Single nanowire solar cells beyond the Shockley-Queisser limit

TL;DR

This study demonstrates that single GaAs nanowire solar cells can surpass the Shockley-Queisser limit by utilizing their light concentrating properties, achieving significantly higher photocurrent than traditional models predict.

Contribution

The paper reveals how nanowire geometry enhances light absorption and photocurrent, pushing efficiency beyond conventional theoretical limits for III-V solar cells.

Findings

Photocurrent exceeds Lambert-Beer law predictions by over an order of magnitude.

Standing nanowire acts as a light concentrator, increasing absorption.

Potential for higher efficiency limits in nanowire-based photovoltaic devices.

Abstract

Light management is of great importance to photovoltaic cells, as it determines the fraction of incident light entering the device. An optimal pn-junction combined with an optimal light absorption can lead to a solar cell efficiency above the Shockley-Queisser limit. Here, we show how this is possible by studying photocurrent generation for a single core-shell p-i-n junction GaAs nanowire solar cell grown on a silicon substrate. At one sun illumination a short circuit current of 180 mA/cm^2 is obtained, which is more than one order of magnitude higher than what would be predicted from Lambert-Beer law. The enhanced light absorption is shown to be due to a light concentrating property of the standing nanowire as shown by photocurrent maps of the device. The results imply new limits for the maximum efficiency obtainable with III-V based nanowire solar cells under one sun illumination.