Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C₄H₉NH₃)₂PbI₄ under High Pressure

Due to their superior optical and electronic properties and good stability, 2D organic-inorganic halide perovskites (OIHPs) exhibit strong potential for optoelectronic applications. However, the large band gap, short carrier lifetime, and high resistance hinder their practical performance. In this work, the band gap is successfully tuned, the carrier lifetime is prolonged, and the resistance of (C₄H₉NH₃)₂PbI₄ (BA₂PbI₄) is reduced directly using high pressure. The band gap is decreased to less than 1 eV at 35.0 GPa, and the highest pressure is studied. The carrier lifetime at 9.9 GPa is 20 times longer than that at ambient conditions. Moreover, the resistance is reduced by four orders of magnitude at 34.0 GPa accompanying band gap narrowing. This work indicates that pressure plays an effective role in tuning the optical and electronic structures of BA₂PbI₄, and also provides a strategy to synthesize high-performance OIHP materials.