Solar Cells on Multicrystalline Silicon Thin Films Converted from Low-Cost Soda-Lime Glass

Abstract

Fabrication and characterization of solar cells based on multicrystalline silicon (mc-Si) thin films are described and synthesized from low-cost soda-lime glass (SLG). The aluminothermic redox reaction of the silicon oxide in SLG during low-temperature annealing at 600 – 650 °C leads to an mc-Si thin film with large grains of lateral dimensions in the millimeter range, and moderate p-type conductivity with an average Al acceptor concentration between 5 × 10¹⁶ and 1.2 × 10¹⁷ cm⁻³ in the bulk. A residual composite layer of mainly alumina and unreacted Al forms beneath the mc-Si thin film as the second product of the crystalline silicon synthesis (CSS) process, which can be used as rear contact in a vertical solar cell design. The mc-Si absorber (≈10 µm) is thin enough that the diffusion length given by a minority carrier lifetime of ≈1 µs exceeds the path length to the top contact several times. Homojunction and heterojunction diodes have been fabricated on the mc-Si thin films and show great potential of CSS for the realization of high-performance solar cells.