Cost-effective n-Pasha solar cells with efficiency above 20%

By Astrid Gutjahr, ECN Solar Energy; Delislava Saynova, ECN Solar Energy; Eric Kossen, ECN Solar Energy; John Anker, ECN Solar Energy; Ingrid Romijn, ECN Solar Energy; Kees Tool, ECN Solar Energy

This paper presents recent developments of ECN’s n-Pasha (passivated on all sides H-pattern) solar cell technology. The n-Pasha cell, currently being produced on an industrial scale by Yingli Solar, is a solar cell fabricated on n-type Cz material with homogeneous diffusions, dielectric passivation and printed metallization on both sides. The metallization is applied in an open H-pattern to both sides, which makes it suitable for bifacial applications. In order to improve both cell performance and the cost of ownership of n-Pasha solar cells, the ECN R&D team has focused on several aspects of the device design and processing. By reducing metal coverage and improving the quality of the front-side metallization, tuning the back-surface field (BSF) doping and improving the front- and rear-surface passivation, it has been possible to obtain an average efficiency of 20%, with top efficiencies of 20.2%. At the same time, the amount of silver used for metallization
has been decreased by over 50% and is now similar to that used for p-type solar cells. Furthermore, it is shown that with the ECN n-Pasha cell concept, wafers from the full resistivity range of n-Cz ingots can be used to make cells without losses in efficiency. Combining the improved efficiency and the reduction in cost makes the n-Pasha cell concept a very cost effective solution for manufacturing highly efficient solar cells and modules.