Theoretical studies of silicon hetero-junction solar cells with rib structure

Yukimi Ichikawa,Makoto Konagai,Yoshiaki Osawa,Hiroshi Noge

doi:10.1063/1.5098964

Abstract

The open-circuit voltage of a solar cell is known to increase with deceasing wafer thickness if the cell is adequately passivated. However, it is not easy to handle very thin wafers because they are brittle and are subject to warpage. To provide thinned wafers that have adequate mechanical strength, we proposed a thin Si wafer-based solar cell that uses a rib structure in a previous work. We formed a lattice-shaped rib structure on the rear side of a thin Si wafer to improve the wafer’s strength and fabricated the conventional Si hetero-junction structure by depositing hydrogenated amorphous Si on the wafer. For optimum design of the rib structure cell, we analytically studied the effect of rib dimensions on wafer strength and photovoltaic characteristics. A simplified structural analysis was performed to investigate the mechanical strength of the rib structure for various rib dimensions. Photovoltaic characteristics of rib structure silicon hetero-junction cells were also studied by a two-dimensional device simulator to understand the effect of rib dimensions. From these analyses, we theoretically demonstrated that the rib structure cell is a very good candidate to realize thin wafer Si solar cell, and can achieve both mechanical strength and electrical performance of thin Si solar cells.

Highlights

The energy conversion efficiency of single crystalline silicon solar cells has improved steadily over the last three decades and recently exceeded 26%.1 To further improve the efficiency, the wafer thickness remains an important factor
There is an optimum wafer thickness that leads to high cell conversion efficiency; favorable wafer thickness is considered to be 100 μm or less
We studied the effect of the rib dimension on the photovoltaic performances using this model

Summary

INTRODUCTION

The energy conversion efficiency of single crystalline silicon solar cells has improved steadily over the last three decades and recently exceeded 26%.1 To further improve the efficiency, the wafer thickness remains an important factor. The short-circuit current density (JSC) reduces for thinner solar cells This reduction is, prevented using optical confinement with textured structures.. There is an optimum wafer thickness that leads to high cell conversion efficiency; favorable wafer thickness is considered to be 100 μm or less.. There is an optimum wafer thickness that leads to high cell conversion efficiency; favorable wafer thickness is considered to be 100 μm or less.5 It is, very difficult to handle such thin wafers during the cell fabrication processes, and the production yield can be very low because of wafer breakage. Very difficult to handle such thin wafers during the cell fabrication processes, and the production yield can be very low because of wafer breakage To overcome these difficulties, we have developed thin silicon solar cells that use a rib structure.. We carried out analytical studies to clarify the rib size effect, and the details are reported here

STRUCTURAL ANALYSES FOR RIB WAFERS

DEVICE SIMULATION FOR RIB STRUCTURE CELLS

CONCLUSIONS