New high efficiency photovoltaic technologies, such as silicon heterojunction (SHJ) solar cells and perovskite-on-silicon tandem solar cells, have set critical requirements for the design of their transparent electrodes, mainly new transparent conductive oxides (TCOs) simultaneously featuring high lateral conductivity and exceptionally low optical absorption over a broad spectral region (UV-IR).

New high efficiency photovoltaic technologies, such as silicon heterojunction (SHJ) solar cells and perovskite-on-silicon tandem solar cells, have set critical requirements for the design of their transparent electrodes, mainly new transparent conductive oxides (TCOs) simultaneously featuring high lateral conductivity and exceptionally low optical absorption over a broad spectral region (UV-IR). In addition to this, electrically and chemically well-‘matched’ interfaces with the carrier-selective and metal contacts of the solar cells are as well required to enhance device efficiency. Degenerate high mobility TCOs are ideal to achieve high conductivity and broadband transparency, as well as to reduce the contact resistance in the device. In this talk we compare the latest developments in high-mobility TCOs, mainly hydrogenated indium-based TCOs (e.g. IO:H), Zr-doped indium oxide (IZrO) and indium zinc oxide (IZO) as alternatives to the widely used Sn-doped indium oxide (ITO). IO:H and IZrO present exceptionally high electron mobilities (> 100 cm2/Vs) achieved at low deposition temperatures (< 200 °C), wide band gap (between 3.5 and 3.8 eV) and low sub-bandgap absorption. We discuss how these properties are strongly liked to a low density of defects and high crystalline quality independent of the growth substrate. The fundamental properties of these high-mobility TCOs, to their integration into high-efficiency SHJ cells as their front electrode and into semitransparent perovskites for tandem cells, will be furthermore discussed. Finally, we present recent efforts to replace or reduce indium in TCOs, discuss future challenges in the field of transparent electrodes for photovoltaics combining carrier selectivity, transparency and conductivity, and propose guidelines to design new TCOs with decoupled optical and electrical properties.