Amorphous Silicon / Crystalline Silicon Heterojunction Solar Cells

Abstract

The basic structure and the operation of heterojunction solar cells are given. Their economic potential is discussed. The historic development of a-Si:H/c-Si heterojunction solar cells is briefly sketched. The constituting materials and the band diagrams are described. The individual process steps such as polishing, etching, texturing, i-layer, BSF, ARC, and metal deposition are explained. Cell concepts are demonstrated. Problems and challenges are choice of the base material, n/p versus p/n, surface states, optimized passivation, emitter, and BSF layers. As to the measurement techniques, examples are presented such as absorption, reflection, transmission, microwave techniques, photo- and electroluminescence, ellipsometry, Raman spectroscopy, dark and light IV, spectral response, REM, and LBIC. The simulation is based on the AFORS-HET code, and its results are compared to experiments. Long-term stability and radiation hardness are measured. The efficiency results of various laboratories are listed.