Emitter Profile Tailoring to Contact Homogeneous High Sheet Resistance Emitter

• Published in: Energy procedia 2012, Vol.27, p.432-437
• Main Authors: Safiei, A., Windgassen, H., Wolter, K., Kurz, H.
• Format: Article
• Language: English
• Subjects: Emitter formation; high sheet resistance emitter; laser processing; selective emitter
• ISSN: 1876-6102; 1876-6102
• DOI: 10.1016/j.egypro.2012.07.089

In this work we report on successful direct contacting of high sheet resistance (RSH) emitter at 100Ω/sq by emitter profile manipulation. The formation of lightly doped emitter via POCl3 diffusion was investigated and optimized by the variation of temperature, time and gas fluxes. Sheet resistance mapping and emitter profile analysis have been done by four-point-probe and Electrochemical Capacitance Voltage (ECV) measurements. By increasing the depth of the n++ layer and at the same time reducing the peak concentration of inactive phosphorous doping, an efficiency gain of up to 0.7% absolute was achieved for multicrystalline silicon (mc-Si) solar cells. Suns-VOC measurements show an even higher gain of up to 1% absolute. In this work five different silver pastes are analysed accompanied by three different simulated grid designs. Electroluminescence imaging technique was used to characterize the spatially-resolved electrical properties of the solar cells. Based on these investigations we evaluated a 160Ω/sq emitter and could demonstrate by laser doping that the minimum n++ layer depth for high fill factors is approx. 25nm leading to 0.4%abs efficiency gain.