Solvent-assisted crystallization via a delayed-annealing approach for highly efficient hybrid mesoscopic/planar perovskite solar cells

- A new approach to improve the morphology and performance of CH3NH3PbI3 perovskite.
- Optimization of one step spin-coating solvent-assisted crystallization method.
- Effect of delayed annealing on surface morphology of perovskite is revealed.
- A simple procedure to obtain reproducible devices with all commercial materials.

The formation of a dense and uniform perovskite film with large grain is an important factor for getting excellent device performance. Here, we report an optimized solvent-assisted crystallization procedure followed by a delayed annealing for easy and reproducible fabrications of perovskite solar cells with a hybrid mesoscopic configuration. The working electrode contains a mesoporous TiO2 scaffold layer of 100 nm deposited on FTO substrate with a thin TiO2 blocking layer. The devices in this study were assembled using all commercially available materials without any extensive modification. Formation of uniform and pin-hole free perovskite nanocrystals with film thickness 200 nm on top of the scaffold layer was achieved via an optimized solvent-assisted crystallization method. A much smoother perovskite layer was achieved with a delayed annealing for a certain period. The best performing device was obtained at the annealing delayed for 60 min, giving the power conversion efficiency 16.9% with an average value 15.4% obtained from 60 devices.

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