TitleInterface recombination & emission applied to explain photosynthetic mechanisms for (e-, h+) charges’ separation

Marco Sacilottia,c, Denis Chaumontc, Claudia Brainer Motaa, Thiago Vasconcelosb, Frederico Dias Nunesb,

Marcelo Francisco Pompellid, Sergio Luiz Morelhaoe, Anderson S. L. Gomesa

a Department of Physics, Universidade Federal de Pernambuco, Recife, Brazil. b Departament of Eletronics and Systems, Universidade Federal de Pernambuco, Recife, Brazil.c Nanoform Group ICB & UFR Sc. Techn. FR 2604 – Université de Bourgogne, 9 avenue A. Savary, Dijon, France. d Plant Physiology Laboratory, Universidade Federal de Pernambuco, Department of Botany, CCB, Recife, Brazil. e Physics Department, Universidade de Sao Paulo - Cidade Universitaria Sao Paulo Brazil

World Journal of Nano Science and Engineeringhttp://www.scirp.org/journal/wjnse Paper ID: 4400054

Support Information: SI-1

Energy staggered interface: electrical charge separation mechanism.

1

Figure SI-1-1, representing the energy staggered interface: electrical charge separation mechanism. How does the energy band bending arrive at the energetic interface? The flow of charges from one material to the nearby material creates an electronic no-equilibrium on both materials, near the interface. This electronic non-equilibrium creates potential variation. It creates the necessary electric field to separate charges: e- from h+.

CB

VB

VB

CBMaterial A

Material B

interface

-

+

Energy band bending.

Electric field = - grad V

Force = E x charge

energy = V x charge

Note that quasi-Fermi level EFB should go up,

CB & VB go down for B.

EFB

Note that quasi-Fermi level EFA should go down,CB & VB go up for A.

EFA

2

BC

BV

BV

BC

Cathode

Material A A

node

Material

B

interfaceFigure SI-1-2, representing the energy staggered interface. It represents the charge separation mechanism in a picturial slow motion maner. Excitation of such an energetic structure with only 4 photons.

+

-

2hv

2hv

-

+

+

-

+

- - - - -

++++

-

+

hvi

---

+++

-

++ + +

----

+

-+

hvi

+

-

+

-

+

-

+

-

+

-

+

-hvi

Energy balance: 4 hv photons as excitation3 hvi photons emission at interface1 (e-, h+) separated ( 25% efficiency)

hvi is related to the spent energy to separate (e-, h+).Note: photosynthesis is about 5% final efficiency. 3

BC

BV

BV

BC

Cathode

Material A Anode

Material B

interface

hvi

Figure SI-1- 3, representing the energy staggered interface: charge separation mechanism applied to photosynthetic first step processes. Note the hudge electric field crossing the interface for the AlInAs/InP system (see text). For organic molecules, this electric field should be much higher since the excitonic attraction is much higher than for inorganic materials.

-

+

-

+ +

+

-

-

waterO2

CO2

+ H2O sucrose

Interface electric field crossing the interface

Eband-bending ≈105 V/cm

4

Why is the interface emission peak so large? See it in the nexts slides…

5

Figure SI-1-4, representing the interface physical parts linked to the interface emission peak. All the terms of the equation below should change with the excitation intensity. Mainly ∆Qe + ∆Qh should change more than the others terms. This explain why the interface PL & EL emission peaks’ are so large.

Note: no quantum mechanics selection rules, for e- & h+ recombination at the interface 6

interface

hvi

<-- electr

ons

holes -

->

= S + Qe + Qh - Ex

Qe

Qh

S

_ + Ex=interaction

Material A

Material B

h absorption is possible

Energy levels to be filled up with h+, upon

light excitation.

Quasi-triangular shape quantum

well for e-.

Figure SI-1-5, representing the interface physical parts linked to the interface recombination/emission peak. The interface recombination and emission depends on the e- & h+ wavefunctions’ interface overlap. The 1 to 2 nm wavefunction penetration is for the AlInAs/InP system (see text).

No quantum mechanics selection rules for recombination;

because e- & h+ are seated on different materials. 7

interface

hv

<-- electr

ons

holes -

->

emission & absorption

Material A

Material B

Permanent e-population inversion

(µe- > µh+)

+~1 nm

- ~ 2 nm

Is there any meaning to talk about lifetime measurements

for all these hazardous energy levels (e-, h+) recombination?

S

h+ wavefunction

e- wavefunction