Surface engineering of SnO₂ for improved perovskite/SnO₂ photodetectors

Lead halide perovskite (LHP) heterojunctions have proven to be promising for achieving low-cost and efficient photodetection. However, the remarkable interfacial non-radiative recombination severely deteriorated the performance of the resulting devices. Herein, surface engineering of SnO₂ with ammonium tetrathiotungstate ((NH₄)₂WS₄) has been proposed to effectively passivate the interfacial defects at the LHP CH₃NH₃PbI₃/SnO₂ interface to fabricate high-performance photodetectors (PDs). Experimental and theoretical studies showed that the surface engineering with (NH₄)₂WS₄ resulted in S substituting for oxygen lattice of SnO₂, which passivated the surface oxygen vacancies of SnO₂. Further studies have shown that the S atoms at the surface of SnO₂ further suppressed the I vacancies and Pb vacancies at the bottom surface of CH₃NH₃PbI₃. Finally, improved CH₃NH₃PbI₃/SnO₂ PDs with the responsivity and detectivity of 0.41 A W^-1 and 5 × 10¹² Jones, respectively, at zero bias, have been demonstrated. The results presented in this work provide promising pathways to effectively passivate the interfacial defects of LHP/SnO₂ heterojunctions for achieving efficient photodetection in the future.