COMPREHENSIVE STUDY OF SINGLE AMORPHOUS AND TANDEM MICROMORPH SOLAR CELLS AND MODULES ON FLEXIBLE ALUMINUM SUPERSTRATE PREPARED IN ROLL-TO-ROLL PROCESS

摘要

Thin film silicon technology is one of the most promising branches of the growing photovoltaic industry. For its lower cost, roll-to-roll deposition process on sacrificial Al superstrate is being tested for use in large industrial production at Helianthos bv. Fourier Transform Photocurrent Spectroscopy (FTPS) is a modern method widely used for thin film silicon solar cell diagnostics. At the same time the optical modeling of light management in thin film solar cells is a key tool for structure optimization. Here we refer to a comprehensive study of a single a-Si:H or tandem a-Si:H/μc-Si:H solar cell comprising material quality assessment by FTPS, optical constants evaluation by PDS (Photothermal Deflection Spectroscopy) and T/R spectroscopy, quantum efficiency measurements by FTPS and optical simulations by our numerical model Cell. This is not an easy task because the aluminum foil, that is later in the process etched off, complicates the FTPS and optical measurement. The result of our study is the assessment of optical parameters of all layers forming the cell and the calculation of limiting efficiencies for several proposed cell structures. For absorbers we can evaluate the electronic quality by the measurement of sub-bandgap absorption in a single solar cell and newly also in a tandem solar cell. We also refer to the possibility and to our experimental experience with such measurement performed on completed modules.