High-efficiency Multicrystalline Silicon Solar Cells using Standard High-temperature, Float-zoned Cell Processing

Abstract

This paper reports recent results of fabricating multicrystalline silicon solar cells with the standard PERL (passivated emitter, rear locally‐diffused) cell high‐temperature processing sequence originally developed for float‐zoned wafers. One of these multicrystalline silicon cells with a planar front surface demonstrated a 645‐mV open‐circuit voltage and 18.2% energy conversion efficiency tested at the National Renewable Energy Laboratory and Sandia National Laboratories under the 100 mW cm−2 AM1.5 global spectrum at 25°C. This is the highest confirmed voltage and one of the highest confirmed conversion efficiencies ever reported to date for a multicrystalline silicon cell. Further optimization of the standard PERL processing and texturing of the cell surfaces is expected to improve the cell efficiency to over 19% in the near future. © 1997 John Wiley & Sons, Ltd.

Recent Developments in High-Efficiency PV Cells

“…Further improvement in cell efficiency to 18.6% has been achieved by decreasing the rear surface recombination velocity to 2 x 10 3 cm/s with deeper Al alloys (Rohatgi et al, 1996b). Subsequently, the UNSW group has achieved 18.2% efficiency in a MC-Si grown by the heat exchange method (HEM) by using their standard PERL process with processing temperatures exceeding 1050°C (Zhao et al, 1997).…”

Recombination and trapping in multicrystalline silicon

“…It has recently been realised that the lifetime of mc-Si can be nearly as high as that of single crystal silicon [3,4], that high temperature processing is not necessarily harmful to mc-Si [5,6], that the surfaces can be well passivated [7] and that high efficiency solar cell designs can be implemented in mc-Si wafers [5]. These advancements have led to conversion efficiencies over 18% [5,6,8] and open-circuit voltages over 650 mV [9]; the 20% efficiency mark has practically been reached [10]. Nevertheless, besides prime quality material and ultimate performance, research should be directed towards a better understanding of the mid and low quality mc-Si commonly used for mass production of solar cells.…”