Progress in three‐terminal heterojunction bipolar transistor solar cells

• Published in: Progress in photovoltaics 2022-08, Vol.30 (8), p.843-850
• Main Authors: Antolín, Elisa, Zehender, Marius H., Svatek, Simon A., Steiner, Myles A., Martínez, Mario, García, Iván, García‐Linares, Pablo, Warren, Emily L., Tamboli, Adele C., Martí, Antonio
• Format: Article
• Language: English
• Subjects: base transport factor; bottom interdigitated contact; emitter injection efficiency; heterojunction bipolar transistor solar cell; Heterojunction bipolar transistors; III-V material; multijunction solar cell; P-n junctions; Photovoltaic cells; Semiconductor devices; Solar cells; SOLAR ENERGY; tandem solar cell; Tunnel junctions
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.3536

Conventional solar cells, including multijunction solar cells, are based on pn junctions as building blocks. In contrast, the three‐terminal heterojunction bipolar transistor solar cell (3T‐HBTSC) explores the use of a bipolar transistor structure to build a solar cell. The limiting efficiency of this transistor structure equals that of a double‐junction solar cell. However, since the 3T‐HBTSC does not require tunnel junctions, its minimal structure has only three semiconductor layers, while the minimal structure of a double junction solar cell has six. This work reviews the operation principles of this solar cell and the steps carried out towards its practical implementation. Experimental results on a GaInP/GaAs HBTSC prototype with bottom interdigitated contacts are presented. The concept of three‐terminal heterojunction bipolar transistor solar cell (HBTSC) is reviewed, a device with a more compact structure than the double‐junction solar cell which exhibits the same efficiency limit. We explain how a two‐terminal triple‐junction solar cell can be built by combining an HBTSC and a bottom silicon cell. We provide the experimental proof of concept of a GaInP/GaAs HBTSC with bottom interdigitated contacts.