Manufacturing large dye sensitized solar cell glass at home laboratory

Introduction

Dye sensitized solar cells are an easy-to-manufacture and cheap photovoltaic device that can be made in a home studio. However, the efficiency is still low, making it difficult to achieve commercial purposes (mainly it's limited by the conductivity of the FTO or ITO layer in its system). The pattern and color of the TiO2 layer and the etched matrix on FTO glass in DSSC can be highly customized, so it opens the possibility to smart surface design with aesthetic. The chemicals used in the experiment are mostly purchased from Greatcells Solar, therefore the manufacturing process is mostly conventional. The challenging parts here are temperature control to prevent glass deformation with large glass and the assembling techniques to prevent the electrolyte leaking and the corrosion of the silver traces in the cell caused by the iodine based electrolyte.

The history of the development of the 3rd generation solar cells.

DSSC schematic of the cells in this experiment in size of 30x60 cm.

Schematic representation of a TiO2-based DSSC. DSSC, Dye-sensitized solar cell.

1. Experiment

1.1 Conductive etching

1. In order to obtain enough voltage, we must make a series circuit inside the battery. To achieve this goal, we must first etch the FTO glass to make a vertically conductive series circuit. The cross section of the structure and 12 batteries are explained in Figure 1. Size and position in two glass electrodes. Add 26.3 mL of 38% hydrochloric acid solution to the beaker, and then add water to fill up to 100 mL to prepare a 2M HCl solution. Stick Kapton tape on the FTO glass substrate to protect the parts that do not want to be etched, coat a layer of zinc powder on the FTO glass substrate, and then cover it with 2M HCl solution, and wait for the reaction to complete. Using a cotton swab, vigorously wipe the etched area on the substrate and rinse with deionized water. Finally use a multimeter to check the resistance of the etched area, make sure the 12 conductive strips are all isolated from each other.

Photoresist wet film cured on FTO glass using 365nm UV lamp

After the photoresist wet film is fully cured, remove the Kapton tape to prepare for etching

Use a cotton swab to apply zinc powder to areas that do not have wet film photoresist

Mix diluted hydrochloric acid with zinc powder

Wait 15 minutes for the etch reaction to complete

Immerse the etched FTO in sodium hydroxide solution

After the wet film is completely peeled off, take out the FTO glass and clean the surface with water and ethanol

Make sure the 12 conductive strips are completely disconnected

Photoelectrode and counter electrode after etching

Apply Kapton tape mask on the etched FTO glass, ready to coat titanium dioxide and platinum paste

1.2 Preparation and Sintering of TiO2 Layer for Photoelectrode

1. Tape to the glass with Kapton tape and apply the TiO2 group barrier BL-1 slurry on a 60 x 30 cm piece of FTO glass using a glass rod applicator. Then, the FTO was sent into the electric kiln to reach 125ºC at a ramp rate of 8ºC per minute, and kept baking for 30 minutes and then naturally cooled to room temperature.
2. Coat TiO2 porous layer 18NR-T slurry in the same way, with a ramp rate of 8 ºC per minute to 500ºC.

Titanium dioxide sintering temperature curve reference

1.3 Counter electrode platinum layer preparation and sintering

1. Preparation of the counter electrode: PT-1 platinum slurry was also coated on the FTO glass using a glass coater, and then cooled to room temperature naturally after a ramp rate of 8 ºC per minute to 500 ºC and maintained for 30 minutes.

Platinum sintering temperature curve reference

Photoelectrode and counter electrode before entering the kiln for sintering

Photoelectrodes and counter electrodes are alternately placed in the kiln for sintering

TiO2 photoelectrode after sintering and before dyeing

1.4 Dye preparation

1. Dissolve 0.1 g of N719 dye powder in 250 ml of 95% ethanol, use a heating mixer to heat at 50ºC for 18 hours to obtain N719 dye solution, fill it into a light-proof glass bottle and place it in a dark place at room temperature.
2. Immerse the prepared photoanode in the N719 dye solution for 24 hours at room temperature, then take it out, recover the dye solution into a light-proof bottle, and then wash off the excess dye solution on the glass with ethanol.

Measure 100mg of N719 dye powder with a micro scale

N719 powder should avoid light pollution during heat stirring process

1.5 Preparation of silver wires on the counter electrode

1. Use Kapton tape on the glass to make the mask of the silver line. The silver paste model is Acheson's 725A, which is coated with a glass coater. After coating, place the counter electrode in an electric kiln and bake at 120ºC for 15 minutes, then cool down to room temperature naturally.

Silver wire mask making

Silver wire made of 725A silver paste

1.6 Electrolyte preparation

In this case the product from Greatcell solar EL-UHSE was used, or you can make your own electrolyte by following formula, there are two versions.
1. 64mg of iodine (i2), 830mg of potassium iodide (KI), 10ml of ethylene glycol.
2. 127mg of iodine crystals, 830mg of potassium iodide (KI), 10ml of ethylene glycol.

1.7 Cell Assembling

1. The coatings on the two electrode faces are facing each other, fixed with several clips and injected electrolyte between them, using a dropper to drop a few drops of EL-UHSE electrolyte purchased from Great Cell Solar from the open gap.

The prepared counter electrode (left) and photoelectrode (right

Assembled 30x60cm dye-sensitive battery (with printing pattern, no silver wire built-in vertical conduction series

Assembled 30x60cm dye-sensitive battery (no printing pattern, silver wire built-in vertical conduction in series

2. Results and obstacles

2.1 Measuring voltage

This experiment did not take the participation of the solar simulator but only with nature sunlight at noon. The open circuit voltage and open circuit current are measured as 5.8V and 51mA respectively.

Open-circuit current measurement at the 21st day from the manufacturing

Open-circuit voltage measurement at the 21st day from the manufacturing

2.3 Assembling without DuPont Surlyn film

The assembly of the FTO electrodes in this experiment was cost-effective and temporary, using only clips without Surlyn film. Consequently, some of the silver traces have corroded due to the iodine-based electrolyte. This corrosion occurred because it was challenging to heat-press the Surlyn film within the large-size glasses. The dissolution of the silver traces is evident in the pictures. However, despite this issue, the cell still exhibited an output of 0.33 watts under noon sunlight after one month, suggesting that there is no significant decline in performance. This may be attributed to the silver traces not being tightly bonded with the FTO, resulting in similar measurements between cells with compact and corroded silver traces. The proper method for assembling the electrodes with Surlyn film or other compounds at the DIY level is still an area that requires exploration and investigation.

After the silver paste interacts with the electrolyte, the silver paste melts and diffuses in the electrolyte

Reference

1. Martineau, David. n.d. “Dye Solar Cells for Real.”
2. Wei, Tzu‐Chien, Jo‐Lin Lan, Chi‐Chao Wan, Wen‐Chi Hsu, and Ya‐Huei Chang. 2013. “Fabrication of Grid Type Dye Sensitized Solar Modules with 7% Conversion Efficiency by Utilizing Commercially Available Materials.” Progress in Photovoltaics: Research and Applications 21 (8): 1625–33. https://doi.org/10.1002/pip.2252.
3. Mariani, Paolo, Antonio Agresti, Luigi Vesce, Sara Pescetelli, Alessandro Lorenzo Palma, Flavia Tomarchio, Panagiotis Karagiannidis, Andrea C. Ferrari, and Aldo Di Carlo. 2021. “Graphene-Based Interconnects for Stable Dye-Sensitized Solar Modules.” ACS Applied Energy Materials 4 (1): 98–110. https://doi.org/10.1021/acsaem.0c01960.
4. https://www.ossila.com/products/fto-glass-unpatterned#FTO-Glass-Etch
5. Make a Solar Cell - TiO2/Raspberry based. https://www.youtube.com/watch?v=WHTbw5jy6qU
6. “From Capitalist Realism to a Solarpunk Reality: Building the Infrastructures of a Better Future - YouTube.” n.d. Accessed February 9, 2024. https://www.youtube.com/watch?v=rsu8hHtomtQ.