RTP process effect on multicrystalline mc-Si wafers and its impact on solar cell efficiency

Abstract

In this study, multicrystalline mc-Si wafers were subjected to a rapid thermal processing (RTP) cycle at a peak temperature of 620°C. Two wafers were passivated by silicon nitride (SiNx:H) layers, deposited by a PECVD system. A first wafer was protected (PW) from the direct radiative heating of the RTP furnace by placing the wafer between two as-cut mc-Si shield wafers during the heat treatment. A second one was not protected (NPW) and followed the same RTP cycle. Moreover, charges carrier lifetime was measured by the quasi-steady-state photoconductance (QSSPC) method before and after RTP process, an enhancement in the electrical proprieties was detected for the PW wafer. Further, wafers surface profiling by interferometer microscope show a morphological degradation of the NPW wafer compared to the protected one. Furthermore, solar cells with aluminum oxide (AlO x ) passivated rear side (Al-BSF) were elaborated using as substrates the treated mc-Si wafers. The electrical characteristics of the solar cells were determined by a sun simulator, before and after an illumination step by exposing the simples to 500W halogen lamps for 5h duration in work condition temperature of 60°C ±5°C. It was observed that the solar cell based on the PW protected wafer has indicated a good electrical stabilization and a weak efficiency degradation after the illumination step. Finally, the proposed method can lead to improving solar cell efficiency by an adequate second RTP processing.