The influence of porous silicon on junction formation in silicon solar cells

In this work the results of a structural investigation by SEM of porous silicon (PS) before and after diffusion processes are reported. The formation of PS n⁺/p structures were carried out on PS p/p silicon wafers with two methods: from POCl₃ in a conventional furnace and from a phosphorous doped paste in an infrared furnace. Sheet resistance was found to be a strong function of PS structure. Further details on sheet resistance distribution are reported. The electrical contacts in prepared solar cells were obtained by screen printing process, with a Du Ponte photovoltaic silver paste for front contacts and home-prepared silver with 3% aluminium paste for the back ones. Metallization was done in the infrared furnace. Solar cell current–voltage characteristics were measured under an AM 1.5 global spectrum sun simulator. The average results for multi-crystalline silicon solar cells without antireflection coating are: I_sc=720 (mA), V_oc=560 (mV), FF=69%, Eff=10.6% (area 25 cm²).