COMPOSITE FILM AS COUNTER ELECTRODE IN DSSC

• Main Author: Rahmawati S, Risa
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/52163
• Institution: Institut Teknologi Bandung

The development of technology is very fast, but it still cannot answer the world's energy demand. A dye-sensitized solar cell (DSSC) is an inexpensive and environmentally friendly technology that efficiently harvests solar energy. This research focused on the modification of counter electrodes and photoanodes on DSSC. The counter electrode acts as a cathode that reduces I - to I- catalytically. In contrast, the photoanode acts as an anode that functions to absorb photons and inject electrons to the external circuit. Platinum (Pt) is typically used as the counter electrodes in DSSC. Unfortunately, Pt is very expensive, and its availability is limited in Indonesia. Carbon-based material is an alternative material that can replace Pt as the counter electrode in DSSC. Carbon-based material has many advantages, including high corrosion resistance, good catalytic activity, good electrical conductivity, environmentally friendly, inexpensive, and abundant in the earth's crust. Among various carbon materials, graphene has many advantages that no other carbon material can provide. Graphene has high electron mobility, good electrical and thermal conductivity, nearly transparent, and has a large active surface area. However, graphene is poor on the electrocatalytic side. In this research, a compound similar to graphene has been synthesized, namely reduced graphene oxide (rGO). Various rGO-polymer composites have been developed to cover up the limitation of rGO since 2006, where the conductive polymers act as the rich electrocatalytic active side, while rGO as the high electrical conductive substrate. One conductive polymer with good characteristics is polyaniline (PANI). The pair of free electrons in the -NH-PANI is used together by aromatic carbons from graphene form covalent bonds, which help accelerate the charge transfer along the PANI chain. Good charge transfer in graphene/PANI composites enhances the DSSC performance by facilitating the rapid reduction reactions on counter electrodes. In this research, rGO was synthesized by the sonication-assisted oxidation method that followed by reduction. While PANI was synthesized using the rapid mixing method. Blend rGO/PANI composite is then applied as a film on top of the synthetic graphite substrate laminated glass by screen printing techniques. The rGO/PANI composite film was made in several weight compositions of 5:1; 4:1; 3:1; 1: 1; and 1:3 to obtain counter electrodes with optimum performance. DSSC cell fabrication in this dissertation uses photoanodes that made of J25 TiO2 film, Ruthenium complex based-dye N719, and an electrolyte in the form of an oxidation-reduction (redox) couple I -/I-. The TiO photoanode and the rGO/PANI 3 2 composite counter electrode are applied in DSSC. The results showed rGO/PANI composite films were obtained with optimum performance with the weight composition of 4:1, which reached an efficiency of 2.64%. The second step in developing rGO/PANI counter electrodes is the direct synthesis between rGO and aniline using in situ polymerization. The synthesis method used is the stirring method at 0 ° C for 24 hours. In the synthesis of rGO, two types of rGO are produced, the precipitated rGO (PrGO) and floated-rGO (FrGO). Both types of rGO are polymerized in situ with PANI to produce PANI- PrGO and PANI-FrGO composites. Both types of rGO/PANI composites were applied as counter electrodes on DSSC using the same deposition that was screen printing technique. However, rGO/PANI film produced by in-situ polymerization has the disadvantage of being easy to peel, due to the weak interaction between rGO and synthetic graphite substrate. Therefore, to overcome this, graphite is blended to the rGO/PANI composite with a composition of 3:1 to improve interactions with the synthetic graphite substrates and increase the composite electrical conductivity. Performance test results with solar simulators show that graphite/PANI-PrGO has a better performance than graphite/pure PANI and graphite/PANI-FrGO. Graphite/PANI-FrGO counter electrode has an efficiency of 1.14%, while graphite/PANI-PrGO has an efficiency of 1.83%. The third step of the development of graphite/PANI-PrGO composite was carried out to obtain the better performance of the counter electrodes with electrolyte doping. Electrolytes were added to the ethanol/distilled water solution with a volume composition of 1:1, which consist of 10 mL of ethanol and 10 mL of distilled water, which then was used to make the methylcellulose paste as a binder in preparing the graphite/PANI-PrGO composite paste. Electrolytes added in composition of 0, 5, 10, 15, and 20%. DSSC cell performance results with electrolyte doped graphite/PANI-PrGO counter electrode showed a significant increase in Jsc and efficiency from 1.83% without electrolyte doping to 3.02% after electrolyte doping by 10% doping. The final step in the research of this dissertation is the stage of photoanode development. Photoanode is almost usually made of TiO2 J25 material. However, to improve photoanodes' ability to harvest photons, some recent research results use a mixture of materials with similar characters and have a larger particle size. In this dissertation, a study using SiO2 microbeads as a mixture of TiO2 with SiO2 weight composition of 0, 5, 10, 15, 20% was done. The TiO2-SiO2 photoanode film was then coupled with the graphite/rGO-PANI film counter electrode to be applied as DSSC. DSSC cell performance results with solar simulators showed a significant increase in Jsc and efficiency, from 6.52 to 8.11 mA/cm2 and 2.06 to 2.81% with 10% SiO2, respectively. rGO/PANI, graphite/PANI-PrGO, electrolyte doped graphite/PANI-PrGO became potential material as a substitute electrode for Pt. While in TiO2-SiO2 photoanodes, the presence of SiO2 increase the catalytic activity of photoanodes. SiO2 has good thermal stability, good mechanical strength, and helps to create active catalytic sites on photoanodes due to the interaction between TiO2 and SiO2.