1. DSSC and TF Poly-Si Solar Cells Dye-sensitized TiO 2 and thin film poly- silicon solar cells: fabrication and measurements of photon-to-electron conversion efficiencies using LabView

2. 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

3. 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

4. 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

5.  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

6.  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

7. Spin Coating Main purpose: to achieve an even surface

8. Side View of an Uneven Surface slide

9. Side View of an Even Surface slide

10. Spin Coating Demonstration

36.  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

37.  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

38.  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)

39. 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

40. Mask Aligning

41. Some Measuring Equipments

43. 0.2 mL HAc (hydrogen acetate) in 100 mL DI water TiO 2 : 1.35±0.05 g with 40 drops of acetic acid 30 20Time (second) 110012001300500RPM 4321 Finding the Optimal RPM and Time

44. Table 1: 70 Drops of Acetic Acid 3011007H 3011007G Less drops, not as evenly distributed3011007F Less TiO2 at the corners compared to D309007E not drops, painted on (corners)309007D 3010007C More drops at corners3011007B 3011007A CommentTime (second)RPM

45. Table 2: 80 Drops of Acetic Acid 407008E 108008D 207008C Not evenly spread309008B 3010008A CommentTime (second)RPM

46. Surfactant Triton X 100

47. Table 3: 2 g TIO2  {60, 70, 80} drops  Triton X 100 (surfactant) 307008VC 308007XC 309007XB 3012006XB Thicker than 7A, more bubbles3011006XA Good, with little bubbles309007XA CommentTime (second)RPMSurfactant

48. 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

49. 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

50. In order to make the photoresist negative: REVERSE BAKE AND REVERSE FLOOD EXPOSURE

51. 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

52. 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

53. 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

54. DSSC How It Works and How to Test It

55. injection regeneration recapture hopping Electron Transfer Process

56. 1. conducting F-doped SnO2-coated glass 2. compact TiO2 layer 3. dye-sensitized heterojunction 4. gold electrode Avoids direct contact between the HTM layer and the SnO2, which would cause short circuit Studying Photovoltaic Performance

57. Thin-Film Poly-Silicon Glass Bottom electrode ITO 300nm Induced metal layer Al 250nm Amorphous Si a-Si 250nm Induce crystal: 500 0 1hr Alpoly-Si 250nm Remove Al layer by wet etching Amorphous Si a-Si 4750nm Anneal at 500 0 C for 1hr poly-Si 5000nm

58. Closeup A Detailed Look at Our Experiments

59. Photoresist Remains 50x100x 200x600x

60. TiO 2 50x100x 200x TIO 2 electrode ] good contact

61. LabVIEW Portion Measurements & Results

62. LabVIEW Portion

66. The END