Passivating contacts based on transition metal oxides (TMOs) have the potential to overcome existing performance limitations in high‐efficiency crystalline silicon (c‐Si) solar cells, which is a significant driver for continuing cost/Watt reductions of photovoltaic electricity. Herein, innovative stacks of Al‐alloyed TiO x (Al y TiO x ) and pure TiO x as transparent electron‐selective passivating contacts for n‐type c‐Si surfaces are explored. An optimized stack of 2 nm Al y TiO x and 2 nm TiO x is shown to provide both record‐quality surface passivation and excellent electrical contact, with a surface recombination current density prefactor J 0 of 2.4 fA cm−2 and a specific contact resistivity ρ c of 15.2 mΩ cm2. The performance of this innovative stack significantly exceeds previously reported values for pure or doped TiO x single layers, SiO x /TiO x stacks, a‐Si:H/TiO x stacks, and other transparent contact technologies. Furthermore, an excellent efficiency of 21.9% is attained by incorporating the optimized stack as a full‐area rear contact in an n‐type c‐Si solar cell. The findings set a new benchmark for the passivation performance of metal oxide‐based passivating contacts, bringing it to a level on par with state‐of‐the‐art SiO x /poly‐Si contacts while greatly improving optical transparency.

To reduce the cost of solar photovoltaic electricity generation by overcoming current performance limitations in crystalline silicon (c-Si) solar cells, it is essential to switch from current silicon-based materials to more transparent materials as carrier-selective passivating contacts (CSPCs). Ideal CSPCs should perform three functions simultaneously: they should 1) passivate the silicon dangling bonds in order to provide low surface recombination current density prefactor J 0 (≤10 fA cm −2 ) which ensures high open-circuit voltages at a cell level; 2) operate as efficient contacts for either electrons or holes, with low contact resistivity (≤100 mΩ cm 2 ) to allow high fill factors; and 3) should be highly transparent in the wavelength range corresponding to the solar spectrum in order to reduce parasitic optical losses and hence enable high short-circuit current densities, particularly when applied to the front (illuminated) side of devices. In order to enable practical applications, they should also be thermally stable and prepared using earth-abundant materials. Multiple recent review articles have provided an overview of the development of passivating contact technology in silicon solar cells, testifying to the great interest in this topic. [1] Among passivating contact technologies, those based on hydrogenated amorphous Si (a-Si:H) and polycrystalline Si (poly-Si) layers represent the current state-ofthe-art, having enabled multiple silicon solar cells with worldrecord efficiencies in recent years. [2] However, these materials suffer from significant parasitic optical absorption, which imposes a limit on their ability to provide further improvements in device performance.Transition metal oxides (TMOs) are the leading candidate to replace Si-based materials as CSPCs in order to overcome these limitations. TMOs are very versatile since they can be utilized as both hole-selective contacts, such as MoO x , [3] VO x , [4] and WO x , [5] and electron-selective contacts, such as TiO 2 and ZnO. This is due to the fact that their work functions span a wide range from 3 to 7 eV. [6] Furthermore, TMOs are inexpensive, nontoxic, based on earth-abundant materials, compatible Passivating contact technologies are essential for fabricating high-efficiency crystalline silicon (c-Si) solar cells, and their application and incorporation into manufacturing lines has ranked as a hot topic of research. Generally, ideal passivating contacts should combine excellent electrical contact, outstanding surface passivation, and high optical transparency. However, addressing all these criteria concurrently is challenging since it is unlikely for any single material to exhibit both efficient carrier transport and surface-defect passivation while demonstrating negligible parasitic absorption. In this work, several earth-abundant, wide-bandgap materials are combined to engineer highquality transparent electron-selective passivating contact structures capable of overcoming these obstacles. A highly transparent Al y TiO x /ZnO/TiO 2 stack...

Imaging In article number http://doi.wiley.com/10.1002/solr.202100348, Anh Dinh Bui, Daniel Macdonald, Hieu T. Nguyen, and co‐workers report a fast, non‐invasive, camera‐based method to image pseudo current density ‐ voltage curves of various perovskite‐based structures from partially finished to finished cells with micron‐scale spatial resolution. This approach is useful to resolve the inhomogeneity of implied open‐circuit voltage and maximum fill factor across the devices, and their evolution during degradation.

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Early prediction of spatially resolved performance of perovskite solar cells (PSCs) is essential for process monitoring, control and fault diagnosis, and upscaling of this emerging technology. Herein, a fast, nonde structive, contactless imaging‐based approach is developed to visualize the spatial distribution of possible light current density−voltage (pseudo‐J−V) curves on finished and partly finished cells. This allows for the extraction of other critical spatially resolved properties including implied open‐circuit voltage and pseudo‐fill factor. The technique is applied to systematically investigate various degradation behaviors on PSCs including thermal stability, light soaking, and ambient air exposure. Finally, it is used to predict pseudo‐J−V curves of various perovskite films with different compositions. These results demonstrate the significant value of this fast imaging technique for the research and development of PSCs ranging from material selection, process optimization, to degradation study.