‘SolarEYE’ loss analysis of screen-printed, n-type silicon solar cells with ‘monoPoly’ PECVD rear passivated contacts

Abstract

We present cell results and loss analysis summaries for screen printed, five-busbar (5BB), M2-size, n-type silicon solar cells made with rear-passivated contacts deposited with PECVD (referred to as ‘n-monoPoly’ cells). The PECVD process avoids the need to mask the front during the formation of the rear passivated contact. A median open circuit voltage (VOC) of 702 mV and a peak cell VOC of 705 mV was demonstrated. Improvements to the passivated contact stack led to a passivated rear surface recombination current density (J0-poly) of 5 fA/cm2 and an area-normalised rear metal recombination current density (J0-met) of 3 fA/cm2 for fire-through contacts. The cell models extracted from SolarEYE loss analysis were used to identify the largest VOC and FF losses. The best-fit cell model for 5BB n-monoPoly cells was used to: (i) project realistic 12 busbar (12BB) cell efficiencies; and (ii) simulate the output of the devices under bifacial operation. This 12BB n-monoPoly cell structure with a uniformly-doped p+ emitter has a median efficiency potential of 23.6%, and a potential bifacial output of 7 W with a rear irradiance factor of 0.3 – this would translate to an output of 12.5 W for M12-size wafers with the same rear irradiance. If a selectively-deposited passivated contact is added on the front, the median batch efficiency and VOC of screen-printed n-monoPoly cells can reach 24.7% and 720 mV for these 12BB devices.