Enhancing Photovoltaic Performance of GaAs Single-Junction Solar Cells by Applying a Spectral Conversion Layer Containing Eu-Doped and Yb/Er-Doped Phosphors.

Wen-Jeng Ho,Jheng-Jie Liu,Zong-Xian Lin,Hung-Pin Shiao

doi:10.3390/nano9111518

Wen-Jeng Ho, Jheng-Jie Liu + Show 2 more

Open Access

https://doi.org/10.3390/nano9111518

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Abstract

In this study, we examined efforts to increase the photovoltaic performance of GaAs single-junction solar cells using spectral conversion layers, respectively, composed of europium-doped (Eu-doped) phosphors, ytterbium/erbium-doped (Yb/Er-doped) phosphors, and a combination of Eu-doped and Yb/Er-doped phosphors. Spin-on film deposition was used to apply the conversion layers, all of which had a total phosphor concentration of 3 wt%. The chemical compositions of the phosphors were examined by energy-dispersive X-ray spectroscopy. The fluorescence emissions of the phosphors were confirmed by using photoluminescence measurements. Under laser diode excitation at 405 nm, we observed green luminescent downshift (LDS) emissions by Eu-doped phosphors at wavelengths of 479 nm to 557 nm, and under excitation at 980 nm, we observed red up-conversion (UC) emissions by Yb/Er-doped phosphors at wavelengths of 647 nm to 672 nm. The spectral conversion layers were characterized in terms of optical reflectance, external quantum efficiency, and photovoltaic current and voltage under AM 1.5 G simulations. The conversion efficiency of the cell combining Eu-doped and Yb/Er-doped phosphors (23.84%) exceeded that of the cell coated with Yb/Er-doped phosphors (23.72%), the cell coated with Eu-doped phosphors (23.19%), and the cell coated without phosphors (22.91%).

Highlights

Single-junction solar cells only convert photons with energy equal to and above the bandgap of the active material in the solar cells
This has led to the development of multiple bandgap tandem cells [7–11], intermediate bandgap cells [12–14], down-conversion (DC) cells [15–20], up-conversion (UC) cells [21–26], and luminescent downshifting (LDS) cells [27–30]
Nanomaterials 2019, 9, x FOR PEER REVIEW. This was followed by a 70 nm thick p-InGaP (5 × 1017 cm−3) back surface field (BSF) layer, a 100 nm Ntahniocmkatper-iGalsa2A01s9,(59, ×151108 17 cm−3) emitter layer, a 3200 nm thick n-GaAs (1 × 1015 cm−3) base layer, a 330ofn1m5 thick n-AlInP (5 × 1017 cm−3) front surface field (FSF) layer, and a 300 nm thick n+-GaAs (5 × 1018 cm−3) frcoonnttasuctrfalacyeefire. ldTh(FeSFq)ulaaylietyr, aonfd tah3e00epnimtatxhiaiclklna+y-eGrsaAwsa(s5 ×co1n0f1i8rmcme−d3)ucsoinntgactdloauybelre

Summary

Introduction

Single-junction solar cells only convert photons with energy equal to and above the bandgap of the active material in the solar cells. Luminescent-phosphors materials for DC, UC, and LDS, which are capable of converting a broad spectrum of light into photons of particular wavelengths, have been synthesized and used to minimize the losses in the photovoltaic device energy conversion process. The spectral conversion layer of UC cells is generally located on the bottom side of solar cells, as it is meant to modify photons that are not absorbed by the solar cell by shifting IR (infrared) and NIR (near infrared) parts of the spectrum to the visible part. We sought to enhance the photovoltaic performance of GaAs single-junction solar cells by applying spectral conversion layers, respectively, composed of europium-doped (Eu-doped) phosphors, ytterbium/erbium-doped (Yb/Er-doped) phosphors, and a combination of Eu-doped and Yb/Er-doped phosphors. We compared the efficacy of LDS- and UC-phosphors for enhancing conversion efficiency of GaAs single-junction solar cells

Experimental Details

Growth of Epitaxial Layer and Fabrication of GaAs Single-Junction Solar Cells

Results and Discussion

Conclusions