Annealing (glass)

Phase (matter)

Engineering

Materials science

Mineralogy

Layer (electronics)

Grain growth

Perovskite (structure)

In situ

Chemical engineering

Grain boundary

Thermodynamics

Grain size

Physics

Nanotechnology

Organic chemistry

Microstructure

Surface modification

Composite material

Ionic bonding

Chemistry

Nucleation

Passivation

Advanced Energy Materials

The phase instability and large energy loss are two obstacles to achieve stable and efficient inorganic‐CsPbI 3− x Br x perovskite solar cells. In this work, stable cubic perovskite (α)‐phase CsPbI 2 Br is successfully achieved by Pb(Ac) 2 functioning at the grain boundary under low temperature. Ac − strongly coordinates with CsPbI 2 Br to stabilize the α‐phase and also make the grain size smaller and film uniform by fast nucleation. PbO is formed in situ at the grain boundary by decomposing Pb(Ac) 2 at high‐temperature annealing. The semiconducting PbO effectively passivates the surface states, reduces the interface recombination, and promotes the charge transport in CsPbI 2 Br perovskite solar cells. A 12% efficiency and good stability are obtained for in situ PbO‐passivated CsPbI 2 Br solar cells, while Pb(Ac) 2 ‐passivated device exhibits 8.7% performance and the highest stability, much better than the control device with 8.5% performance and inferior stability. This article highlights the extrinsic ionic grain boundary functionalization to achieve stable and efficient inorganic CsPbI 3− x Br x materials and the devices.

In Situ Grain Boundary Functionalization for Stable and Efficient Inorganic CsPbI<sub>2</sub>Br Perovskite Solar Cells

In Situ Grain Boundary Functionalization for Stable and Efficient Inorganic CsPbI2Br Perovskite Solar Cells

In Situ Grain Boundary Functionalization for Stable and Efficient Inorganic CsPbI₂Br Perovskite Solar Cells