Performance improvements through gradient layers in transparent passivating contact solar cells

<h2>Summary</h2> Transparent passivating contact solar cells using hydrogenated n-type nanocrystalline silicon carbide (nc-SiC:H(n)) utilize a double-layer stack consisting of one passivation-optimized and one conduction-optimized nc-SiC:H(n) layer. This double-layer configuration limits the fill factor (<i>FF</i>) due to the passivating layer's low electrical conductivity. This study enhances this structure by introducing a gradient layer that transitions from passivating-like to conducting-like properties. While replacing the passivating layer alone does not improve performance, when combining it with an ultrathin passivating seed layer, the gradient layer effectively balances voltage and <i>FF</i> trade-offs. This results in higher device voltage and <i>FF</i>. Microstructural analysis shows hydrogen content near the crystalline Si interface similar to the double-layer approach but with increased electrical conductivity earlier in the layer stack. These improvements boost both <i>FF</i> and open-circuit voltage by 0.6% absolute and over 4 mV, respectively.