Compensation of self-absorption losses in luminescent solar concentrators by increasing luminophore concentration

Zachar Krumer,Wilfried G.J.H.M Van Sark,Ruud E.I Schropp,Celso De Mello Donegá

doi:10.1016/j.solmat.2017.04.010

Zachar Krumer, Wilfried G.J.H.M Van Sark + Show 2 more

Open Access

https://doi.org/10.1016/j.solmat.2017.04.010

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Abstract

Self-absorption in luminophores is considered a major obstacle on the way towards efficient luminescent solar concentrators (LSCs). It is commonly expected that upon increasing luminophore concentration in an LSC the absorption of the luminophores increases as well and therefore self-absorption losses will have higher impact on the performance of the device. In this work we construct a fully functioning liquid phase LSC where the luminophore concentration can be altered without changing other conditions in the experimental set-up. We step-wise enlarge the concentration of the luminophores Lumogen Red 305 and Lumogen Orange 240, while monitoring the electrical output and self-absorption effects. Contrary to common belief, self-absorption does not increasingly limit the performance of LSCs when the luminophore concentration increases.

Highlights

Luminescent solar concentrators (LSCs) are photovoltaic devices whose goal is to reduce the necessary amount of active photovoltaic elements per Watt of delivered power by means of concentration [1]
The monitoring of LSC performance and effects of self- absorption at various concentrations was carried out in two experiments: operation of a fully functional liquid phase prototype (Section 2.2) and spectroscopy at variable optical path lengths (Section 2.3). In both experiments the luminophore concentration was changed in a controlled way, such that data from both experiments was retrieved for the same range of luminophore concentrations
This saturation is expected from the Lambert-Beer law: A = 1 − 10−εcx which states that the fraction of absorbed light A increases and saturates as the dye concentration c at a constant absorption coefficient ε and a constant optical path x

Summary

Introduction

Luminescent solar concentrators (LSCs) are photovoltaic devices whose goal is to reduce the necessary amount of active photovoltaic elements per Watt of delivered power by means of concentration [1]. The LSC device is essentially a thin transparent plate, within which luminescent species (luminophores) are dispersed (Fig. 1). Solar radiation enters the LSC through the large top surface and is absorbed by the luminophores. A large fraction of the isotropically emitted light hits the inner surface of the transparent plate in the regime of total internal reflection and is trapped inside the transparent plate. The trapped light is waveguided to the edges of the plate, where solar cells are attached and conversion into electricity takes place. Concentration arises from the projection of light entering through the large top surface onto the small solar cell surface, which makes it possible to harvest much more light per unit of semiconductor material. This concentrator concept does not require bulky tracking devices and allows greater freedom when it comes to form, which makes it well suited for building integration of low-concentration photovoltaics [2,3,4,5]

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