Interdigitated laser-contacted solar cell on liquid-phase crystallized silicon on glass

Abstract

10 µm thick liquid-phase crystallized silicon (Si) layers on 3.2 mm Borofloat 33 glass (5cm x 5cm) are fabricated by continuous wave line focus laser (808 nm). A sputtered SiO2/SiON layer stack has been implemented as barrier layer at the glass Si interface. Solar cells with interdigitated back contact are prepared on these multicrystalline layers by using low temperature (<400ºC) Doped-by-Laser (DopLa) fabrication concept. ALDAl2O3/ PECVD amorphous intrinsic Si carbide (SiCx(i)) stack for emitter passivation and a-SiCy(i)/P-doped a- SiCz(n)/a-SiCx(i) stack for base passivation are deposited. With short pulse (ns) UV laser (355 nm) p-type emitter (by Al-diffusion from Al2O3) and point contacts with back surface field (by P-diffusion from a-SiCz(n) layer) are fabricated on n-type mc-Si absorbers layers. Solar cell process steps are monitored by charge carrier lifetime measurements using the quasi steady-state photoconductance method. A strong dependency of charge carrier lifetime on injection level and doping density of absorbers is observed. Higher lifetimes are found for lower absorber doping concentrations. In 0.7 Ωcm LPCSG absorber highest τ eff ≈300 ns corresponding to L eff > 20 µm is found. Laserdoping and contacting using UV laser resulted in small (< 20 mV) loss of Voc(1sun). Crack formation in LPCSG absorbers after laser crystallization process presents technological problems in the preparation of the interdigitated metal contact.