%  next gen dual junc  at 33%  just started...
want to get to 37%

we hit a new dual junciton world-record  at  30.8%

that was with a GaInA/GaAs  tandem cell.. (that's gallium Indium Arsenide)

***
manufact:

start with GaAs  wafer

first a v thin layer of  AIA  Alumin Arsenid... will get lifted off...
then grow a 1 micron  layer  GaAs...
then deposit a layer of  back metal

then cover with layer of PET  (polyethylene sheet)

then etch away the release layer...

then  wafer is REUSED  and now have  plastic  carrier film with solar cell on it...

do it again by sliding the  sheet along... then cut it into sheets...

he passes around a  4 inch by 4 inch sheet of flex  solar cells...

pilot has started ramping...

next factory size will be 10 MW...(per year)

must come with tools that can grow films really fast!
typical can do 1 micron growth per day
want hundreds of microns per day...

back metal layer is applied by sputtering...

ELO Suite.. life-off  works...

a lot is borrowed from semicond industry...

can put these flex panels into  ROLLS and wire into series  ...

next factory size will be  10  Megawatts  Annual production)
(that is a v small by indust standards)
but signif less risk for investors...

highly flexible  <15 cm  radius of curvature.

high energy density  240 watts per  sq meter !
ultra light weight  1 gm/ watt

can be made into any form factor...

APPS:  UAVs,  automotive,, remote power,
consumer devices...

how to get to market...

first will be  UAV/ aerospace and military
focus on ones where no other choice...

then consumer electronics  (like cell phones...

UAVs  extended endurance...

remote locations to soldiers...

next is phones  and tablets  next
car;  rooftop on car...

finally   rooftop on house...  then utility...

now  products in UAV  and aerospace...

his primary job is reliability... can get  25 year lifetime!
beats  alll existing requirements...

will do rad hardening...
Q  vibration:  he  says... can be  made vibration hard...
robust interconnects...

consumer electronic  must be  about  $2 per watt
 (but some customers  will pay  $50 to $100 per watt...

aud Q:  mentions competing process:

PUMA  UAV

he shows a  hand held  UAV  abt 8 foot wingspan  (in backpack)

usually only flies for 2 hours...with its standard LiOn battery;  but can do

cells integrated into wing fabrication and get

130  watts of Alta cells on 8.5 foot wing span...!!!!
integrate right into  wing !!!!  laminate it right on!!!

now could get  6.5 hours endurance  from a 2 hour standard battery!!!
first demo flight  on Nov 6 2012

power hungry electronics on UAVs... communication...

they crash land:   fewer crashes means longer endurance

SKATE UAV...

from Aurora Flight Sci..
usually only < 90 mins of endurance  but
can incr to > 6 hours with alta cells
65 watts of solar!

its working, he shows it...

UAV market is huge!

next market is  charging mat...

10 watts from a 4 oz mat...  piece of paper

also for campers/ explorers/ miners/

can get 60 watts  from  24 oz  device!!!!

do iPAD while camping...

he shows a 20 watt mat and passes it around !  looking for a price of  $50 per watt...

govt buys  currently at  15 to 20 dollars per watt and we are  3X effcieint...

he passes around a 20 watt mat...

perhaps they can get to 10 dollars per watt...

from REI now can buy a 7 watt mat for  $100 bucks.... low efficiency...

tablet cover for iPAD... 10 watts  right on iPAD... he shows it.

charges at same rate as wall charger...

they can put  1.1  watt on a Samsung galaxy phone!!
  he has a working product!!!! in his pocket...

for samsung  galaxy  S3...  integrated  cover...

these are single junction...

perhaps in 2 years get to  dual junction  at 30% effic.

Automotive Apps..

typical mid size car  has 1 sq meter... on roof;

alta cells  225 to 250 watts... on a rooftop

CIGS cells  only 70 to 80  watts...

looking to have this in 2 to 3 years time...

BIPV  Vertical  Dow Shingle..  house/ commercial rooftop...

want 200 watts per sq meter roof top...

conventiona lpanels are  v v sensitive  to  high temps  eg  only 30 degr C  will cause decr effic
but NOT in GaAs... 5X as good...  (we lose less)

75 people in company and  77 patents...