Photovoltaic characteristics of each subcell evaluated in situ in a triple-junction solar cell. (December 2016)

• Record Type: Journal Article
• Authors: Huang, Tzu-Hsuan; Lo, Hao; Lo, Chieh; Wu, Meng-Chyi; Lour, Wen-Shiung
• Is Part Of: Solid-state electronics. Volume 126(2016)
• Page Start: 109
• Page End: 114
• Publication Date: 2016-12
• Subjects: Solar cell -- InGaP -- Ge -- Conversion efficiency; Semiconductors -- Periodicals; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.sse.2016.09.006
• Languages: English
• ISSNs: 0038-1101

Abstract

Highlights: The aim of work analyzed the fabrication of each junction-type solar cells. The InGaP-subcell exhibits the largest temperature coefficient (−2.5 mV/°C) of Voc . The JSC in the triple-junction solar cell is limited by the InGaP-subcell. The Ge-subcell promotes the 39% of overall reduction in the conversion efficiency. Abstract: New manufacturing processes were proposed to evaluate important photovoltaic properties of each subcell in an InGaP/InGaAs/Ge triple-junction solar cell. In addition to the triple-junction cell, an InGaAs/Ge double-junction cell and a Ge single-junction cell were also fabricated and employed for evaluation. The key merit of the double-junction cell is that semiconductor layers of forming InGaP top subcell are retained as a dummy top subcell. Thus, the InGaAs middle subcells in both triple- and double-junction cells will receive the same light spectrum. Similarly, the Ge single-junction cell is fabricated with dummy top and middle subcells as light filters. Open-circuit voltage, short-circuit current, conversion efficiency, and current mismatched ratio were measured for evaluating and optimizing each subcell. It is found that Open-circuit voltages are 1.295, 0.967, and 0.212 V for the InGaP, InGaAs, and Ge subcells with temperature coefficients of −2.5, −1.99, and −1.87 mV/°C. Thus the Ge subcell no longer acts a real solar cell at temperature over ∼140 °C. Besides, effect of ambient temperature on short circuit currents of all as-fabricated solar cells is not relevant. The current mismatched ratios are 18.6–20% at temperature ranged from 25 °C to 80 °C. A low efficiency of ∼18.7% is due partly to the poor current match. However, the processing concept proposed is useful as a method of matching currents among the subcells.