Nanostructured solar cell

Transcription

1 aostructured solar cell bulk heterojuctio hybrid/dssc/dsh/et 3D cell e - coductor h + coductor TiO dye or Ps h + coductor TiO orgaic hybrid solar cell: polymer/dye/tio iorgaic polymer/polymer: MDMO-PPV/PCEPV polymer/orgaic: MDMO-PPV/PCBM polymer/carbo aotubes dye-sesitized solar cell (DSSC) electrolyte/dye/tio Dye-sesitized heterojuctio (DSH): CuI/dye/TiO extremely thi absorber: CuI/CdTe/TiO CuIS /TiO

2 Example: CuSC/TiO DSH -Spray pyrolysis/spi coatig of TiO -Icorporatio of Ru-535 dye -CuSC solutio icorporated ito ad above film coductive SO glass -absorptio of light by dye -electro ijectio ito CB of TiO -dye regeeratio by capture of electro from VB of CuSC iterpeetratig etwork heterojuctio B. O Rega ad F. Lezma, J. Phys. Chem. B 108, 434 (004).

3 Example: TiO /PbS QDs P. Hoyer ad R. Koekamo, ppl. Phys. Lett. 66, 349 (1995).

4 aostructured Solar Cells h + coductor (electrolyte, polymer) frot cotact dye or aoparticles e - coductor (TiO ) back cotact

5 Bulk heterojuctio (I) 1 1 E vac E C Eg 1 E g E V ssume periodic structure Flatbad solar-cell model 1 E C E E E g g g 1 E V E g

6 Bulk heterojuctio (II) 1 Dw1 w //period w1 w q1, w1 x 0 x q, 0 x w //charge desity Poisso Eq: d x dx Boudary coditio: w 1 0 w 1 x0 x0

7 Bulk heterojuctio (III) w 1 w 1: : x q 1 q1 w1 x dx x xw1 1 1 x q q x 0 dx 0 x x0 w q q 0 0 w 0 w q w x x xw ad xw w 1 x0 0 xw 1

8 Bulk heterojuctio (IV) 1 potetial w 1 0 w x0, D, D... 1: V x x dx x dx xdx : w1 q1 1 q1 1 q1 x0 w1 1 1 x x 1 x x x w 0 w 1 x q 1 w1 w 1 w q x0 w x x x q w V x x dx xdx q w w x w 1 x0 0 xw

9 Flatbad solar-cell model (I) Voltage differece: w w1 q w q1 w1 q 1 w1 w VV V 1 1 Charge eutrality: w w 1 1 w1 D 1 1 w D 1 otice, if 1 : q V D If: w1w D, the q V 1 1 D //same as p/ homojuctio with wd 1 qd V

10 Flatbad solar-cell model (II) kt q The voltage variatio (bad bedig) is small.

11 Flatbad solar-cell model (III) 1 E vac E C E V w 1 0 w w w 1

12 Flatbad solar-cell model (IV) Costat quasi-fermi levels: F i1 F i E E kt E E kt Ei kt 1 i1e i1e e Ei1EFp kt Ei EFp kt Ei kt 1 i1e i1e e p EF EF p E E i E i1 i E E E i i i1 F i F i E E kt E E kt Ei kt ie ie e i F i F E E kt E E kt p e e e i i E p p i kt i i1 i cosh E kt h i i r E e i kt EF Ei xe kt E F e i E p y kt EF F e E xy z p kt z F Fp x y e E kt e qv kt 1 i1 x r p ry 1 i1 xr i p y r i

13 Flatbad solar-cell model (V) ssumig acceptor dopig oly i side 1, door dopig oly i side : p D p ssume full ioizatio: D D Require: 1 p11 D p ssume: w1 w Use: y z r r z x i1 i ir x i1r y D x z r z r x z i1 i D ir i1r

14 Flatbad Solar Cell Model (VI) Defie: i vi1 r r r i1 u i r x z w u v e x z x x z w D w uvsih uvcosh z uv Rcosh uv Rsih atah u v R uv uv uv u v cosh sih sih cosh sih w uv sih z w v u asih atah uv z v u 1 0 x ze 1 e 0

15 Flatbad Solar Cell Model (VII) w 1 asih uv z w e 1 exp asih uv z vu tah 0 v u e e l e e e e v v 1 v 0 u u u x v w z exp asih u uv z ll other quatities ca be determied oce x is foud.

16 Flatbad solar cell examples ssume: The: lso: otice: i1 1 i1 ad i r i r 1 1 so h i r ir r i1 i r ad r ui r ad vi1 r i1 r so r i v u i1 i lso: i1 i h uv uv i1 i1 i i i i1 1 r uv h r x i1 w z exp asih i h z

17 Flatbad solar cell examples: case 1 (o dopig) (I) D 0 w 0 asih 0 0 x v z u 1 e qv kt i i y z x e qv kt i i1 i1 x i1 qv kt 1 e r h qv kt i he x r qv kt 1 i1 he p r y p i y i qv kt e r h

18 Flatbad solar cell examples: case 1 (o dopig) (II) i1 h h i h h p 1 1 p 1 1 qv kt p1 p1 h e p qv kt e h qv kt 1 e h Charge desity: qv kt e, 0 qh w x x qv kt q h e, 0 x w

19 Flatbad solar cell examples: case (asymmetric dopig) (I) case II: doped ssume: D h Let's also assume the sih argumet is large: w uv z D qv kt h e 1 This implies small quasi-fermi-level splittig: V kt q l D h ssume: w 0 D w 1 sih1 e e uv z e 1 e 1 w uv z I this case: x z v u w uv z w u y z z u x w

20 ow: i1 r z u p1 w h qv kt e D D i1 w 1 ru i1 D h Flatbad solar cell examples: case (asymmetric dopig) (II) D p D i z u rw i qv kt e D i i wr u r D i r D D p 1 1 p1 D D 1 q, w x0 Charge desity: x q, 0 x w With small quasi-fermi level splittig, the charge desity is geerally equal to the dopig level i the more lightly doped side

21 Flatbad solar-cell model: p/ + (I) p + p/ + case D D E C qv E F Ei E Fp E V p-side: p x D i e E i kt i1 E 1 e i kt i E e i kt x D x E 1 D 1 1 e i kt i E e i kt i i -side: Ei kt i e D x p More lightly doped side determies charge desity 1 1 Quasi-fermi level slope is small. ioized acceptors o p-side free holes o + -side

22 Flatbad Solar-Cell Model: p/ + (cot'd) o-equilibrium: qv E E E E F -side F F F p-side p p Cosider photogeeratio: -side: p-side: g p g D D G p p p 1 g The hole quasi-fermi level is foud from photogeerated holes o the p-side p g EFEi kt D e i 1 F 1 e i p i E E kt The electro quasi-fermi level is foud from the door cocetratio o the -side pg D qv kt l E i i Voltage may be much larger tha the built-i potetial differece V otice that holes are the miority carrier o the p-side for the p/+ juctio

23 Flatbad Solar-Cell Model: p/ + (cot'd) Compare to bulk, p/ homojuctio: qv OC l Jphoto kt J 1 0 p/+ case: L D L p assume: J photo Jphoto qg wl Lp J w 0 0 qgl D Dp qi L Lp J 0 D D qi L 0 i i Jphoto GL J D g qv oc g kt l i Electro geeratio o the p-side domiates.

24 aostructured solar cell: equivalet circuit p-cotact Equivalet circuit: Diode characteristics arise from iterfacial recombiatio May small subcells coected i parallel Vertical charge percolatio/hoppig represeted by series resistors Charge separatio may ivolve excito dissociatio -cotact