Investigation Of Thin Silicon Solar Cells And N-type Bifacial PERT Solar Cell With Ceramic Roller Inline Diffusion

Cost reduction and efficiency promotion are well-known development directions faced by photovoltaic industry.Currently,the highest conversion efficiency of crystalline silicon cell is 26.7%in the world.As for China,the highest efficiencies of 24.85%and 23.2%have been realized for mono-crystalline silicon（c-Si）and multi-crystalline silicon（mc-Si）solar cells,respectively.A bottleneck has been reached to further improve the efficiency of photovoltaic cells.Therefore,cost reduction have rised great concern for academic research in this filed.This thesis mainly focuses on some special processes of high-efficiency and low-cost crystalline silicon cells in three aspects.Firstly,thinning process of crystalline silicon wafers was investigated by means of acidic-solution etching and its mechanical,optical and electrical properties were explored.Secondly,thin mc-Si solar cells based on conventional industrial process were fabricated and studied.Thirdly,a novel diffusion process including ultrasonic atomization pre-deposition and furnace diffusion with ceramic roll were used to fabricate double-sided n-type Passivated Emitter and Rear Totally Diffusion（PERT）solar cells.An acidic solution was used to etch silicon wafer.Compared with normal 180μm-thick c-Si wafers,thin c-Si wafers show better mechanical properties.Due to the great optical loss in long-wavelength region of solar spectrum,it is necessary to apply a suitable textured surface structure to enhance light trapping for the thin Si solar cell.Meanwhile,a better surface passivation for is highly required to realize for the higher open circuit voltage of thin Si solar cell.120μm-thick p-type mc-Sisolar cells with full Al back surface filed（BSF）were fabricated based on conventional production line with the highest efficiency of 19.13%,which is comparable to that of 180μm-thick solar cells（19.21%）.120μm-thick mc-Si cells have greater mechanical strength with average bending displacement of 15.87 mm.This feather facilitates the development of advanced flexible solar modules.We first reported that thin mc-Si solar cells have less LID effect than 180μm-thick solar cells.This effect make our thin mc-Si cell has great potential for longt-term practical applications.In addition,a method to fabricated bifacial n-type PERTsolar cells was picked up.This thesis demonstrates an approach in which a pn junction and BSF were formed by using depositing liquid diffusion source at room temperature by ultrasonic atomization,followed by double-sided diffusion through ceramic roller inline diffusion furnace（CRID）.The sheet resistance of front emitter and back surface filed were regulated and controlled by optimizing atomization time,diffusion time and diffusion temperature.The optimal parameter window of60～78Ω/□and 22～33Ω/□were found for square resistances(R_sq)of emitter and BSF,respectively.Finally,the champion front-and rear-sided bifacial n-PERT solar cells have the efficiency of 18.02%and 13.55%,respectively,with a bifacial factor of 75.2%.