Exploring the Potential of Silicon Clathrate Films with NiOx‐Based Selective Contacts for Optoelectronic Devices

Abstract Silicon clathrates are a unique class of materials with a cage‐like structure that offer significant advantages for optoelectronic applications, particularly in indoor photovoltaics (IPV). Their direct bandgaps and tunable electronic properties from metal‐like to semiconductor‐like behavior enable a wide range of optoelectronic functionalities. In this study, a photovoltaic device is demonstrated based on semiconducting silicon clathrate films (SCF) synthesized from crystalline silicon (c‐Si) wafers, with NiOx incorporated as hole selective contact. XPS and Auger spectroscopy confirmed the incorporation of Na within the SCF framework, in agreement with the type‐II clathrate structure revealed by XRD analysis. Optical and electronic measurements indicate that the SCF exhibits intrinsic‐like behavior with a bandgap of 1.72 eV. Integration of SCF with NiOx resulted in rectification and a clear photovoltaic response under illumination, confirming device functionality. Band alignment analysis suggested efficient hole transport and secondary charge generation from the c‐Si substrate. These results highlight the importance of selective contact engineering for efficient charge extraction and demonstrate the potential for further optimization of SCF photovoltaic devices.