Novel heterojunction bipolar transistor architectures for the practical implementation of high-efficiency three-terminal solar cells

Steiner

et al. 2020

Preprint

Self Cite

We demonstrate a novel multijunction architecture, the heterojunction bipolar transistor solar cell (HBTSC), which exhibits the performance of a double-junction solar cell in a more compact npn (or pnp) semiconductor structure. The HBTSC concept has the advantages of being a three-terminal device, such as low spectral sensitivity and high tolerance to non-optimal band gap energies, while it reduces the fabrication and operation complexity with respect to other multi-terminal devices because, for example, it can produce independent power extraction from the two junctions without the need for extra layers for their isolation or inter-connection. The top and bottom junctions in our proof-of-concept HBTSC prototype, which is made of epitaxial GaInP/GaAs, exhibit independent current-voltage characteristics under AM1.5G illumination, with respective open-circuit voltages of 1.33 and 0.95 V. The voltage difference between the two junctions is notable considering that they share a thin (< 600 nm) GaInP layer which contributes to the photogeneration of both junctions. This can be explained by a gradient in the minority carrier quasi-Fermi level within the base layer, which is compatible with a high fill factor. We also offer a technological solution for contacting the intermediate layer and study the effect of series resistance on the device performance. The HBTSC opens a new perspective in the understanding of multi-junction devices and it is an excellent candidate for the application of low-cost fabrication techniques, and for the implementation of III-V on silicon tandems with parallel/series interconnection for high energy yield.

Section: Main Textmentioning

confidence: 99%

GaInP/GaAs three-terminal heterojunction bipolar transistor solar cell

Steiner

et al. 2020

Preprint

Self Cite

“…The concept is especially useful for emerging technologies in which the fabrication of a tunnel junction can be challenging, such as nanowire devices, or when low‐cost epitaxial growth techniques are employed. Practical implementations of the 3T‐HBTSC have been proposed based on III–V compounds, 4 earth‐abundant kesterites, 5 nanowires, 6,7 and perovskite/silicon 6,8,9 …”

Section: Introductionmentioning

confidence: 99%

“…3 The concept is especially useful for emerging technologies in which the fabrication of a tunnel junction can be challenging, such as nanowire devices, or when low-cost epitaxial growth techniques are employed. Practical implementations of the 3T-HBTSC have been proposed based on III-V compounds, 4 earthabundant kesterites, 5 nanowires, 6,7 and perovskite/silicon. 6,8,9 What makes the transistor solar cell concept different from other three-terminal architectures [10][11][12] is the fact that the minority carrier transport through the base is not interrupted, meaning that a majority carrier injected from the emitter into the base (and therefore, becoming a minority carrier in this region) has the potential of reaching the collector, as it is described in the theoretical framework of bipolar transistors.…”

Section: Introductionmentioning

confidence: 99%

Progress in three‐terminal heterojunction bipolar transistor solar cells

Antolín

Progress in Photovoltaics

et al. 2022

Self Cite

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 doublejunction 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.

“…Different designs of HBTSCs including emerging low-cost materials, such as metal-halide perovskites or nanowires, have already been proposed. [29][30][31][32] Stringing of multi-terminal devices is also an important challenge that we discuss at the end of the paper, with emphasis on an option that allows the integration of HBTSCs into modules eliminating complex stringing and the extra cost that it could introduce.…”

Section: Toc Graphic Introductionmentioning

confidence: 99%

GaInP/GaAs three-terminal heterojunction bipolar transistor solar cell

Steiner

et al. 2021

Preprint

Self Cite

We demonstrate a heterojunction bipolar transistor solar cell (HBTSC), a device that exhibits the performance of a double-junction solar cell in a more compact npn (or pnp) semiconductor structure. The HBTSC concept has the advantages of being a three-terminal device, such as low spectral sensitivity and high tolerance to non-optimal band-gap energies, while it has a lower fabrication and operation complexity than other multi-terminal architectures: it can produce independent power extraction from the two junctions without the need for extra isolating or interconnecting layers between them. The two junctions in our proof-of-concept HBTSC prototype, which is made of epitaxial GaInP/GaAs, exhibit independent current-voltage characteristics under AM1.5G illumination, with respective open-circuit voltages of 1.33 and 0.95 V. The HBTSC opens a new perspective in the understanding of multi-junction devices, and it is an excellent candidate for the application of low-cost fabrication techniques, and for the implementation of III-V-on-silicon tandems.