High Efficient, Cost-Effective, and Reliable Silicon Solar Cells and Modules in Mass Production

Abstract

Over the last decade, significant improvements in cost reduction as well as in conversion efficiency increase were achieved in large-scale industrial production, making PV cost competitive with other means of electricity generation. In many regions worldwide, PV achieves the lowest levelized cost of electricity. Several different factors made this tremendous achievement possible-namely economy of scale, a lean and efficient production process, and high conversion efficiencies. In this work, some of the key concepts and methods are described based on Hanwha Q CELLS’ experience. The methods and approaches for the fast transfer of cell technologies from laboratory to production and for accelerated progress in cell efficiency, quality, and reliability of the cell and module product are described. Over the last decade, the cell conversion efficiency increased by 0.5%abs per year. Currently, average cell conversion efficiencies exceeding 20% using boron-doped p-type multicrystalline (mc-Si) and 22%, using Czochralski-grown silicon (Cz-Si) substrates, are achieved on a multi-GW scale. Currently (as of Jan 2018) produced Q.ANTUM solar modules from these cells exhibit output powers of 325 Wp based on 120 half Cz cells and of 350 Wp based on 72 full multicrystalline cells. Besides just the performance, it is critical to investigate the reliability of solar modules based on p-type solar cells with dielectrically passivated rear. In terms of reliability, light-induced degradation (LID) is examined in detail, with conditions relevant for the activation of both the boron–oxygen (BO) defect, and “Light and Elevated Temperature Induced Degradation” (LeTID). While the formation of the BO defect has been considered the most prominent LID mechanism in boron-doped p-type Cz-Si, recently it was shown that LeTID is another important issue for passivated emitter and rear cells (PERC) on both mc-Si and Cz substrates. When not adequately suppressed, LeTID can occur on p-type PERC with degradation in output power of >6%; critically, it cannot be suppressed in a straightforward manner by conventional processing steps used to permanently deactivate the BO defect. In contrast to conventional PERC, Hanwha Q CELLS’ Q.ANTUM technology is shown to reliably suppress both LID due to BO defect formation and LeTID, for both p-type mc-Si and Cz-Si substrates.