A series resistance induced by cell interconnections will lead to a worse TCPMPP of solar modules compared with cells.

Atomic layer deposition (ALD) of thin Al 2 O 3 (≤10 nm) films is used to improve the rear surface passivation of large-area screen-printed p-type Si passivated emitter and rear cells (PERC). A blister-free stack of Al 2 O 3 /SiO x /SiN x is developed, leading to an improved back reflection and a rear recombination current (J 0,rear ) of 92 AE 6 fA/cm 2 . The Al 2 O 3 /SiO x /SiN x stack is blister-free if a 700 C anneal in N 2 is performed after the Al 2 O 3 deposition and prior to the SiO x /SiN x capping. A clear relationship between blistering density and lower open-circuit voltage (V OC ) due to increased rear contacting area is shown. In case of the blister-free Al 2 O 3 /SiO x /SiN x rear surface passivation stack, an average cell efficiency of 19.0% is reached and independently confirmed by FhG-ISE CalLab. Compared with SiO x /SiN x -passivated PERC, there is an obvious gain in V OC and short-circuit current (J SC ) of 5 mV and 0.2 mA/cm 2 , respectively, thanks to improved rear surface passivation and rear internal reflection.

In this paper, we evaluate p-type passivated emitter and rear locally diffused (p-PERL) and n-type passivated emitter and rear totally diffused (n-PERT) large area silicon solar cells featuring nickel/copper/silver (Ni/Cu/Ag) plated front side contacts. By using front emitter p-PERL and rear emitter n-PERT, both cell structures can be produced with only a few adaptations in the entire process sequence because both feature the same front side design: homogeneous n + diffused region with low surface concentration, SiO 2 /SiN x :H passivation, Ni/Cu/Ag plated contacts. Energy conversion efficiencies up to 20.5% (externally confirmed at FhG-ISE Callab) are presented for both cell structures on large area cells together with power-loss analysis and potential efficiency improvements based on PC1D simulations. We demonstrate that the use of a rear emitter n-PERT cell design with Ni/Cu/Ag plated front side contacts enables to reach open-circuit voltage values up to 676 mV on 1-2 Ω cm n-type CZ Si. We show that rear emitter n-PERT cells present the potential for energy conversion efficiencies above 21.5% together with a strong tolerance to wafer thickness and bulk resistivity.

No abstract

We present large-area n-type PERT solar cells featuring a rear boron emitter passivated by a stack of ALD Al 2 O 3 and PECVD SiO x . After illustrating the technological and fundamental advantages of such a device architecture, we show that the Al 2 O 3 /SiO x stack employed to passivate the boron emitter is unaffected by the rear metallization processes and can suppress the Shockley-Read-Hall surface recombination current to values below 2 fA/cm 2 , provided that the Al 2 O 3 thickness is larger than 7 nm. Efficiencies of 21.5% on 156-mm commercial-grade Cz-Si substrates are demonstrated in this study, when the rear Al 2 O 3 /SiO x passivation is applied in combination with a homogeneous front-surface field (FSF). The passivation stack developed herein can sustain cell efficiencies in excess of 22% and V o c above 685 mV when a selective FSF is implemented, despite the absence of passivated contacts. Finally, we demonstrate that such cells do not suffer from light-induced degradation.