A-SiCx:H and A-SiOx:H Barrier Layers Embedded in the P/I and I/N Regions on the Performance of A-Si:H P-I-N Solar Cells

In this work, hydrogenated amorphous silicon carbide (a-SiCx​:H) and hydrogenated amorphous silicon oxide (a-SiOx​:H) films with similar optical bandgaps (Eg​), refractive indices (n), and extinction coefficients (k) were fabricated using pulse-wave modulation plasma technology by controlling the plasma turn-on and turn-off time ratio (ton​​/toff​). These films were placed at the 1/4 position of the p/i and i/n interfaces of hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells to investigate their influence on solar cell performance. Experimental results showed that when deviations in Eg​, n, and k were less than 0.2%, 1.4%, and 4.1%, respectively, placing a-SiCx​:H and a-SiOx​:H films at the p/i and i/n interfaces increased the open-circuit voltage (Voc​​) and decreased the short-circuit current due to valence band (ΔEv​) or conduction band (ΔEc​​) offsets. The reduction in cell fill factor (FF) and efficiency (η) caused by placing a-SiCx​:H and a-SiOx​:H films at the p/i interface was greater than that caused by placing them at the i/n interface. Placing the a-SiCx​:H film at the p/i interface significantly improved the Voc​​. Due to the n-type doping effect of oxygen atoms, the a-SiOx​:H film exhibited the lowest FF and η at the p/i interface; however, when placed at the i/n interface, it yielded FF and η values second only to the a-Si:H standard reference cell. Appropriately placing the a-SiCx​:H film at the p/i interface and the slightly n-type a-SiOx​:H film at the i/n interface can effectively improve the Voc​​, FF, and η of p-i-n solar cells.