the perovskite material onto transparent substrates covered with a compact TiO 2 layer and an optional mesoporous TiO 2 (or Al 2 O 3 ) scaffold layer. [34] The p-i-n structure, which involves depositing the perovskite material onto transparent substrates which are covered with an HTL, such as the poly(3,4-ethylene dioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). [35] So far, PSCs based on both mesoporous and planar structure exhibit high performance and stability, however, the comparison of the advantages of two different strucutres in stability is still under debate. [36]
Mesoporous Perovskite Solar CellsRecently, a new generation of photovoltaic converters, mesoporous solar cell [37] has attracted more consideration due to their low material cost, simple fabrication process, high energy conversion efficiencies, [38] like dye-sensitized solar cell, [38c] and mesoporous perovskite solar cell. [5a,21,39] PCE up to 9.7% has been achieved by using CH 3 NH 3 PbI 3 (MAPbI 3 ) perovskite nanocrystals as the light absorber to fabricate a solid-state MPSC. [21] After that the research focuses on solid-state MSCs began to transfer from DSSCs to MPSCs. [32a,40] In an MPSC, a compact layer is usually deposited on fluorine doped tin oxide (FTO) layer, which usually extracts electrons and block holes. Three strategies are broadly used for depositing the TiO 2 layer: 1) Spin-coating the colloidal dispersion of TiO 2 nanoparticles followed by a thermal treatment (titanium source: TiCl 4 , [41] titanium isopropoxide, [42] tetra-n-butyl-titanate; [43] 2) spin-coating titanium precursor solutions followed by a thermal treatment (titanium source: TiCl 4 , [44] titanium isopropoxide, [23] titanium diisopropoxide bis(acetylacetonate) 12 ); 3) spray pyrolysis deposition (titanium source: titanium diisopropoxide bis(acetylaceto nate) 18 ). [45] Low-temperature sintering approaches to prepare an