Optimized Metal-Free Back Reflectors for High-Efficiency Open Rear c-Si Solar Cells

Ingenito, A.; Luxembourg, Stefan L.; Spinelli, Pierpaolo; Liu, Ji; Ortiz Lizcano, JC; Weeber, A.W.; Isabella, O.; Zeman, M.

Optimized Metal-Free Back Reflectors for High-Efficiency Open Rear c-Si Solar Cells

Journal article (2015)

Authors

A. Ingenito Photovoltaic Materials and Devices -

Stefan L. Luxembourg ECN Solar Energy

Pierpaolo Spinelli ECN Solar Energy

Ji Liu ECN Solar Energy

JC Ortiz Lizcano External organisation

A.W. Weeber ECN Solar Energy

O. Isabella Photovoltaic Materials and Devices -

M. Zeman Photovoltaic Materials and Devices -

Research Group

Photovoltaic Materials and Devices () (TU Delft)

Light trapping White paint (WP) Bifacial solar cells Distributed Bragg reflectors

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Published Date

26-10-2015

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Electrical Sustainable Energy

Research Group

Photovoltaic Materials and Devices

Abstract

The photovoltaic (PV) industry has recently become more oriented toward n-type c-Si solar cells. Among the different n-type solar cell architectures, bifacial cells are quickly emerging. The open-rear configuration of a bifacial device results in high transmittance (T) losses at long wavelengths (>1000 nm). This limitation is usually overcome at the module level either by using a bifacial encapsulation or by placing a reflective foil on the rear side. In this paper, we have investigated the application of a distributed Bragg reflector (DBR) and TiO2-based white paint (WP) as alternative metal-free back-reflector options applied to the textured open-rear of bifacial n-Pasha cells. Because of the high T losses at long wavelengths of the DBR applied on textured surface, its design and fabrication is studied in detail. The dielectric (DBR and WP) and optimized Ag back-reflectors, which are used as a reference, are applied to bifacial n-Pasha cells, and their performance is evaluated. In particular, we demonstrate T below 20% at 1200 nm by optimizing the DBR thickness for textured surfaces. In addition, the optimized DBR and WP show performance comparable with a state-of-the-art Ag back-reflector. The highest increase of the conversion efficiency is measured for the WP back-reflector: +0.34% absolute compared with n-Pasha measured with no-additional back-reflector.