Rapid processing of low-cost, high-efficiency silicon solar cells

Rapid and potentially low-cost processing techniques are analyzed and appli ed toward the fabrication of high-efficiency Si solar cells. (i) A technolo gy that can simultaneously form the phosphorus emitter, boron BSF, and ill situ oxide in a single high-temperature furnace step or: simultaneously dif fused, textured, and AR coated process (STAR) is presented. (ii) A high qua lity screen-printed (SP) contact methodology is developed that results in f ill factors of 0.785-0.790 on monocrystalline Si. (iii) Aluminum back surfa ce field (Al-BSF) formation is studied in detail to establish the process c onditions that result in optimal BSF action. (iv) Screen-printing of Al con ductor paste and rapid thermal processing (RTP) are integrated into the BSF procedure, and effective recombination velocities (S-eff) as low as 200 cm /s are demonstrated on 2.3 Omega-cm Si with this rapid thermal processing o f screen-printed contacts, Al alloyed BSP processes. (v) A novel passivatio n scheme consisting of a dielectric stack (plasma silicon nitride on top of a rapid thermal oxide) is developed to reduce the surface recombination ve locity (S) to approximate to 10 cm/s at the 1.3 Omega-cm Si surface. The im portant feature of this stack passivation scheme is its ability to withstan d a high-temperature anneal (700-850 degrees C) without degradation in surf ace recombination velocity. This feature is critical for most current comme rcial processes that utilize SP contact firing. (vi) Finally, the individua l processes are integrated to form high-efficiency, manufacturable devices. Solar cell efficiencies of 17% and >19% are achieved on FZ Si with SP and evaporated (photolithography) contacts, respectively.