DSSC and TF Poly-Si Solar Cells

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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

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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

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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
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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
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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

Photolithography
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The Equipments and Technology (Continued)

• 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)

Spin Coater
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Spin Coating

• Main purpose to achieve an even surface

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Side View of an Uneven Surface
slide
Uneven
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Side View of an Even Surface
slide
Smooth
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Spin Coating Demonstration
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The Equipments and Technology (Continued)

• 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

Sputter
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The Equipments and Technology (Continued)

• 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

Protective Mask
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The Equipments and Technology (Continued)

• AFM scans out 3D image of targets 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

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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
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Mask Aligning
UV
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Some Measuring Equipments
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Some Measuring Equipments
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Finding the Optimal RPM and Time
0.2 mL HAc (hydrogen acetate) in 100 mL DI water
TiO2 1.350.05 g with 40 drops of acetic acid
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Table 1 70 Drops of Acetic Acid
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Table 2 80 Drops of Acetic Acid
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Surfactant
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Surfactant
Table 3 2 g TIO2 ? 60, 70, 80 drops ? Triton
X 100 (surfactant)
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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
• 90C, 30 s
• Exposure
• Plastic mask of our design
• Duration 4 s

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Fabrication of DSSC

• Upper Electrode (2)
• Reverse Bake
• 110C, 120 s
• Reverse, flood Exposure (without mask)
• 15 s
• Develop
• AZ 300 developer for about 30 s
• Hard Bake
• 100C, 60 s

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In order to make the photoresist
negative REVERSE BAKE AND REVERSE FLOOD
EXPOSURE
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Fabrication of DSSC

• Spacers
• Spin-coating
• PR Su8
• Step 1 500 RPM for 5 s
• Step 2 3000 RPM for 30 s
• Soft bake
• 90C, 30 s
• Exposure
• Plastic mask of our design
• Duration 15 s

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Fabrication of DSSC

• Spacers
• No reverse bake or reverse flood exposure
• Develop
• AZ 300 developer for about 30 s
• Hard Bake
• 100C, 60 s

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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
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DSSC

• How It Works and How to Test It

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Electron Transfer Process
injection
regeneration
recapture
hopping
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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
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Thin-Film Poly-Silicon
Induce crystal 5000 1hr
Anneal at 5000C for 1hr
Remove Al layer by wet etching
Amorphous Si
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Closeup

• A Detailed Look at Our Experiments

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Photoresist Remains
50x
100x
200x
600x
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TiO2
50x
100x
good contact
TIO2

electrode
200x
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LabVIEW Portion

• Measurements Results

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LabVIEW Portion
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LabVIEW Portion
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LabVIEW Portion
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LabVIEW Portion
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The END
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Thanks