Titanium Dioxide Self-ordered

Arrays for use in DSSC Photovoltaics

By: Anna DorfiJune-August

2012

Objectives:• Achieve TiO2 pore sizes of 100-150 nm• Use Scanning Electron Microscope for characterization (SEM)

• Length of 4-20 μm • 3-6 μm has been achieved, membrane stays on template and is

stable

• Increase surface area inside the nano-tubes.• “Bamboo” procedure of varying voltage

• Fill pores with P25 TiO2

• Use Ruthenium and test solar cell efficiency

Start:• Anodizations at 25C with .38 wt% NH4F and 1.8wt% H20 and

50 V. • 40-60 nm size pores, +4-5 nm

0 1000 2000 3000 4000 5000 6000 70000

2

4

6

8

10

12

14

Current vs. Time - AD008 (50V) Anodization 1

Time (every 2 s)

Curr

ent (

mA)

Developments• Higher Voltages• Bigger Pores

AD011 (70V)

Average pore size: 68.0 nm

AD009 (60V)

Average pore size: 49.0 nm

AD015 (80V):

Average pore size: 58.54 nm

AD017 (85V):

Average pore size: 81.34 nm

- Higher voltages seem to produce less of an ordered pore array

• Varying Voltage to create “bamboo” tubes with higher surface area.• Nanotube ridges

ridgesAD022 (75V 4min, 20V 2 min):

Average pore size: 79.92 nm

AD008 (50V 4 min, 10 V 2 min), 10 cycles:

Average pore size: 59.8 nm

ridges

0 200 400 600 800 1000 1200 1400 1600 1800 20000

5

10

15

20

25

30

35

40

Current vs. Time -AD018 (60V), 2nd Anodization

Time (every 2s)

Curr

ent (

mA)

Average pore size: 82.65 nm

ridges

AD018 (60 V 2min, 10V 4 min for 10 cycles @ 24°C):

• Higher NH4F wt% in anodization solution• Bigger Pores• Less ordered array

AD020 (75V and 20 V, .38wt% NH4F and 1.8wt% H20):

Average pore size: 66.68 nm

AD022 (75V and 20 V, .42wt% NH4F and 1.9wt% H20):

Average pore size: 79.92 nm

TiO2 Nanoparticle Filling

• The AD028 samples using the P25 had partially filled pores. The TiCl4 method will not be utilized in the future.

• Variations on the procedure using P25 powder will be used in the proceeding methods for filling.• 2 samples from AD049 will be put in the USB with the prepared

solution before being put in the autoclave.

• Older samples with 110 nm pores will be reproduced for future use.

Nanoparticle Procedures:• Each foil is put in a vacuum at 400C for 1.5-2 hours to become crystalline.

The sample is then cut in 4 pieces for use in different coating methods.

TiCl4 Method:• Two syringes of TiCl4 and some chloroform are put in a vacuumed flask with

the samples and stirred for 15 minutes.

P25 Method:• The solution of P25 particles was made with 100 ml of distilled water

and .015 M nanoparticle powder (calculated to be .12g P25 powder). • Using ultra-sonicating and magnetic force the solution was stirred for about

15 minutes at room temperature. The 30 ml of this solution is used for each sample.

• It is sealed and put in an autoclave at 85°C for 8 to 12 hours for coating. • The PCTs are finally achieves after the reactants are cooled freely and

washed with water, then heated at 400C for 2 hours.

AD028 – TiCl4 Method:

AD028_ TiCl4_1 AD028_ TiCl4_2

AD028 – P25 Powder Method:

AD028_ P25_1 AD028_ P25_2

AD028 P25 Sample 2:

Future Work• Vary the electrolyte solution used along with the voltages

and temperatures to get membranes with even bigger pores.• Continue to reproduce Samples AD028 and AD032 for

continued use in later steps

• Continue developing different procedures for filling the pores with P25 TiO2 nanoparticles.

• Dye the samples with Ruthenium dye and test their efficiency!

Thank you!!I would like to acknowledge Patrick Leidich and Prof. Dr, Tremel for their guidance and the DAAD RISE program for the research opportunity.