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We report an organic luminescent small molecule, Bis(1-phenylisoquinoline) (acetylacetonate) iridium(III) or Ir(piq)2(acac), that can function as a stable and efficient hole selective contact (HSC) for crystalline silicon (c-Si) solar cells. The devices with the Ir(piq)2(acac) HSC exhibit superior charge transport properties and high stability for up to 30 days in the air without packaging. The photovoltaic characteristics with the solution-processed Ir(piq)2(acac) HSC exhibit little dependence on the blade coating speed and film thickness, demonstrating tolerance to coating and thickness variations. Moreover, the series resistance of the solar cells and the surface work function of the Ir(piq)2(acac) HSCs exhibit analogous correlations to the annealing temperature, suggesting that the fill factor (FF) enhancement originates from an upward energy band bending and a reduced barrier height which facilitates hole transport and collection. The conventional c-Si solar cell incorporating an Ir(piq)2(acac) HSC achieves a 17.8% power conversion efficiency (PCE) with a 78.9% FF, both exceeding the reference counterpart with a 16.9% PCE and 76.8% FF. This work opens up possibilities for exploring a variety of organic luminescent small molecules as efficient hole selective contacts in high-efficiency and low-cost silicon photovoltaics. Graphic Abstract

High pattern fidelity is paramount to the performance of metalenses and metasurfaces, but is difficult to achieve using economic photolithography technologies due to low resolutions and limited process windows of diverse subwavelength structures. These hurdles can be overcome by photomask sizing or reshaping, also known as optical proximity correction (OPC). However, the lithographic simulators critical to model-based OPC require precise calibration and have not yet been specifically developed for metasurface patterning. Here, we demonstrate an accurate lithographic model based on Hopkin’s image formulation and fully convolutional networks (FCN) to control the critical dimension (CD) patterning of a near-infrared (NIR) metalens through a distributed OPC flow using i-line photolithography. The lithographic model achieves an average ΔCD/CD = 1.69% due to process variations. The model-based OPC successfully produces the 260 nm CD in a metalens layout, which corresponds to a lithographic constant k1 of 0.46 and is primarily limited by the resolution of the photoresist. Consequently, our fabricated NIR metalens with a diameter of 1.5 mm and numerical aperture (NA) of 0.45 achieves a measured focusing efficiency of 64%, which is close to the calculated value of 69% and among the highest reported values using i-line photolithography.