COMPUTER MODELING OF CURRENT MATCHING IN A-SI-H A-SI-H TANDEM SOLAR-CELLS ON TEXTURED TCO SUBSTRATES/

Computer modelling is used as a tool for optimising a-Si:H/a-Si:H tand em cells on textured substrate in order to achieve current matching be tween the top and bottom cell. To take light scattering at the texture d interfaces of the cell into account, we developed a multi-rough-inte rface optical model which was used for calculating the absorption prof iles in the tandem cells. In order to simulate multi-junction solar ce ll as a complete device we implemented a novel model for tunnel/recomb ination junction (TRJ), which combines the trap-assisted tunnelling an d enhanced carrier transport in the high-held region of the TRJ.We inv estigated the influence of light scattering and thickness of the intri nsic layer of the bottom cell on the optimal ratio i2/i1 between the t hicknesses of the bottom (i2) and top (ii) intrinsic layers in the cur rent-matched cell. The simulation results show that increasing amount of scattering at the textured interfaces leads to a lower ratio i2/i1 in the current-matched cell. This ratio depends on the thickness of th e intrinsic layer of the bottom cell. The simulation results demonstra te that a-Si:H/a-Si:H tandem cell With 300 nm thick intrinsic layer in the bottom cell exhibits higher efficiency than the cell with 500 nm thick bottom intrinsic layer.