Parasitic absorption in transparent electrodes is one of the main roadblocks to enabling power conversion efficiencies (PCEs) for perovskite‐based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device.
Erkan Aydin and coworkers from KAUST Photovoltaics Laboratory have recently shown the excellent properties of Zr‐doped indium oxide (IZRO) transparent electrodes for such applications, with improved near‐infrared (NIR) response compared to conventional tin‐doped indium oxide (ITO) electrodes. Optimized IZRO films feature very high electron mobility (up to ≈77 cm2 V−1 s−1), enabling highly infrared transparent films with a very low sheet resistance (≈18 Ω −1 for annealed 100 nm films). For devices, this translates to a parasitic absorption of only ≈5% for IZRO within the solar spectrum (250–2500 nm range), to be compared with ≈10% for commercial ITO.
Additionally, the team has reported 26.2% PCE for four‐terminal perovskite/silicon tandem devices with an absolute 3.5 mA cm−2 short‐circuit current improvement in silicon bottom cells is obtained by replacing commercial ITO electrodes with IZRO.