Effective role of the SnO₂ cap layer thickness in improving the structural morphology, optical properties and enhancing the photovoltaic performance of fabricated n-SnO₂/n-CdS/p-Si solar cells

In the current framework, the n-SnO₂/n-CdS/p-Si heterostructure was fabricated at different tin dioxide (SnO₂) thicknesses (d = 30, 60, 90, 120, 150, and 180 nm). In this device, nickel (Ni) and platinum (Pt) strips were used as back and front contact electrodes, respectively. The structural and optical properties of the SnO₂ cap layers were studied. Using a frequency of 10 MHz, a typical dark capacitance–voltage (C–V) characteristic of the fabticated heterostructure was measured to determine the electronic parameters. In order to understand the behavior of the fabricated device under dark conditions, the current density–voltage (J–V) characteristics were analyzed. The measurements showed a significant rectifying behavior, demonstrating the junction’s good rectification characteristic. The devices’ performance parameters, including open-circuit voltage (V_oc), short-circuit current density (JSC), fill factor (FF), and power conversion efficiency (PCE), were all discovered to be affected by the cap layer’s thickness when subjected to AM1.5 illumination. In this study, the higher thickness window layer had a power conversion efficiency of 14.25%. Remarkably, the addition of a cadmium sulfide buffer layer, and changing the thickness of the SnO₂ cap layer were critical in improving the photovoltaic properties, with the suitability of the last SnO₂ cap layer confirmed due to its good structural, optical, quantum efficiency \(\eta\), spectral photoresponsivity \(\Re\) and photovoltaic properties.