Polymeric Hole‐Selective Contact for Crystalline Silicon Solar Cells

Carrier‐selective contacts based on inorganic materials (e.g., silicon layers and metal oxides) have been intensively investigated for efficient crystalline silicon (c‐Si) photovoltaics. Compared to the vacuum deposition process for inorganic films, organic semiconductors offer a simplified and low‐cost processing. Herein, solution‐processed poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl) amine] (PTAA) is developed as hole‐selective contact for c‐Si solar cells. PTAA exhibits a suitable band alignment with p‐type c‐Si, featuring a small valence band offset (≈0.1 eV) and a large conduction band offset (≈2.2 eV) for effective electron blocking. PTAA combined with Al2O3 passivation interlayer is demonstrated to simultaneously offer a low contact resistivity (36.5 mΩ cm2) and a moderate surface passivation (implied open‐circuit voltage 635.6 mV) on p‐type c‐Si surface. By the implementation of a full‐area hole‐selective Al2O3/PTAA rear contact, a champion efficiency of 20.2% is achieved on the hybrid c‐Si solar cells. Herein, a guiding principle for future research on polymeric carrier‐selective contact for c‐Si solar cells is provided.