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 The etching of the FTO glass

To achieve the necessary voltage, a series circuit must be created inside the cell. To realize this objective, the FTO glass needs to be etched to establish a vertically conductive series circuit. This picture illustrates the cross-section of the structure and the positioning of 12 batteries on two glass electrodes. Follow the steps below:

1. Add 26.3 mL of 38% hydrochloric acid solution to a beaker and then dilute it with water to reach a total volume of 100 mL, creating a 2M HCl solution.
2. Apply Kapton tape to the FTO glass substrate to protect the areas that should not be etched.
3. Coat the FTO glass substrate with a layer of zinc powder.
4. Pour the 2M HCl solution over the zinc-coated FTO glass substrate and allow the reaction to complete.
5. Using a cotton swab, vigorously wipe the etched area on the substrate and rinse it with deionized water.
6. Finally, use a multimeter to check the resistance of the etched area, ensuring that the 12 conductive strips are 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 the photo-electrode

1. Attach Kapton tape to the glass to create the mask initially. Next, apply the TiO2 blocking layer using BL-1 paste with a glass coater. Subsequently, place the photo-electrode in an electric kiln, ramping up to 125ºC at a rate of 8ºC per minute without removing the Kapton masks. Maintain this temperature for 30 minutes, and then allow it to cool naturally to room temperature.
2. Coat the TiO2 porous layer with 18NR-T paste using a glass coater, then fire it with a ramp rate of 8 ºC per minute to 450ºC. Keep it at 450ºC for 30 minutes before allowing it to cool down naturally to room temperature.

Titanium dioxide sintering temperature curve reference

1.3 The preparation and sintering of the platinum electrode

PT-1 platinum paste is applied to the FTO glass using a glass coater. Subsequently, the coated glass is fired with a ramp rate of 8 ºC per minute, reaching a temperature of 500 ºC, and is maintained at this temperature for 30 minutes. The glass is then allowed to cool down to room temperature naturally.

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 in a light-proof glass bottle or beaker placed in a dark environment. Utilize a heat stirrer to consistently stir it at 50ºC for 18 hours to obtain the final N719 dye solution.
2. Immerse the prepared photo-electrode with the sintered porous TiO2 layer in the N719 dye solution in a shallow container for 24 hours at room temperature. Subsequently, carefully remove it and rinse off any excess dye solution on the dyed electrode using ethanol. Recycle the dye solution in the container by transferring it into a light-proof bottle.

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

To create the mask for the silver line, apply Kapton tape onto the glass. Utilize Acheson's 725A silver paste, which has been coated using a glass coater. Following the coating process, position the counter electrode in an electric kiln and bake at 120ºC for 15 minutes. Subsequently, allow it to cool down to room temperature naturally.

Silver wire mask making

Silver wire made of 725A silver paste

1.6 Electrolyte preparation

In this experiment, the Greatcell Solar EL-UHSE product was utilized. For the DIY version, two formulas can be followed:

1. 64mg of iodine (I2), 830mg of potassium iodide (KI), and 10ml of ethylene glycol.
2. 127mg of iodine crystals, 830mg of potassium iodide (KI), and 10ml of ethylene glycol.

1.7 Cell Assembling

The coated sides of the two electrodes are positioned facing each other and secured with several clips. Electrolyte is then injected between them using a dropper, and a few drops of EL-UHSE electrolyte, sourced from Greatcell Solar, are carefully added through 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.