Designing band offset of a-SiO:H solar cells for very high open-circuit voltage (1.06 V) by adjusting band gap of p–i–n junction

TLDR: In this paper, a glass/tin oxide (SnO2)/hydrogenated amorphous silicon oxide (a-SiO:H) (p-i-n)/back electrode was used to match the world's highest open-circuit voltage (Voc: 1.06 V).

Abstract: We have matched the world’s highest open-circuit voltage (Voc: 1.06 V) achieved to date for a layered structure comprised of a glass/tin oxide (SnO2)/hydrogenated amorphous silicon oxide (a-SiO:H) (p–i–n)/back electrode. For the purposes of this study, we adjusted the band gaps of each layer (p–i–n) to improve overall film quality. Fine-tuning of band profiles with reference to activation energy and optical band gap allowed us to offset the conduction band and the valence band of each layer (p–i–n) and thus improve the built-in potential rather than the electron conductivity, Fourier transform infrared spectroscopy, transmittance or reflectance ratio, resulting in a high Voc. To fully exploit the characteristics of wide-band-gap materials and prevent problems with absorbance, we employed commercially available SnO2 in the front transparent conductive oxide instead of zinc oxide. Using our deposition and evaluation technologies to build a wide-band-gap single solar cell, we succeeded in matching the world’s highest Voc of 1.06 V (Eff: 5.38%, Jsc: 8.15 mA/cm2, FF: 0.624).