Fabrication of Organic bulk Heterojunction Solar Cell

Professor: Dr.Joodaki

Presented by: Farzane SenobariFall 2016

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outline

I. Introduction II. Organic Polymer solar cells

• Junction type• Working principle• The layer stack

III. Fabrication methods• Spin coating• Spray coating• Fabrication steps• specification

IV. Discuss the article

Introduction

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Organic solar cells (OSCs) have attracted strong attention in recent years • Clean• Renewable• Flexibility• Thinness• Simple Manufacturing Process

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Introduction

Organic solar cell (OPV)1. Dye sensitized2. Polymer3. Liquid crystal

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outline

I. Introduction II. Organic Polymer solar cells

• Junction type• Working principle• The layer stack

III. Fabrication methods• Spin coating• Spray coating• Fabrication steps• specification

IV. Discuss the article

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Organic Polymer solar cellsJunction type

o Single layero Bilayero Bulk Heterojunctiono Graded Heterojunctiono Continues Heterojunction

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Organic Polymer solar cellsWorking principle

Heterojunctiono A heterojunction is the contact of two materials with different electrical properties. o The donor is more electron rich than the acceptor.

Organic Polymer solar cellsWorking Principle Light absorption (exciton formation)

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Organic Polymer solar cellsWorking PrincipleExciton diffusion

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Organic Polymer solar cellsWorking PrincipleCharge transfer

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Organic Polymer solar cellsWorking PrincipleCharge collection

Organic Polymer solar cellsThe layer stack

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Active layer• Absorbs light• Consist of : donor + acceptor Transport layers• based on materials which have the capability of

being able to primarily transfer either electrons or holes

• hole transport materials : (MoOx)• electron transport material: (LiF), (Ca) ,(ZnO) ,

(TiO)

Organic Polymer solar cellsThe layer stack

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Electrodes• Most common material: (ITO) due to a high optical transmission combined with a low

resistance (a transmission of >85% at <10 Ohm/sq)• PEDOT:PSS (allow conductivities of more than 500 Scm with a transmission of >80%)

easier fabrication on flexible substrates,better tolerance towards bending compared to an ITO electrodeSubstrates•Glass•plastics

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outline

I. Introduction II. Organic Polymer solar cells• Junction type• Working principle• The layer stack

III. Fabrication methods• Spin coating• Spray coating• Fabrication steps• specification

IV.Discuss the article

Fabrication MethodsSpin Coating

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• The deciding process parameters involved in spin coating are:

1. Solution viscosity2. Angular speed3. Spin Time

• Advantage: possibility of making very well defined film thicknesses• Disadvantage: difficulty with scaling to large area samples

Fabrication MethodsSpray Coating

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(Http://Www.Nanowerk.Com/Spotlight/Id17636.Jpg)

Fabrication MethodsSpray Coating

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Atomization process:

1. Surface tension viscosity

2. Fluid density3. Gas flow

properties4. Nozzle design

Quality of the coated layer

1. Wetting behavior2. Surface properties3. Working distance4. Coating speed5. Droplet sizes6. Amount of

sprayed layers.

The Surface roughness :spray ~tens of nanometers spin coated ~few nanometers.

Fabrication Methods

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and powder

Dilution with methanolDissolution with glaciel acetic acidMixing(25 ̊C,1h,air)

Glass slide substrate

rinsed in acetonedried in air

The solutions were deposited on glass substrates by spin coating

Drying (300 ̊C,5min) heat treatment(500 ̊C,5min)

Annealing (600 ̊C,1 hr, air) ITO Film

Fabrication Methods

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1. cleaned with detergent2. ultrasonicated in acetone and isopropyl alcohol

for 15 min3. dried in an oven at 120 °C4. UV–ozone was used to treat the ITO surface

for 10 min

Fabrication Methods

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PEDOT:PSS solution

irradiated with UV light(emission centered at 365 nm and power density of 300 µW )in a dark glove box for 15, 30, 45, or 60 min.

sprayed (by handheld airbrush ,0.1 Mpa, distance 30cm,20s)spin-coated(5000 rpm ,30 s)

Annealing (150 °C, hot plate ,10 min)

The thickness of the PEDOT:PSS film was well controlled in the range of 30–40 nm

Fabrication Methods

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mixing in chlorobenzene solutiondifferent blend ratios(1:1; 1:1.5, 1:2, 1:3, and 1:4 (w/w))

sprayed (0.1 Mpa, distance 20 cm, 30 s)

spin-coated(1500 rpm, 30 s)

Polymer and PC70BM

The thickness of active ~ 120 nm

Fabrication Methods

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The active surface area of the device was 0.12 cm2 .

samples

transferred into a vacuum chamber

deposit Al (100 nm, pressure 2.0 * 10-6 Torr.)

SpecificationSpin coating Spray coating

• Max Temperature: 150 ̊C • No need to clean room • Needs vacuum for AL dep• Thickness260nm• Weight: light weight• Material: no rare, not toxic • PCE=4.94%• Short life time• Can’t be used in R2R process • flexible

• Max Temperature: 150 ̊C • No need to clean room• Need vacuum for AL dep• Thickness260nm • Weight: light weight• Material: no rare, not toxic • PCE=4.94%• Short life time• Can be used in R2R process • flexible

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outline

I. Introduction II. Organic Polymer solar cells

• Junction type• Working principle• The layer stack

III. Fabrication methods• Spin coating• Spray coating• Fabrication steps• specification

IV. Discuss the article

Discuss the article

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• Open Circuit Voltage ()• Short Circuit Current ()• Fill Factor(FF)

• Power Conversion Energy(PCE)

Discuss the article

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• UV irradiated PEDOT:PSS films were qualitatively similar to annealed films• The UV-irradiated solvent-modified PEDOT:PSS films have a high dipole moment. The PEDOT:PSS segments

are evenly distributed throughout the entire thin film and this could effectively reduce light scattering• Enlargement of the PEDOT grains and the reduction in the density of pores

improvement of conductivity by increasing the number of conducting pathways for carriers.

Discuss the article

UV irradiation time

15 min 30 min 45 min 60 min

RMS roughness 1.33 nm 1.24 nm 1.20 nm 1.17 nm

Discuss the article

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• Low performance + Low life time need a solution! Nanoparticle

The size of metal nanoparticles is one of key factors to strong light trapping

Discuss the article

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0.5 ml PEDOT:PSS solution+ 0.1 mg ZnO powder (size of nanoparticles smaller than 100 nm)

LiF thin layer

deposited by thermal vacuum evaporation

ultrasonicated (2 hours and 30 minutes, room temperature)

spin-coating

Discuss the article

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Discuss the article

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life time decreased due to:• The diffusion of PCBM molecules between the P3HT chains leading to a low

crystalinity

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References[1] http://energy.dtu.dk/

[2] http://plasticphotovoltaics.org/lc/lc-solarcells.html /

[3] https://en.wikipedia.org/wiki/Organic_solar_cell

[4] http://depts.washington.edu/cmditr/modules/opv/index.html

[5] http://edu.nano.ir/paper/68

[6] V.Doojin,” Fabrication of organic bulk heterojunction solar cells by a spray deposition method for low-cost power generation”, Appl. Phys. Lett,vol.91,Aug,2007.

[7] E. Celik,U. Aybarc,” ITO films on glass substrate by sol–gel technique: synthesis, characterization and optical properties”, JSST,vol.50,pp.337-347,June,2009.

[8] P.Kumar,” Comparison of properties of polymer organic solar cells prepared using highly conductive modified PEDOT:PSS films by spin- and spray-coating methods”, JJAP, vol.53,no.1s, Dec,2013.

[9] A. Radu,” The Influence of LiF layer and ZnO nanoparticles adding on the performances of flexible photovoltaic cells based on polymer blends”, DIG J NANOMATER BIOS,Vol. 6,no.3, pp.1141-1148, Sep, 2011.