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c-Si Wafers (c-si + wafer)
Selected AbstractsRole of a-Si:H bulk in surface passivation of c-Si wafersPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010A. Illiberi Abstract The low thermal stability of hydrogenated amorphous silicon (a-Si:H) thin films limits their widespread use for surface passivation of c-Si wafers on the rear side of solar cells. We show that the thermal stability of a-Si:H surface passivation is increased significantly by a hydrogen rich a-Si:H bulk, which acts as a hydrogen reservoir for the a-Si:H/c-Si interface. Based on this mechanism, an excellent lifetime of 5.1 ms (at injection level of 1015 cm,3) is achieved after annealing at 450 °C for 10 min. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Passivation study of the amorphous,crystalline silicon interface formed using DC saddle-field glow dischargePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010Barzin Bahardoust Abstract The DC saddle-field (DCSF) glow discharge method was used to deposit intrinsic a-Si:H onto c-Si to passivate the c-Si surface. The effective minority carrier lifetime in the heterostructures as a function of the excess minority carrier density in the c-Si wafers was measured. The results were then analyzed in the context of recombination associated with interface defect states using three known recombination models. The defect density and the charge density at the interface are inferred. In addition subsequent annealing of the samples was studied. It is shown that for our intrinsic a-Si:H samples improvements in surface passivation are directly correlated with the reduction of interface defects and not the reduction of minority carrier concentration at the interface due to electric field. We have achieved excellent surface passivation with effective carrier lifetime >4,ms for an intrinsic a-Si:H sample deposited at a process temperature of 200,°C and thickness of about 30,nm. It is also demonstrated that subsequent annealing, at 240,°C, of the samples which were prepared at process temperatures <240,°C greatly increases the effective lifetime. [source] Plasmas for texturing, cleaning, and deposition: towards a one pump down process for heterojunction solar cellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Mario Moreno Abstract Low temperature plasma deposition of a-Si:H thin films has emerged as a promising alternative for high efficiency hetero junction (HJ) solar cells. In this work we study plasma processes for texturing and cleaning c-Si wafers pursuing a low cost dry fabrication process of HJ solar cells. We have studied two independent plasma processes: i) Texturing of c-Si wafers using SF6 - O2 plasmas in a RIE system, in order to reduce the surface reflectance and therefore improve the light trapping. The effects of the RF power and gas ratio on the c-Si surface texture have been studied in detail. Highly textured surfaces, with very low reflectance values (around 6% in the range of 300 , 1000 nm) have been achieved. ii) Etching of the native oxide and passivation of the c-Si surface by plasma, in a standard RF PECVD system. We used SiF4 plasma with optimized conditions for an efficient native oxide removal, and without breaking the vacuum, 40 nm of a-Si:H were deposited in order to passivate the c-Si surface. High effective lifetime values were obtained (,eff , 1.5 ms), providing high implicit open circuit voltages (Voc , 0.713 V) and low surface recombination velocities (Seff < 9 cm s -1). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||