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Research Papers

# Efficiency Enhancement of GaAs Solar Cell Using Luminescent Down-Shifting Layer Consisting of (CdSe)ZnS Quantum Dots With Calculation and Experiment

[+] Author and Article Information
Youngkun Ahn

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
e-mail: rootahn@gmail.com

Jungyoon Kim

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
Green school, Korea University,
Seoul 136-713, Korea
e-mail: rokmckjy@kist.re.kr

Seongbum Shin

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
e-mail: Tigerwow12@gmail.com

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
e-mail: f06630@kist.re.kr

Young-Hwan Kim

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
e-mail: youngkim@kist.re.kr

Yong-Tae Kim

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
e-mail: ytkim@kist.re.kr

Seong-Il Kim

Center for Materials Architecturing,
Korea Institute of Science and Technology,
Seoul 136-791, Korea
Green school, Korea University,
Seoul 136-713, Korea
e-mail: s-ikim@kist.re.kr

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received January 21, 2014; final manuscript received September 10, 2014; published online October 23, 2014. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 137(2), 021011 (Oct 23, 2014) (7 pages) Paper No: SOL-14-1019; doi: 10.1115/1.4028700 History: Received January 21, 2014; Revised September 10, 2014

## Abstract

In this work, we report the efficiency enhancement of a GaAs solar cell by using a luminescent down-shifting (LDS) layer consisting of (CdSe)ZnS quantum dots (QDs). The calculated conversion efficiency shows strong dependence on the luminescence quantum efficiency (LQE) and concentration of QDs in the LDS layer as well as the difference in external quantum efficiency (EQE) of the solar cell in the absorption and emission regions of the QD. Although the irradiance of the modified spectrum by the LDS layer was reduced with increases in QD concentration, the emission range of QDs in the spectrum was intensified. So the optimum parameters need to be calculated carefully. When we measured the GaAs solar cell with the LDS layer, it showed increased current density and consequently improved efficiency. The highest performance difference between the GaAs solar cell efficiencies with and without the LDS layer was over 2.8%, although a crystalline silicon solar cell below the LDS layer showed negative change in efficiency owing to its small EQE difference.

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## Figures

Fig. 1

(a) Normalized absorption and emission characteristics of the (CdSe)ZnS quantum dot. (b) Normalized EQE of the GaAs and c-Si solar cells. The absorption and emission plots are normalized for a peak value of unity.

Fig. 2

(a) Changes in the solar spectrum as a function of QD concentration in the LDS layer. (b) Irradiance as a function of QD concentration with different luminescent quantum efficiencies.

Fig. 3

Calculated maximum energy-conversion efficiency of the (a) GaAs and (b) c-Si solar cells as a function of QD concentration with various luminescent quantum efficiencies of QDs. While the energy-conversion efficiency of the GaAs solar cell was improved with the LDS layer, the c-Si solar cell showed negative effect of the LDS layer.

Fig. 4

Current density–voltage characteristics of the GaAs solar cell with and without LDS layers using two different host materials: (a) invisisil and (b) PDMS. Both cases show increased efficiencies when the LDS layer contained 30 μM of QD.

Fig. 5

Comparison of energy differences between calculation and experiment results

Fig. 6

Current density–voltage characteristics of the c-Si solar cell with the fabricated LDS layer. The short-circuit current decreased when the LDS layer was utilized.

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