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Chapter 11 • Hybrid Organic–Inorganic Metal Halide Perovskite Solar Cells  241








































                 FIGURE 11.5  (A) The photocurrent of the MAPbI 3  solar cells in planar device structure under 1-sun illumination, (B) EQE
                 of the solar cell with the active layer of MAPbI 3 . Adapted with the permission of Bi C, Wang Q, Shao Y, Yuan Y, Xiao Z,
                 Huang J. Nonwetting surface-driven high-aspect-ratio crystalline grain growth for efficient hybrid perovskite solar cells.
                 Nat Commun 2015;6, copyright 2015.

                 11.4.1  Solvent to Film Optimization

                 The solvent engineering strategy of using mixed solvents and/or anti-solvents has be-
                 come an effective but simple technique for realizing favorable perovskite film morphol-
                 ogy in order to achieve high-performance perovskite solar cells [73,74]. In the perovskite
                 film fabrication process, the precursor solution is prepared by dissolving in a mixture of
                 dimethylsulfoxide (dMSO) and γ-butyrolactone (GBL) and the solution is spun coated by
                 using one-step or two-step approach. dMSO is one of the commonly used solvent due to
                 its strong coordination with MX 2  to form metal-halide complexes [44,75]. dMSO is not the
                 only solvent that can produce high quality perovskite film as demonstrated by Wu et al.
                 [76]. Instead of using dMSO/GBL combination, Kim et al. [77] used a combination of N,N-
                 dimethylformamide (dMF) and GBL to prepare perovskite film with improved film qual-
                 ity. In the film fabrication process, application of antisolvent such as toluene is used to
                 extract excess solvent such as dMSO and dMF for the rapid precipitation of the perovskite
                 film before significant growth takes place [78]. The incorporation of toluene in film fabri-
                 cation process produces small-grain and dense perovskite films.
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