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Phase 5 (2012 Deadline)
New Approaches for Lower Cost, Longer Ability and Higher Efficiency of Dye-Sensitized Solar Cells (DSSCs) Qiquan Qiao, South Dakota State University
Muhammad Hassan Sayad, Ghulam Ishaq Khan Institute of Engineering, Sciences and Technology Project Overview Pakistan is a developing country that has suffered severe energy deficiency over the last few years. Unfortunately, this energy deficiency continues to amplify, adversely affecting commercial and economic activities, as well as quality of life. The need for cost-effective solar energy grows increasingly urgent as the demand for and price of power continues to rise and the global warming caused by fossil fuel combustion escalates. Solar energy is an unlimited form of clean and renewable energy that is abundantly available in Pakistan. The goals of this project are to develop next generation dye-sensitized solar cells (DSSCs) with lower cost, longer stability, and higher efficiency, and to provide research training in both countries to students and postdoctoral scientists in the field of solar energy. Progress Reports 2014: The team has improved solar to electricity conversion efficiency by using new approaches such as the incorporation of semiconductor nanoparticles into semiconductor nanofibers as photoanode to increase the surface area for more light-absorbing material attachment. In addition, they also used carbon nanofiber/semiconductor nanoparticle composite counter electrode as a replacement to Pt to lower the cost of dye-sensitized solar cells (DSSCs). Training of undergraduate and graduate level students in this field was extensive in the last year. Dr. Sayyad’s team appointed eight undergraduate and two PhD students to work on this project. He also supervised two final year projects related to dye-sensitized solar cells. Devices derived from these final year projects along with presentation posters were exhibited at the GIKI 2014 Open House and Career Fair held in April 2014. Dr. Qiao recruited two Masters students and one PhD student to participate in the project, and two academic courses on organic photovoltaics and advanced electronic materials were created at SDSU. These two courses can reach out to 10-15 graduate students. Dr. Qiao visited GIKI in December 2013 to attend and speak at the 2013 GIKI-SDSU International Symposium on the Design of Dye-Sensitized Solar Cells for Cost Effective Solar Energy Harvesting. Jointly organized by Drs. Sayyad and Qaoi, the symposium brought together about 150 scholars, including seven invited speakers, 110 students, and 30 faculty members from all parts of Pakistan. Dr. Sayyad gave two seminars at the symposium. He himself visited South Dakota State University in June 2014 where he held discussions with the U.S. team about the fabrication, testing, and optimization of DSSCs and ideas for future research collaboration. Dr. Sayyad was also given a tour of the Research Laboratories of the Center for Advanced Photovoltaics and examined the use of some new experimental facilities there. Outreach on this project was not limited to the SDSU-GIKI Symposium. During the last year Dr. Sayyad delivered a presentation on this project at the Science, Technology & Engineering for Development International Conference in June in Islamabad. A month later he gave a talk at the International Conference on “Nanoscience and Nanotechnology for Next Generation (NanoNG14)” at Firat University in Turkey. Dr. Qiao contributed four articles on dye-sensitized solar cells to various journals including the Journal of Materials Chemistry A, and the Institute of Electrical and Electronics Engineers Electron Device Letters. He also spoke about the development of cost effective solar cells at Jilin University and Changchun Institute of Applied Chemistry in July in China. 2015: During the second year of this project, the Pakistani PI, in collaboration with the US PI, arranged the “2015 GIKI-SDSU International Seminar on Alternative Energy Solutions for Pakistan" held at the Faculty of Engineering Sciences, GIKI Institute of Engineering Sciences and Technology, Topi, Pakistan, on May 02, 2015.
On the technical side, the team has developed porous hollow tin oxide (SnO2) nanofibers and their composite with titanium dioxide (TiO2) particles (Degussa P25) as a photoanode for dye-sensitized solar cells (DSSCs). Incorporation of TiO2 particles in porous hollow SnO2 fibers enhanced the power conversion efficiency (η) from 4.06% to 5.72% under 100 mW/cm2 light intensity. The enhancement of efficiency was mainly attributed to an increase in current density (Jsc) and improvement in fill factor (FF). The increase in Jsc was caused by higher dye loading as indicated by UV-Vis absorption spectra and the improvement in fill factor was attributed to faster charge transport time as obtained from transient analysis. In addition, novel porous three dimensional (3D) hierarchical graphene-beaded carbon nanofibers with incorporated Ni nanoparticles (G/CNFs-Ni) were used for the first time as cost-effective counter electrode for dye-sensitized solar cells (DSCs). The G/CNFs-Ni composite exhibited an overall power conversion efficiency of 7.14 % as compared to 7.59 % for reference platinum (Pt) counter electrodes.
2016: The objectives of this project are to develop next generation dye-sensitized solar cells (DSSCs) with lower cost, longer stability, and higher efficiency, and to provide research training in both countries to students and postdoctoral scientists in the field of solar energy. During the third year of this project, the Pak PI in collaboration with the US PI organized the "2016 INTERNATIONAL CONFERENCE ON NEXT GENERATION ENERGY TECHNOLOGIES (ICONGET 2016) & WORKSHOP ON SOLAR CELL CHARACTERIZATION TECHNOLOGY" held at the Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi, Pakistan, on April 1-3, 2016. On the technical side, the US team has developed metal oxides (e.g., MoO3, ZnO and V2O5) based counter electrodes for dye-sensitized solar cells (DSSCs). They characterized low cost metal oxides (e.g., MoO3, ZnO and V2O5) based counter electrodes and tested solar cell energy conversion efficiency. They also optimized DSSC fabrication procedures (e.g., counter electrode thickness and annealing temperatures) to increase energy conversion efficiency. In addition, the US team developed urea-treated commercial iodide-triiodide electrolyte to improve the overall efficiency. The Pakistan team has synthesized AZO and donor-porphyrin- acceptor type dyes for stable and higher efficiency of DSSCs. Photovoltaic performance of fresh and one-year-old AZO dye based DSSCs were compared. They synthesized electrolyte for quantum dot DSSCs (QDSSCs), which exhibited enhanced performance. One Pakistani PhD student visited the USA to carry out the joint research.
2017: There is increasing global interest in alternative forms of energy, and sunlight is a particularly promising clean and readily available source compared with conventional fossil fuels. Perovskite solar cell is a new entry in the line of next generation solar cells, with rapidly increasing performance getting close to those of silicon solar cells. In the last year we have been working on improving the power conversion efficiency of dye-sensitized solar cells by using novel materials and techniques. We have introduced novel and low cost metal oxides materials to replace rare and expensive platinum as catalysts or counter electrodes. The novel technique was to reduce the different metal oxides such as WO3, SnO2, and ZnO with a reducing agent such as urea. By optimizing urea content as dopant in metal oxides, we successfully obtained the optimum catalytic performance towards iodide/triiodide electrolyte. The power conversion efficiency value of DSSCs of ~ 11 % was obtained which was much higher compared to the device power conversion efficiency fabricated with Pt-based counter electrode with ~ 8.5%. Another novel technique which significantly improved the overall power conversion efficiency of dye-sensitized solar cells (DSSCs) was to apply urea directly to the iodide/triiodide electrolyte. Applying urea to the electrolyte induced a significant increase in both open circuit voltage (VOC) and fill factor (FF). The improvement was attributed to the lower back recombination of photo generated electrons with electrolyte as a result of lower concentration of triiodide ions in the mesoporous TiO2. A similar technique was studied by doping iodide/triiodide electrolyte with reduced graphene oxide (rGO). The power conversion efficiency of DSSCs was increased after doping electrolyte with rGO and this increase was attributed to rGO facilitating the charge transfer for efficient electrolyte reduction and hence better device performance.
2018: In summary, we have fabricated dye-sensitized solar cells (DSSCs) using Biochar as counter electrode and achieved acceptable photo-conversion efficiency compared to the devices using Pt as control counter electrode. Two visiting Pakistani students including Ramshah Ahmad and Afaq Ali has received extensive training in DSSC fabrication, testing and optimization, which will help Pakistan to develop DSSC fabrication skill sets.
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