Page - 105 - in Photovoltaic Materials and Electronic Devices

perovskite  in  some  cases.  Returning  to  Figure  5,  if  excess  of  MACl  breaks  down  the  growth  along  the  (110)  plane,  we  believe  MACl  can  also  break  down  the  crystalline  order  range.  Since  a  large  amount  of  MAPbI3  existed  in  the  amorphous  phase  form,  the  cubic  phase  of  MAPbI3  may  be  more  favorable  in  short  crystalline  order  range  than  the  tetragonal  phase.      Figure  5.  XRD  patterns  of  MAPbI3‐xClx  prepared  from  (A)  precursor  solution  xPbCl2+yPbI2+zMAI    (x  =  0.25,  0.5,  0.75  and  1;  y  =  1  −  x;  z  =  3  ×  x  +  y)  in  DMF;  and  (B)  precursor  solution  1PbI2+1MAI+xMACl  (x  =  0.5,  1,  1.5  and  2).  Reprinted  from  reference  [27],  Copyright  ©  2014,  American  Chemical  Society.  Figure 5. XRD patterns of MAPbI3-xClx prepared from (A) precursor solution xPbCl2+yPbI2+zMAI(x=0.25,0.5,0.75and1;y=1´x;z=3ˆx+y) inDMF;and (B)precursorsolution1PbI2+1MAI+xMACl(x=0.5,1,1.5and2). Reprintedfrom reference [27],Copyright©2014,AmericanChemicalSociety. There are other influences associated with Cl´. Increasing the temperature duringthesoakingof thePbI2 substrate inMAI+MAClIPAsolutioncanimprove the (110) orientation of MAPbI3-xClx where the high temperature facilitates the expellingofMACl[97]. AnnealingtheMACl:PbI2 (3:1)precursoroncompactTiO2 at 60˝C for 10 min followed by 100˝C for 20 min instead of gradually heating from 25 to100˝Cfor45minresultedinthe(200)crystalplaneofMAPbI3-xClx beingvertically aligned on the substrate [98]. The tetragonal phase MAPbI3-xClx was occasionally found on compact TiO2 substrate [53], while the cubic phase always occurred in meso-porous substrate, where the trapped MACl in meso-porous structure [8] helps the formation ofcubic phase. While thesize ofMAPbI3 crystalgrains are smallerbut thedegreeofcrystallinity improves in thepresenceofMACl[27,54], thesequential depositedMAPbI3-xClx results in (001)elongatedcrystals [13]. 4. Conclusions In thisarticle, the locationofCl´andits influenceonthecrystalmorphology of MAPbI3-xClx is summarized, where the deposition methods (one step deposition, sequential deposition and vapor based deposition) for MAPbI3-xClx are reviewed. Furthermore, the cubic and tetragonal phases of MAPbI3 are elucidated and the crystallization process of MAPbI3-xClx is also summarized. Detailed information about the crystal structure with variable deposition parameters is also discussed. Though a recent report showed that Cl´mainly improves the carrier transport at theperovskite/Spiro-MeOTADandperovskite/TiO2 interfaces, rather thanwithin the perovskite crystals, the authors of reference [99] more recently spatially resolved photoluminescence decay results showed less recombination in the high chlorine 105