Selective Transparent Contacts Based on a Hafnium‐Titanium Oxide Alloy with Optimized Band Alignment for c‐Si Solar Cells

Abstract In this study, the potential of hafnium‐titanium oxide (Hf_xTi_1‐xO_y, HTO) thin films is explored and deposited by low‐temperature (75 °C) atomic layer deposition (ALD) as selective contacts for crystalline silicon (c‐Si) solar cells. Through a comprehensive analysis of their selectivity, optical and chemical properties, and band alignment characteristics, the HTO films are shown to exhibit remarkable electron selectivity. They formed efficient ohmic contacts on n‐type silicon, while exhibiting diode‐like characteristics on p‐type silicon, confirming their selective behavior. Band alignment analysis at the HTO/n‐Si interface revealed a high valence band offset and a low conduction band offset, facilitating efficient electron extraction and blocking hole transport. Optical measurements demonstrate the high optical transparency of the HTO films with a bandgap above 3.5 eV, making them suitable for photovoltaic applications. A proof‐of‐concept photovoltaic device is evaluated, and significant improvements are observed in all solar cell parameters following the incorporation of HTO, highlighting the potential of low‐temperature ALD‐deposited HTO films as efficient electron‐selective contacts for next‐generation c‐Si solar cells.