(Georgia Institute of Technology, 1998-07)
Moschner, J. D.; Doshi, P.; Ruby, D. S.; Lauinger, T.; Aberle, A. G.; Rohatgi, Ajeet
This work presents a comprehensive study on fast, low-cost methods for the electronic passivation of the phosphorus-diffused front surface and the non-diffused p-type rear surface of crystalline Si solar cells.
Titanium dioxide is compared with rapidly-grown thermal oxide (RTO) and PECVD silicon nitrides from three different laboratories. Double layers of RTO and Ti02 or SiN are also investigated. We demonstrate that SiN and RTO single layers can provide very good passivation on both the front and back surface of solar cells. It is also
shown that double layers consisting of a thin RTO film and silicon nitride can improve the passivation quality of
most SiN layers, and enhance the stability under thermal treatment. With the proper choice of RTO, SiN, and thermal treatment, excellent surface recombination velocities on the back as well as very low emitter saturation currents can he reached using these fast, industrially feasible methods. All films used also provide or are compatible with a good antireflection coating of the cell surface.
(Georgia Institute of Technology, 1998-07)
Meier, D. L.; Davis, H. P.; Shibata, A.; Abe, T.; Kinoshita, K.; Bishop, C.; Mahajan, S.; Rohatgi, Ajeet; Doshi, P.; Finnegan, M.
Contacts to <111> Si which are self-doping and self-aligning were investigated. Such contacts are applicable both to conventional cell structures as selective emitters and to more demanding structures such as
interdigitated back contact cells. Emphasis was placed on alloyed contacts of AI for providing a self-doping p-type
contact and of Ag-Sb for a self-doping n-type contact. Alloying at 900°C of 1.1% (wt.) Sb in Ag doped Si to a value of 2 x 10 (18) Sb/cm(3), suggesting a 5% (wt.) Sb is needed for ohmic contact. An AI alloy p-n junction was found to be suitable for a solar cell if placed at the back of the cell, with 13.2% efficiency and good IQE
demonstrated for a fully screen-printed dendritic web cell. A prototype interdigitated back contact cell was
fabricated by screen printing (AI and Ag) with tight alignment (100 11m lines and spaces) on a dendritic web substrate with an efficiency of 10.4%.