With the rapid development of organic-inorganic lead halide perovskite photovoltaics, increasingly more attentions are paid to explore the growth mechanism and precisely control the quality of perovskite films. In this study, we propose a "stitching effect" to fabricate high quality perovskite films by using chlorobenzene (CB) as an anti-solvent and isopropyl alcohol (IPA) as an additive into this anti-solvent. Because of the existence of IPA, CB can be efficiently released from the gaps of perovskite precursors and the perovskite film formation can be slightly modified in a controlled manner. More homogeneous surface morphology and larger grain size of perovskite films were achieved via this process. The reduced grain boundaries ensure low surface defect density and good carrier transport in the perovskite layer. Meanwhile, we also performed the Fourier transform infrared (FTIR) spectroscopy to investigate the film growth mechanism of unannealed and annealed perovskite films. Solar cells fabricated by using the "stitching effect" exhibited a best efficiency of 19.2%. Our results show that solvent and solvent additives dramatically influenced the formation and crystallization processes for perovskite materials due to their different coordination and extraction capabilities. This method presents a new path towards controlling the growth and morphology of perovskite films.

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The flexible perovskite photodetector, fabricated by a modified one-step method, showed a broadband spectrum response from blind ultraviolet to visible light, and exhibited excellent mechanical flexibility and improved environmental stability.

optical properties. However, such materials are either expensive or require vacuum equipment, e.g., metal-organic chemical vapor deposition, to fabricate, [7][8][9] which places a restriction on a wide deployment. In recent years, organometal trihalide perovskites (OTPs) (with a structure of ABX 3 , where A is an organic cation CH 3 NH 3 + (MA), B is Pb 2+ , X is a halide anion or mixed halide) have drawn great attention and been a very promising candidate for opto-electronic applications due to low cost and high throughput solution process. Since the discovery of perovskitebased solar cells (PSCs) by Miyasaka and co-workers [10] power conversion efficiencies have exceeded 22% in less than seven years, [11] thanks to the outstanding physics properties, including the low exciton binding energy, strong light absorption, long carrier lifetime, large carrier diffusion coefficient, and low charge recombination rate. [12][13][14][15][16] These features also make the emerging perovskite materials a promising alternative to conventional semiconductors used in PDs. Indeed, solution-processed OTPs have yielded PDs with excellent device performance. [16][17][18][19][20][21][22][23][24] For instance, both polycrystalline films and single crystals of OTPs have been successfully used to fabricate the narrowband and broadband photodetectors. [25][26][27] As one of the earliest discovered and extensively researched perovskite materials, MAPbI 3 has been regarded as one of the most potential materials for PDs due to its broadband absorption and superb light sensitivity. Dong et al. reported a MAPbI 3 -based photodetector with excellent photoconductive properties. [20] Su et al. reported a self-powered photodetector based on MAPbI 3, which exhibited excellent responsivity and rapid response time for wavelength ranging from ultraviolet to visible light. [28] Chen et al. fabricated a flexible UV-vis-NIR photodetector based on MAPbI 3 with excellent mechanical flexibility and durability. [18] However, some issues about this material still exist. MAPbI 3 tends to degrade and dissociate into MAI and PbI 2 in air. [29][30][31] Recent work on FAPbX 3 (FA: CH 3 (NH 2 ) 2 + , X = I, Br, Cl) PSCs demonstrates better thermal durability than methylammonium perovskites. [31,32] However, FAPbI 3 has two different phases at room temperature: α-phase (desired perovskite phase) and δ-phase (photo-inactive phase). Also, the α-phase perovskite of FAPbI 3 , which is sensitive to solvents and moisture, would turn into the undesired δ-phase in an air atmosphere. [33] Photodetectors, which can convert light signals into electrical signals, are important opto-electronic devices in imaging, optical communication, biomedical/biological sensing, and so on. Here a solution-processed photodetector based on the triple cation perovskite is demonstrated. The perovskite photodetectors show a high detectivity, high speed, as well as excellent environmental stability. Operating at a low voltage bias of 2 V, the photodetectors exhibit a large on/off ratio of 10 5 , ...

While most work carried out to date has focused on the solvent annealing of perovskite, in the present work, we focused on the solvent annealing of lead iodide. Based on the two-step spin-coating method, we designed a screening method to search for an effective solvent annealing process for PbI. PbI films were annealed in diverse solvent atmospheres, including DMF, DMSO, acetone, and isopropanol (IPA). We found that the solvent annealing of PbI in the DMF, acetone, and IPA atmospheres resulted in dense PbI films, which impeded the complete conversion of PbI to CHNHPbI. Surprisingly, employing the DMSO solvent annealing process for PbI led to porous PbI, which facilitated the complete conversion of PbI to perovskite with larger grain sizes. Solar cells fabricated using the DMSO solvent annealing process exhibited the best efficiency of 18.5%, with a fill factor of 76.5%. This unique solvent annealing method presents a new way of controlling the perovskite film quality for highly efficient solar cells.