Engineering of Thin-Film Silicon Materials for High Efficiency Crystalline Silicon Solar Cells

Thin-film silicon layers deposited in parallel-plate PECVD reactors can be produced with varying microstructure, composition and properties, depending on deposition process conditions and on the underlying substrate properties. This allows for designing selective contacts well suited to limit recombination losses in wafer-based crystalline silicon solar cells. For such heterojunction selective contacts, we demonstrate that an hydrogenated amorphous silicon passivation layer with a high microstructure factor yields enhanced passivation, demonstrating > 30 ms carrier lifetime on 270 $\mu$m Fz wafer. Combining the developed intrinsic material together with doped layers with appropriate activation energy and defect density, we show silicon heterojunction solar cells with fill factor > 82 % and with certified efficiency up to 23.88 %. In addition, we report on PECVD process conditions impact on the functionality of back-contacted silicon heterojunction solar cells based on the innovative “tunnel-IBC” approach, which uses an advanced control and utilization of thin film silicon specific properties. A certified 24.42 % tunnel-IBC solar cell is reported, demonstrating the potential of this simple manufacturing approach for back-contacted devices. Advanced processing of thin film silicon layers is therefore demonstrated to enable for achieving high efficiency crystalline silicon devices.