Numerical Analysis of Doped Plastic Optical Fibers as Sunlight Collectors for Solar Cells

The model and numerical results presented are mainly intended for researchers who are nowadays trying to design efficient and inexpensive solar concentrators for solar cells by using plastic optical fibers doped with suitable dyes. One issue discussed in this work is the feasibility or not of lengthening the doped fiber in order to collect more light. Another one is the feasibility of increasing the dopant concentration with the aim of favoring the absorption of the impinging sunlight. We clarify both issues, and we discuss the most suitable type of dye, by calculating the achievable electric power in each case.

I. Introduction

Some fluorescent molecules, such as coumarin-red, can not only absorb sunlight over a relatively broad range of wavelengths up to the red region, but also re-emit light at longer wavelengths, where the spectral responsivity of a typical silicon solar cell is greater. Furthermore, such molecules can be easily embedded in the core of a stretch of plastic optical fiber (POF) so that it will not only absorb part of the sunlight over its whole length, but also guide part of the re-emitted light to a solar cell [1]. If the type of dopant, the fiber length, and the dopant concentration are appropriate, the solar cell will deliver greater electric power than it would under direct exposition to the sun. Besides, POFs are inexpensive, and they do not need to be aligned towards the sun [2].