Gallium Nitride as Transparent Electron-Selective Contact in Silicon Heterojunction Solar Cells

Carrier-selective, passivating contacts have allowed silicon heterojunction (SHJ) cells to reach recordbreaking efficiencies particularly in all-back-contacted designs. However, two-side-contacted SHJ cell efficiency has been limited due in part to parasitic absorption losses up to 3 mA/cm2 in the aSi:H layers. More transparent materials could reduce this current loss while minimizing process complexity. Gallium nitride (GaN), with a bandgap of 3.4 eV and an advantageous band alignment with silicon, could be applied as a transparent electron-selective layer. Here, we report on SHJ solar cells utilizing PECVD GaN layers grown at 200°C as electron-selective contact. First devices exhibited open-circuit voltages of ~575 mV due to poor passivation, and low conductivity of the as-yet undoped GaN layers induced high series resistance (Rs). However, this Voc suggests the potential for electron selectivity if appropriate passivation and doping strategies are implemented.

Published in:
Proceedings of the 46th IEEE Photovoltaic Specialists Conference
Presented at:
46th IEEE Photovoltaic Specialists Conference, Chicago, Illinois, USA, June 16-21, 2019

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 Record created 2019-07-03, last modified 2020-04-20

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