| Summary: | 碩士 === 國立中興大學 === 光電工程研究所 === 105 === Passivated Emitter and Rear Cell (PERC) is the main structure of silicon solar cells. The open-circuit voltage and short-circuit current density of the cell were improved dramatically according to the good passivation on the surface. With this structure as a benchmark to derive into bifacial PERC solar cells, the benefit is just not only reduction of electrode paste but also efficiency gain from the rear side so that there is considerable potential in the market. In this study, we focus on the investigation of process adjustment and surface improvement for p-type bifacial PERC.
This thesis were divided into three sections:
1.The passivation on the rear surface has a significant improvement for PERC solar cells. Aluminum oxide (Al2O3) was generally deposited as passivated film by using atomic layer deposition (ALD) and we try to use higher negative charge density material hafnium oxide (HfO2) to comparison of the passivation effect. Combining with the Al2O3 film to discuss influences for PERC solar cells with the single and double passivated layers, the results show that the passivation effect of HfO2 is worse than that of Al2O3;
2.Silicon nitride (SiNx) thin film plays as the protective layer for passivated effects and reflection layer on the rear surface of the solar cells. After the passivated condition was confirmed, we study the optical property of SiNx to enhance reflection and absorption for the PERC cells at long wavelength. The influence of the overall thickness with Al2O3 and SiNx for IV characteristics of the cell was analyzed, and the better process parameters were obtained;
3.The passivated effect on the surface could be destroyed by the fabrication steps of the solar cells. Therefore, we investigate the influence of each steps and change the process sequence to reduce the subsequent contamination in order to find the best process steps. Besides, the metallization was carried out additional copper plating and screen printing to observe the PERC efficiency;
The experimental results show that the passivated stack layers with 10 nm Al2O3 and 190 nm SiNx combined with improved process flow has the best performance for the bifacial PERC. It was concluded that the efficiency is ηfront = 20.7%、ηrear = 8.3%、Jsc = 39.1 mA/cm2、Voc = 661 mV、F.F. = 80.1%.
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