Energy Relay Dye Dynamics With Highly Purified Chlorophyll A as Photo-sensitizer
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Energy Relay Dye Dynamics With Highly Purified Chlorophyll A as Photo-sensitizer Komal Magsi1,2, Ping Lee1,2, Yeona Kang 1,2, , and Charles M. Fortmann1,2 1
Materials Science Department, Stony Brook University, Stony Brook, NY, 11790, U.S.A. 2
Idalia Solar Technologies, 270 Lafayette St. Suite 1402 New York, NY, 10012, U.S.A.
ABSTRACT Dye type solar cells, especially those incorporating low cost dyes suffer from a very narrow photo-response wavelength range. Motivated by natural photosynthesis research, energy relay dyes (ERDs) appear to offer a possibility to broaden the dye-cell spectral response. In-turn photovoltaic cells can be an extremely sensitive tool for investigation of dye ERD photochemistry. Sensitive Chlorophyll based dye-type solar cells were prepared from purified natural Chlorophyll A. The importance of Chlorophyll purity is discussed as well as the use of purified Chlorophyll A in combination with ERD’s. . Results shed light on many interesting phenomenon including the nature of purified Chlorophyll A excitation and absorption. Importantly, it was found by this work that the ERD architecture when combined with a photosensitizer do not appear to having greater absorption in the infrared region of the spectrum than the ERD alone indicating a lack of cooperative absorption. INTRODUCTION Owing to the potential for reduced cost photovoltaic solar energy generation, dye-type solar cells have been the focus of intense research. [1] The theory of long range energy transfer of ERDs has recently been explored as a means to widen the photo-response wavelength range of DSCs. [2-6] Theoretical considerations suggest that ERDs absorb high-energy photons and transfer the energy through Forster resonance energy transfer (FRET) to the sensitizing dyes thereby broadening the spectral response. Conceptually, this theory is supported by the ability of the ERD to absorb in different parts of the solar spectrum. FRET involves dipole–dipole coupling of two chromophores, known as the donor and acceptor, through the electric field. It is argued that ERDs have a fundamentally different function and design from sensitizing dyes. That is, ERDs are thought to act only when coupled to a dye. Gratzel et al. proposed that ERDs may be able to strongly absorb the higher energy portion of the solar spectrum and efficiently transfer this energy to the sensitizing dye(s). [4] It was reported that the incorporation of commercially available 4-(dicyanomethylene)-2-methyl-6-(4dimethylaminostyryl)-4G-pyran (DCM) with the sensitizing dye, zinc phthalocyanine (TT1), exhibits an excitation transfer efficiency of over 95%. [4] In this work, DCM and Rhodamine B (RB) are incorporated as ERDs. The sensitizing dye employed in this work was purified Chlorophyll A (C55H72MgN4O5) extracted from natural spinach leaves. Purification involved rotary evaporation and column chromatography. The purpose of our study is to: 1) understand whether the concept of ERD is universal to all sensitizing dyes and 2) analyze the quantum efficiency properties of th
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