Soft-Sputtered ITO as Top Electrode for Inverted Perovskite Solar Cells

Transparent conductive oxides (TCOs), particularly indium tin oxide (ITO), are critical for enabling advanced photovoltaic architectures such as bifacial, tandem, and semitransparent devices. However, direct sputter deposition of ITO onto layers in halide perovskite solar cells (PSCs) remains challenging due to energetic particle-induced damage and poor film quality at low processing temperatures. Here, the use of ion-beam-assisted soft sputtering to deposit ITO as the top electrode for inverted perovskite solar cells is demonstrated. This approach employs reduced ion energy to minimize damage and produces high-quality ITO films without post-annealing, resulting in enhanced device performance and yield. Conventional sputtering results in severe device degradation, with power conversion efficiency (PCE) dropping from 19.6 ± 1.0% for an evaporated Ag electrode to 8.4 ± 1.7% for sputtered ITO, and device yield decreasing from ∼92% to ∼42%. This performance drop is attributed to interfacial damage and high ITO sheet resistance (106 ± 8 Ω sq−1). In contrast, optimized soft sputtering produces crystalline ITO films with reduced sheet resistance (43 ± 0.4 Ω sq−1), improving device performance to 13.4 ± 1.6% PCE and ∼67% yield. Further incorporation of an ultrathin Ag interlayer (≈2 nm) enhances interfacial contact and conductivity, resulting in devices with PCE up to 14.3 ± 0.6% and ∼83% yield. This work establishes a viable pathway for integrating sputtered ITO electrodes on damage-sensitive organic and perovskite layers, laying the groundwork for the application of soft sputtering in depositing TCOs for scalable transparent and semitransparent photovoltaic devices.