Rear Junction Bifacial Screen-Printed Double Side Passivated Contact Si Solar Cells

We report on the fabrication of fully screen-printed bifacial large area (244
$\mathbf{cm}^{\boldsymbol{2}})\boldsymbol{\sim 20.6\%}$
efficient rear junction cells with full area poly-Si/SiOx passivating contacts on both sides. A full area thin n-TOPCon (~35 nm) was deposited on the textured front side in conjunction with thick p-TOPCon (~250 nm) on the planar rear side using LPCVD grown intrinsic poly-Si and ex-situ doping technology. Excellent
$\mathbf{iV}_{\mathbf{o}\mathbf{c}}$
of ~730 mV was achieved on the cell precursor after SiNx capping layers on both sides, prior to metallization. However, iVoc dropped from 730 to 715 mV after a simulated high-temperature firing process
$(\boldsymbol{ > 700 \ ^{\circ}} \mathbf{C})$
without metallization. This was mainly due to the degradation of textured n-TOPCon passivation quality after the firing cycle without the metal paste. After fire through screen-printed contact formation, a preliminary efficiency of -20.6% was achieved with full area double side TOPCon (DS-TOPCon) cell structure with a high Voc of -700mV and excellent contact resistance. Device modelling shows that further optimization of paste and firing can lead to much higher efficiency.