A resonance spacer cation-based heterostructure enables efficient and stable perovskite solar cells

Ammonium salts are essential low-dimensional perovskite materials and are synthesized by a protonation reaction, giving the amino group a positive charge. Here, 2-amino-3-methylthiazol-3-ium iodide (AMTI) and 2-amino-3-methylbenzo[d]thiazol-3-ium iodide (AMBTI) were synthesized via an N-methylation reaction in an attempt to obtain resonance iminium salts, which were used to build a low-dimensional perovskite. The construction of the two-dimensional (2D) perovskite (AMBT)2PbI4 confirmed that the positive charge of AMBT+ can be delocalized from thiazole N to amino N, whereas AMT+ merely cut PbI2 to form the (one-dimensional) 1D chain AMTPbI3. AMTI-modified 1D/3D devices performed poorly due to the interfacial capacitance created by the tip discharge, which limits carrier transport. In contrast, the AMBTI treatment improved the device's performance; meanwhile, the final 2D/3D PSC achieved a power conversion efficiency of 24.2% and showed excellent stability. Ultimately, we propose an unprecedented approach to establish the resonance spacer cation of low-dimensional perovskite heterojunctions and elaborated on the effect of different dimensions on the device performance. Ammonium salts are essential low-dimensional perovskite materials and are synthesized by a protonation reaction, giving the amino group a positive charge.