Effect of thermally annealed atomic-layer-deposited AlOx/chemical tunnel oxide stack layer at the PEDOT:PSS/n-type Si interface to improve its junction quality

We investigated the effects of thermal annealing on an atomic layer deposition-fabricated AlOx/chemical tunnel oxide (ch-SiOx) stack layer, for passivating and enhancing the field-inversion at the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/n-type crystalline Si (n-Si) interface. Annealing in N2/H2 forming gas at 560 °C for 30 min increased the effective minority carrier lifetime (τeff) of the AlOx/ch-SiOx stack layer to 300–331 μs, which decreased sheet resistance and enhanced the built-in potential and open-circuit voltage in PEDOT:PSS/n-Si heterojunction solar cells to 750 mV and 645 mV, respectively. These improvements originate from the local chemical bond configuration of the tunnel oxide ch-SiOx, which determines the passivation ability and band alignment at the AlOx/n-Si interface.