Hierarchical Transparent Back Contacts for Bifacial CdTe PV

A hierarchical transparent back contact leveraging an AlGaO_<i>x</i> passivating layer, Ti₃C₂T_<i>x</i> MXene with a high work function, and a transparent cracked film lithography (CFL) templated nanogrid is demonstrated on copper-free cadmium telluride (CdTe) devices. AlGaO_<i>x</i> improves device open-circuit voltage but reduces the fill factor when using a CFL-templated metal contact. Including a Ti₃C₂T_<i>x</i> interlayer improves the fill factor, lowers detrimental Schottky barriers, and enables metallization with CFL by providing transverse conduction into the nanogrid. The bifacial performance of an AlGaO_<i>x</i>/Ti₃C₂T_<i>x</i>/CFL gold contact is evaluated, reaching 19.5% frontside efficiency and 2.8% backside efficiency under 1-sun illumination for a copper-free, group-V doped CdTe device. Under dual illumination, device power generation reached 200 W/m² with 0.1 sun backside illumination.