Grantee Research Project Results
Final Report: Manufacture of Photovoltaic Solar Cell Using Plant Chlorophyll
EPA Grant Number: SU833536Title: Manufacture of Photovoltaic Solar Cell Using Plant Chlorophyll
Investigators: Gao, Ning , Lenanyokie, Alice , Kozlowski, Andrew , Holland, Camden , Webster, Caroline , Rosales, Jon , Carr, Reed
Institution: St Lawrence University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 30, 2007 through August 29, 2008
Project Amount: $8,089
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2007) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Awards , Sustainable and Healthy Communities
Objective:
The main objective of this project is to manufacture a TiO2 based photovoltaic (PV) solar cell using chlorophyll from spinach leaves (a mixture of chlorophyll a and b). Then, a comparison of such a TiO2 based, chlorophyll sensitized solar cell will be made with solar cells with only chlorophyll a or chlorophyll b (as illustrated in the main reference used in our Phase I proposal: Aoki et al., 2005). Our hypothesis was that a mixture of chlorophyll a and b, extracted from spinach leaves or other plants with a high chlorophyll content, would yield better solar energy conversion efficiency due to the combined absorption bands of both forms of chlorophyll.
Summary/Accomplishments (Outputs/Outcomes):
To date, we have successfully manufactured working chlorophyll sensitized solar cells using chlorophyll (and b mixture) from spinach leaves. We have evaluated the electronic characteristics (voltage, current, and power outputs using different loading resistors) of this solar cell against a TiO2 control cell without a chlorophyll sensitizer under two different sets of light exposure (indoors with a white bulb; and outdoors with natural sunlight, and over the course of three weeks). The solar energy conversion efficiencies were obtained for different illuminating conditions. The results show that the chlorophyll sensitized TiO2 based solar cell yielded 20 times higher maximum power when exposed to outdoor natural sunlight, and 45 times higher maximum power when exposed to a 40W white bulb compared with the non-sensitized control TiO2 cell. This is a clear indication that the chlorophyll has indeed sensitized the solar cell by allowing the solar cell to absorb the visible light range, whereas the non-sensitized TiO2 cell absorbs mainly in UV range. The monitoring of the performance of the solar cell over the course of three weeks provided important data on its viability. Manufacture of more chlorophyll-TiO2 solar cells is underway to enable more systematic evaluation of these cells under the experimental conditions originally proposed. Manufacture of solar cells with chlorophyll a or b, as shown in Aoki et al. 2005, will be carried out this summer to allow for the comparison study originally proposed.
Conclusions:
To date, the Phase I project has achieved the proposed objectives, and the outcomes are quite positive. We will continue to work on the remaining tasks of Phase I during the rest of the funding period to collect more experimental data and to conduct additional systematic testing to prepare for Phase II of the project.
Proposed Phase II Objectives and Strategies:
Phase II of this project will proceed with a two-fold focus: 1) to research ways to improve energy conversion efficiency and long-term viability of the chlorophyll sensitized TiO2 based solar cells; and 2) to research the feasibility of using metallacrowns as the sensitizer to fabricate TiO2 based solar cells.
The study conducted in Phase I of this project demonstrates the potential for chlorophyll sensitized TiO2 based solar cells to become a viable electrical power source. Although the solar cells produced in this study were a relatively crude device, they nonetheless show electrical performance in line with recently published results from a couple of other studies. Our Phase I study has identified several areas for improvements that could be made to improve significantly the energy conversion efficiency and lantern viability of this type of solar cells. To make our Phase II effort more productive, we will also take into account recent published studies done at other institutions on chlorophyll sensitized solar cells and other types of organic dye sensitized solar cells. We will steer our effort into areas that show promise, but have not yet been explored or closely examined by other research groups. The five main objectives for our Phase II project are:
- To improve the energy conversion efficiency of the chlorophyll sensitized solar cells by synthesizing and testing different types of derivatives of chlorophyll that may expand the absorption wavelength range of the solar cells.
- To improve the long-term viability of the chlorophyll sensitized solar cells by testing alternative electrolytes that will not degrade chlorophyll, including solution phase and solid phase electrolytes.
- To improve the cost effectiveness of these solar cells by testing alternative materials that could replace one of the two electrodes that doesn’t have to be transparent. To date, all the known TiO2 based solar cells are made of expensive transparent conductive oxide (TCO) glass slides as both electrodes. We propose to replace the electrode that doesn’t have to be transparent and replace it with a highly conductive, rigid, less reactive, less expensive, and light-weight material, e.g., aluminum. The added advantage of replacing one of the two glass slides in the solar cell with a rigid material (metal) would greatly enhance the durability of the solar cell and make it more viable as a building material (roof or siding).
- To study the feasibility of using metallacrowns as the sensitizer for the TiO2 based solar cells. Certain types of metallacrowns, such as the copper complex with a macrocyclic structure, possess electrochemical and photochemical properties similar to porphyrin-type organic sensitizers (e.g., chlorophyll). Such types of metallacrowns have a metal ion center that can go through reversible reduction and oxidation (i.e., capable of electron transfer); and they have significant absorption in both the near-uv range and the visible light range. The metallacrowns have advantages over synthetic porphyrin-type organic sensitizers, including the ease for synthesis.
- To manufacture the prototype solar cells based on the improved design. We propose to work with the St. Lawrence University Environmental Action Organization, Coalition on Climate Change, and the local Community Energy Service to conduct field tests of these solar cells and to study the feasibility of commercialization of these solar cells.
Supplemental Keywords:
Chlorophyll, solar cell, PV cell, metallacrown,, RFA, Air, climate change, Air Pollution Effects, AtmosphereThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.