Technical Brief

Efficiency Estimations for Multijunction and Intermediate Band Solar Cells Using Actual Measured Solar Spectra in Japan

[+] Author and Article Information
Shunya Naitoh

School of Engineering,
The University of Tokyo,
7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-8656, Japan;
Research Center for Advanced Science and Technology (RCAST),
The University of Tokyo,
4-6-1 Komaba,
Meguro-ku, Tokyo 153-8904, Japan
e-mail: naito@mbe.rcast.u-tokyo.ac.jp

Yoshitaka Okada

School of Engineering,
The University of Tokyo,
7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-8656, Japan;
Research Center for Advanced Science and Technology (RCAST),
The University of Tokyo,
4-6-1 Komaba,
Meguro-ku, Tokyo 153-8904, Japan
e-mail: okada@mbe.rcast.u-tokyo.ac.jp

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 October 5, 2014; final manuscript received November 27, 2014; published online January 15, 2015. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 137(3), 034504 (Jun 01, 2015) (4 pages) Paper No: SOL-14-1283; doi: 10.1115/1.4029382 History: Received October 05, 2014; Revised November 27, 2014; Online January 15, 2015

An intermediate band solar cell (IBSC) whose equivalent circuit is similar to a multijunction (MJ) solar cell but with an additional parallel diode connection is shown to be more robust to spectral variation than a series-connected MJ solar cell. We have calculated the limiting efficiencies of IBSC and MJ solar cells using the measured solar spectra in Japan. Even though the maximum efficiency of an IBSC is lower than a triple junction (3J) solar cell at airmass (AM)1.5, the IBSC would generate more annual electricity by 1% than 3J cell at 1 sun, if they had been optimized at AM1.5.

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Grahic Jump Location
Fig. 4

Relative photon absorption with AM1.5 in each 3J solar cell at 1 sun and AM at Gifu in 2008

Grahic Jump Location
Fig. 3

The calculated average efficiency of each solar cell at 1 sun in each month at Gifu in 2008

Grahic Jump Location
Fig. 2

The variation of calculated efficiency and cell temperature (Tc) of each solar cell during a clear day at Gifu on December 10, 2008

Grahic Jump Location
Fig. 1

Schematic diagram of (a) Se-connected and (b) Se/Pa-connected 3J solar cell. In the figure, (Eg,1, Eg,2, Eg,3) and (Eg,1′, Eg,2′, Eg,3′) are the bandgaps of the top, middle, and bottom subcells. The relation among the bandgap values are Eg,1 > Eg,2 > Eg,3 and Eg,1′ > Eg,2′ > Eg,3′.



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