Industrially feasible casting-mono crystalline solar cells with PECVD AlOx/SiNx rear passivation stack towards 19.6% efficiency

Cost reduction and efficiency gain are the major goals of research and development in crystalline silicon solar cell technology. Casting-mono crystalline silicon produces higher cell efficiencies compared to multi-crystalline silicon material with the same average minority carrier lifetime and with a similarly low production cost. Aluminum oxide provides excellent passivation on crystalline solar cell and has received great research interests in recent years due to combination of chemical passivation and field-effect passivation provided by a large amount of fixed negative charges. In particular, deposition of AlOx using ALD or PECVD in PERC structure has been well studied. PECVD is preferred for its fast deposition rate. Our research shows that PECVD AlOx films indeed show good passivation quality on casting-mono wafers, which can achieve more than 200µs average lifetime, 700mV implied Voc and with good stability. Combined with the laser ablation to realize the PERC structure, the PECVD-AlOx contributes to a 12mV increase in Voc compared to the Al-BSF cell. The final cell efficiency reached 19.4% in average with a batch size of 30 wafers and 19.6% for the best cell. Additionally, PECVD AlOx can be easily integrated with the current industrial production line at no significant additional cost.