High-Efficiency Industrial-Type PERC Solar Cells Applying ICP AlOx as Rear Passivation Layer

Abstract

Passivated emitter and rear cells (PERC) are considered to be the next generation of industrial-type screen-printed silicon solar cells. However, today there exist only few deposition methods for rear passivation layers which meet both, the high-throughput and low-cost requirements of the PV industry in combination with high-quality surface passivation properties. In this paper, we evaluate and optimize a novel deposition technique for AlO x passivation layers applying an inductively coupled plasma (ICP) plasma-enhanced chemical vapour deposition (PECVD) process. The ICP AlOx deposition process enables high deposition rates of up to 5 nm/s as well as excellent surface recombination velocities below 10 cm/s after firing. When applied to PERC solar cells the ICP AlOx layer is capped with a PECVD SiNy layer. We achieve independently confirmed conversion efficiencies of up to 20.1% for large-area (15.6x15.6 cm 2 ) PERC solar cells processed at ISFH with screen-printed metal contacts and ICP AlOx/SiNy rear side passivation on standard boron-doped Czochralski-grown silicon wafers. The internal quantum efficiency reveals an effective rear surface recombination velocity Srear of (90 ± 30) cm/s and an internal rear reflectance Rb of (91 ± 1)% which demonstrates the excellent rear surface passivation of the ICP AlOx/SiNy layer stack. PERC solar cells processed in the Q-Cells Research Line achieve efficiencies up to 19.6% with ICP AlOx/SiNy rear passivation which is comparable to the reference process at Q-Cells.