Tunnel Junctions for III-V Multijunction Solar Cells Review

Abstract

Tunnel Junctions, as addressed in this review, are conductive, optically transparent semiconductor layers used to join different semiconductor materials in order to increase overall device efficiency. The first monolithic multi-junction solar cell was grown in 1980 at NCSU and utilized an AlGaAs/AlGaAs tunnel junction. In the last 4 decades both the development and analysis of tunnel junction structures and their application to multi-junction solar cells has resulted in significant performance gains. In this review we will first make note of significant studies of III-V tunnel junction materials and performance, then discuss their incorporation into cells and modeling of their characteristics. A Recent study implicating thermally activated compensation of highly doped semiconductors by native defects rather than dopant diffusion in tunnel junction thermal degradation will be discussed. AlGaAs/InGaP tunnel junctions, showing both high current capability and high transparency (high bandgap), are the current standard for space applications. Of significant note is a variant of this structure containing a quantum well interface showing the best performance to date. This has been studied by several groups and will be discussed at length in order to show a path to future improvements.

Challenges for the future of tandem photovoltaics on the path to terawatt levels: a technology review

“…Progressively increasing the voltage leads to an increase in the energy misalignment between the available states for tunneling, causing a decrease in the current density, effectively leading to a negative resistance region. With a further increase in voltage, the tunnel junction starts behaving as a conventional diode, as the flattening bands lead to the typical exponential diode diffusion current [65,[85][86][87]. current density of the device.…”

Role of earth-abundant selenium in different types of solar cells

“…Multijunction solar cells are constructed by stacking semiconductors with varying bandgaps on top of one another, thereby allowing the cell to absorb differing wavelengths of solar radiation. The tunnel junction enables metal-to-metal electrical connectivity, which can also be achieved through an indium film processable at room temperature under low pressure [3]. Multijunction solar devices use a high-bandgap top cell to absorb high-energy photons while allowing the lower-energy photons to pass through.…”

Solar energy harvesting for LoRaWAN-based pervasive environmental monitoring

“…Some studies [23], [24], [25], [26], [27], [28], [29] aim to enhance the performances under particular light spectrum conditions, mainly low-intensity indoor lighting, choosing materials with suitable absorption spectra. Other researches focus on extremely improving the efficiency by realising multijunction structures capable of absorbing energy in a wide frequency range [30], [31].…”