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Dye-sensitized TiO 2 and thin film poly-silicon solar cells: fabrication and measurements of photo n-to-electron conversion efficiencies using LabView. DSSC and TF Poly-Si Solar Cells. National Nano Device Laboratory Tainan Science Park. Taiwan Tech Trek (TTT) 2006 Interns: Eric Chang

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dssc and tf poly si solar cells

Dye-sensitized TiO2 and thin film poly-silicon solar cells: fabrication and measurements of photon-to-electron conversion efficiencies using LabView

DSSC and TF Poly-Si Solar Cells
national nano device laboratory tainan science park
National Nano Device Laboratory Tainan Science Park

Taiwan Tech Trek (TTT) 2006 Interns:

Eric Chang

Department of Electrical Engineering and Computer Sciences

University of California at Berkeley

Kevin Chen Ying Chang

Department of Electrical and Computer Engineering

University of California at San Diego

Yu-Kai (Kevin) Su

Department of Biomedical Engineering

Washington University in St. Louis

the clean room
The Clean Room

Different levels - NDL Tainan is level 10,000 per cubic feet

Requires standard uniforms

For our clean room, we have to have specialized hats, gloves, jackets, shoes, and mouth covers

Temperature, pressure, and humidity are constantly monitored so room condition can be kept at an optimal level

Standard Lab Clothing

the equipments and technology
The Equipments and Technology
  • Wet bench
    • Consists of four different chemical solutions to eliminate extra foreign particles
  • PECVD (Plasma Enhanced) - produces organic thin film by growing silicon dioxide/poly-silicon
  • Furnace is LPCVD (Low Pressure) – same function as PECVD requiring longer time for processing but better quality

Wet Bench

the equipments and technology continued
Photolithography

Includes following processes in order: priming, putting on photo resist (PR), pre-baking, UV exposure with mask, and then hard bake

Exposure - uses a mask to allow entrance of UV light to hit target wafer, which causes chemical reaction with the PR

Area uses yellow light so PR is not damaged

The Equipments and Technology (Continued)

Photolithography

the equipments and technology continued6
PR spin coated onto wafer (manually or automatically)

Track (automatic) –

Can perform all steps necessary for coating the wafer using an automated computer system

Spin Coater (manual)

Choose desired size of target

Manually test optimal parameters (RPM/time/position)

The Equipments and Technology (Continued)

Spin Coater

spin coating
Spin Coating

Main purpose: to achieve an even surface

the equipments and technology continued36
Thermal Evaporator and Sputter - both coat thin film of metal on the target wafer

Thermal evaporator – evaporated metal on bottom hits wafer on top, then molten metal gradually spreads evenly from center of wafer to coat surface

Sputter – molten metal on top rains down droplets at numerous positions to coat the wafer on the bottom

The Equipments and Technology (Continued)

Sputter

the equipments and technology continued37
The ICP and RIE are both machines that are used for etching

ICP is better since it can etch out the whole target wafer while the RIE cannot

Etchant is very corrosive and dangerous, so protective gear is required

The Equipments and Technology (Continued)

Protective Mask

the equipments and technology continued38
AFM – scans out 3D image of target’s surface

Nano-scale probe vibrates with a certain frequency at a synchronized distance away from the target

Vibration changes can be detected by a light that is reflected upon it, which gives data for image

Probe station

Uses microscope and nano-scale probe to make contact with different shapes of arrays on target

Probe station is utilized for contact with conductive materials, while AFM targets regular surfaces

The Equipments and Technology (Continued)
the mask
The Mask

The design and pattern of the mask - developed through AutoCad, then sent to specific company for production

Normal mask is created with glass and Chromium (1-2 months for completion)

Due to limited time, replaced the materials with plastic and chalk, (only an overnight process)

Masks

finding the optimal rpm and time
Finding the Optimal RPM and Time

1

2

3

4

RPM

500

1300

1200

1100

Time (second)

20

30

30

30

0.2 mL HAc (hydrogen acetate) in 100 mL DI water

TiO2: 1.35±0.05 g with 40 drops of acetic acid

slide44

RPM

Time (second)

Comment

7A

1100

30

7B

1100

30

More drops at corners

7C

1000

30

7D

900

30

not drops, painted on (corners)

7E

900

30

Less TiO2 at the corners compared to D

7F

1100

30

Less drops, not as evenly distributed

7G

1100

30

7H

1100

30

Table 1: 70 Drops of Acetic Acid

slide45

RPM

Time (second)

Comment

8A

1000

30

8B

900

30

Not evenly spread

8C

700

20

8D

800

10

8E

700

40

Table 2: 80 Drops of Acetic Acid

surfactant47

RPM

Time (second)

Comment

7XA

900

30

Good, with little bubbles

6XA

1100

30

Thicker than 7A, more bubbles

6XB

1200

30

7XB

900

30

7XC

800

30

8VC

700

30

Surfactant

Table 3:

2 g TIO2  {60, 70, 80} drops  Triton X 100 (surfactant)

fabrication of dssc
Fabrication of DSSC

Upper Electrode (1)

Spin-coating

PR: AZ 5214

Step 1: 500 RPM for 5 s

Step 2: 3000 RPM for 30 s

Soft bake

90°C, 30 s

Exposure

Plastic mask of our design

Duration: 4 s

fabrication of dssc49
Fabrication of DSSC

Upper Electrode (2)

Reverse Bake

110°C, 120 s

Reverse, flood Exposure (without mask)

15 s

Develop

AZ 300 developer for about 30 s

Hard Bake

100°C, 60 s

slide50

In order to make the photoresist negative:

REVERSE BAKE

AND

REVERSE FLOOD EXPOSURE

fabrication of dssc51
Fabrication of DSSC

Spacers

Spin-coating

PR: Su8

Step 1: 500 RPM for 5 s

Step 2: 3000 RPM for 30 s

Soft bake

90°C, 30 s

Exposure

Plastic mask of our design

Duration: 15 s

fabrication of dssc52
Fabrication of DSSC

Spacers

No reverse bake or reverse flood exposure

  • Develop
    • AZ 300 developer for about 30 s
  • Hard Bake
    • 100°C, 60 s
fabrication of dssc53
Fabrication of DSSC

Final steps to putting together our DSSC cell:

Put on electrolytes

Place the ITO glass carefully on top of the side with the electrolytes

Hold the ITO glass in place with something

electron transfer process
Electron Transfer Process

injection

regeneration

recapture

hopping

studying photovoltaic performance
Studying Photovoltaic Performance

3. dye-sensitized heterojunction

4. gold electrode

2. compact

TiO2 layer

1. conducting F-doped SnO2-coated glass

Avoids direct contact between the HTM layer and the SnO2, which would cause short circuit

thin film poly silicon

a-Si 4750nm

poly-Si 5000nm

Amorphous Si

Al

a-Si 250nm

Induced metal layer

Al 250nm

poly-Si 250nm

Bottom electrode

ITO 300nm

Glass

Thin-Film Poly-Silicon

Induce crystal: 5000 1hr

Anneal at 5000C for 1hr

Remove Al layer

by wet etching

Amorphous Si

photoresist remains
Photoresist Remains

50x

100x

200x

600x

tio 2
TiO2

50x

100x

good contact

TIO2

]

electrode

200x