Application of Quantum Dots to Solar Cells to Increase Efficiency
- PDF / 2,215,660 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 232 Views
Application of Quantum Dots to Solar Cells to Increase Efficiency Chris Botros and Richard Savage California Polytechnic State University, San Luis Obispo Materials Engineering, 1 Grand Ave, Bldg. 41-230, San Luis Obispo, CA 93407, U.S.A. ABSTRACT The goal of this work is to increase the efficiency of conventional solar cells by incorporating quantum dot (QD) nanoparticles in the absorption mechanism. The strategy is to have the QDs absorb UV and fluoresce photons in the visible region that are more readily absorbed by the cells. The outcome is that the cells have more visible photons to absorb and have increased power output. The QDs, having a CdSe core and a ZnS shell, were applied to the solar cells as follows: (1) The QDs were first synthesized in a solution. (2) They were then removed from the solution and dried. (3) The dried QDs are then deposited into polydimethylsiloxane (PDMS) and the PDMS/QD composite is allowed to cure. (4) The cured sample is applied to a silicon solar panel. The panel with the PDMS/QD application outputs 2.5% more power than the one without, under identical AM1.5 illumination using QDs that fluoresce in the orange region. This work demonstrates the feasibility of incorporating QDs to increase the efficiency of conventional solar cells. Because the cells absorb better in the red region, future effort will be to use QDs that fluoresce in that region to further boost cell output. . INTRODUCTION Thermodynamic efficiency limits the power output of a solar cell due to the Carnot limit and the band gap associated with the solar cell. Photons with energy greater than the band gap will cause an electron to be excited to the conduction band and then relax to the valence band, with the excess energy being released as heat. [1] With increasing temperature, the solar cell will suffer from heat-related energy losses due to increases in resistance.[2] For the reasons just stated, solar cell performance increases when irradiated with photons within the region most readily absorbed by the solar cells. Quantum dots (QDs) can absorb photons with energy greater than the band gap and fluoresce photons with energies closer to the band-gap [3]. In doing so, the solar cell is much cooler since much of the excess energy from high energy photons no longer results in heat. Although the QDs will exhibit an increase in heat as they absorb photons with energy greater than their band gap, their very large surface area to volume ratio results in much faster heat dissipation and prevents heat accumulation in the cell. In order to apply QDs to the solar cell, they must be deposited into a material that will act as a carrier. This research uses PDMS due to its malleability, availability, and low cost. The QDs are synthesized so they fluoresce at or near the band gap of the solar cell and than they are deposited into PDMS which is then applied to the solar cell. EXPERIMENT This work uses QDs with a CdSe core and a ZnS shell. The quantum dots used in this research are ones synthesized using a process developed at Californ
Data Loading...
