The ability to tune the bandgap of metal halide perovskites by alloying different halide ions is key to advancing tandem solar cells and light-emitting displays. However, this compositional flexibility also introduces challenges, most notably, the photoinduced migration of halide ions, which can degrade device performance. A prominent manifestation is photoinduced phase segregation in mixed-halide perovskites (MHPs), leading to the formation of iodide-rich and bromide-rich domains. These inhomogeneous regions act as charge carrier traps, reducing device efficiency. The thermodynamic and redox characteristics of halide perovskites create a strong driving force for hole trapping and the oxidation of iodide species. As a result, the mobility of halide ions and their vulnerability to hole-induced oxidation are major factors governing the long-term stability of perovskite solar cells.

Surface passivation of 3D perovskites using 2D perovskites, carbazole derivatives has been reported widely. However, interfacial chemistry can pose significant challenges during long-term solar cell operation. Under light and heat, cation migration can substantially alter the 2D/3D interface, leading to performance degradation. Therefore, suppressing both halide and cation migration is essential for enhancing the long-term stability and efficiency of perovskite solar cells and light-emitting devices.

Suggested Readings:

DuBose, J. T.; Kamat, P. V. Hole Trapping in Halide Perovskites Induces Phase Segregation, Accounts of Materials Research 2022, 3, 761-771.

DuBose, J. T.; Kamat, P. V. Energy Versus Electron Transfer: Managing Excited-State Interactions in Perovskite Nanocrystal–Molecular Hybrids, Chemical Reviews 2022, 122, 12475–12494.

Chakkamalayath, J.; Hiott, N.; Kamat, P. V. How Stable Is the 2D/3D Interface of Metal Halide Perovskite under Light and Heat?, ACS Energy Letters 2023, 8, 169-171.

Szabó, G.; Kamat, P. V., How Cation Migration across a 2D/3D Interface Dictates Perovskite Solar Cell Efficiency ACS Energy Letters 2024 9 (1), 193-200

Chakkamalayath, J. et al., Photon Management Through Energy Transfer in Halide Perovskite Nanocrystal–Dye Hybrids: Singlet vs Triplet Tuning. Accounts of Chemical Research 2025, 58, 1461–1472.