Al/Al O /nano-PbS energy selective contact for filtering hot carriers in solar cells2 3

Vitali Emelianov, Igor Konovalov

Concept

E - Selective contact(nano - PbS)

E - Selective contact(nano - PbS)

Absorber(bulk PbS)

Ef1

Ef2 EC

EV

Hot carrier solar cell with junctionsnano/bulk

- Carrier selectivity by band offset nontransitivity

Application and properties of Nano/Bulk contact

Ec

Ev

n=1

n=2

n=2

n=1

mn

m<mh n

Possible other originsof selectivity:Different effective mass m:

AND!

Different density of states: => semiconductor-specific!Probability of tunneling ? Grows at smaller m?

2

2

22

2n

mLEE Cn

hp=-

2/3

2

2, ÷

ø

öçè

æ==

-

h

mkTNeNn C

kT

EcE

C

p

Band structure of PbS:

Cubic,band edges at L-point)

Electron and holemasses are aboutthe same and small...

=> Large size effect!

(Overhoff, Rössler, 1970)(I. Kang and F. W. Wise, 1997)

(Picture: Wikipedia)

m

kEE Cn

2

22h=-

PbS: Large DOS near point , BUT!Different splitting of the valleys from band edges!!!=> Large difference between the density of statesof electrons and holes.

S

Experiments· SMD of PbS QDs for Energy Selective Contacts:

Crystalline PbS absorber onAl substrates

We would like to thank Mrs. M Friedrich for REMstudy and Carl-Zeiss-Stiftung for financial support.

· CBD of nanocrystalline PbS absorber on Al:

Conclusion: PbS is perspective material for hotcarrier solar cells with nano/bulk junctions

400 450 500 550 600 650 700 750 800 850 9000

10

20

30

40

50

60

Wavelength, nm

010203

040506

1,6 1,8 2,0 2,2 2,4 2,6 2,8 3,0Energy, eV

Lock-In spectrometer

· Light transmission in nanocrystalline PbS:

ref. Lock-In-Amp. outdriver

chopper

REM images of PbS QDson Al substrates

four diping sequences in

(K [Pb(OH) ]•KOH +

C6

H15

N) and (H2S•H

2O)

2 4

15 min exposure at RT in

Pb(C COO)2 + NH4OH +

SC(NH2)2

H3