Thiophene-Based Polyelectrolyte Boosts High- Performance Quasi-2D Perovskite Solar Cells with Ultralow Energy Loss

The rise of quasi-2D perovskite structures holds great promise for highly efficient and stable perovskite solar cells (PCSs). As such, fabricating large-area quasi-2D perovskite solar cells (PCSs) with high power conversion remains under active exploration. We identified that maintaining the homogeneous crystalline orientation upon scaling up is a key challenge. Thus, we introduce a thiophene-based polyelectro-lyte as the hole transporting layer (HTL) to facilitate large area quasi-2D PCSs fabrication with high performance. The HTL with carboxyl acid anchoring groups can be attached to various conducting metal oxide substrates, enabling a conformal self-assembled monolayer (SAM). This SAM surface facilitates the quasi-2D perovskite crystal growth vertically aligned to the substrate. Along with a favorable energy alignment, a high open-circuit voltage (VOC) of 1.24 V was achieved, approaching the Shockley-Queisser optimal limit (VOC = 1.34 V). Remarkably, the device maintained over 80% of its initial efficiency after operating at the maximum power point under simulated AM1.5G solar irradiation for 1000 h at a relative humidity of 60%. These findings offer new fabrication strategies, paving the way to scalable quasi-2D PCS production with high efficiencies.