A new method to characterize bifacial solar cells

• Published in: Progress in photovoltaics Vol. 22; no. 8; pp. 903 - 909
• Main Authors: Singh, Jai Prakash, Walsh, Timothy M., Aberle, Armin G.
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01.08.2014; Wiley; Wiley Subscription Services, Inc
• Subjects: Applied sciences; bifacial efficiency; bifacial solar cell; Computational efficiency; Computing time; Design engineering; Energy; Exact sciences and technology; gain-efficiency product; Illumination; Mathematical analysis; Natural energy; Photovoltaic cells; Photovoltaic conversion; Sensitivity analysis; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; STC measurement; Performance evaluation; gain-efficiency product; Sensitivity analysis; Short circuit currents; Diode; STC measurement; Critical parameter; Fill factor; Open circuit voltage; bifacial solar cell; Solar cell; Standard test; Equivalent circuit; Illumination; bifacial efficiency; Gain; Electrical characteristic
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2341

ABSTRACT We present a new method to characterize bifacial solar cells under standard test conditions (STC). The method considers the bifacial operation of the cell and provides the characteristics for simultaneous front and rear side illumination rather than providing the front and the rear side characteristics separately. The method involves measurements of front side electrical parameters (efficiency, open‐circuit voltage, short‐circuit current and fill factor) and rear side short‐circuit current under STC. Two new parameters are introduced, namely bifacial 1.x efficiency (effective efficiency) and gain‐efficiency product, which are calculated from the measured STC parameters. The former provides information related to the cell design considering the bifacial operation, whereas the latter provides the end‐use benefits from the modules with bifacial cells for a particular installation. To calculate the bifacial 1.x efficiency and the gain‐efficiency product, a one‐diode solar cell equivalent circuit is used. Characteristic plots are shown for the newly introduced parameters as a function of rear‐side illumination for various example solar cells. A sensitivity analysis is performed to understand the influence of each single‐sided STC solar cell parameter on the newly introduced parameters. This sensitivity analysis shows that the fill factor and the rear‐to‐front current ratio are the most critical parameters for bifacial solar cells. Copyright © 2012 John Wiley & Sons, Ltd. The method characterizes the bifacial solar cells considering the bifacial operation, i.e. simultaneous front and rear side illumination. The method involves measurements of front side electrical parameters and rear side short‐circuit current under STC conditions. The new parameters, bifacial 1.x efficiency and gain‐efficiency product provides information related to the cell design and the end‐use benefits from the bifacial modules. The method shows that the fill factor and the rear‐to‐front current ratio are the most critical parameters for bifacial solar cells.