Reducing sputter damage-induced recombination losses during deposition of the transparent front-electrode for monolithic perovskite/silicon tandem solar cells

Many research groups work on overcoming the 30% power conversion efficiency (PCE) level for perovskite/silicon tandem solar cells with various approaches. The most common tandem architectures employ a transparent conductive oxide (TCO) front electrode. Due to its fast deposition and up-scalability, sputter deposition is the preferred method for TCO deposition. The sensitive layers of perovskite solar cells are protected from sputter damage by a thermal atomic layer (ALD) deposited tin oxide (SnO2) buffer layer, which induces parasitic absorption. Here, we propose a method to reveal the impact of sputter damage on SnO2 buffer layer-free devices. By performing light intensity-dependent current density-voltage (J-V) measurements and thereby reconstructing the single-junction solar cell pseudo J-V characteristics, we could associate sputter damage with trap-assisted non-radiative recombination losses. Additionally, we demonstrate a simple method to minimize sputter damage to the perovskite solar cell to the point where a protective SnO2 buffer layer is no longer required. By lowering the sputter power density during the TCO deposition, we regained ∼13 mV open-circuit voltage and ∼3% fill factor of the devices, improving the efficiency from 13.55 to 14.17%. We show that these improvements are linked to a reduction of transport and non-radiative recombination losses. Finally, we fabricated optically superior and sputter damage-free monolithic perovskite/silicon tandem devices without needing a protective SnO2 buffer layer. By doing so, we increased the tandem device current density by 0.52 mA/cm2, representing a crucial step toward further optimizing the optical performance of tandem devices.