Perovskite based charge transport layers for thin film optoelecronic devices and methods of making

Abstract

A new type of charge transport layer based on organometal halide perovskite for highly efficient organic light emitting diodes (OLEDs) is demonstrated. By solution processing of halide perovskite precursors, smooth essentially pure perovskite thin films may be prepared with high transparency and conductivity. Solution processed multilayer OLED with this perovskite-based hole transport layer outperforms a device with a PEDOT:PSS layer.

1 . A method for forming a charge transport layer of a thin film optoelectronic device, comprising:
 forming an organometal halide perovskite precursor;   coating a substrate with the organometal halide perovskite precursor to form an organometal halide perovskite layer;   passivating the organometal halide perovskite layer with a solvent during the coating step; and   annealing the passivated organometal halide perovskite layer.   
     
     
         2 . The method of  claim 1 , wherein the organometal halide perovskite precursor comprises a mixture of AX and BX 2 , where A is a cation, B is a metal, and X is a halide ion. 
     
     
         3 . The method of  claim 2 , wherein A comprises methylammonium (CH 3 NH 3 ), formamidinium (NH 2 CHNH 2 ), cesium (Cs), or mixtures thereof. 
     
     
         4 . The method of  claim 2 , wherein B comprises lead (Pb), tin (Sn), germanium (Ge), or mixtures thereof. 
     
     
         5 . The method of  claim 2 , wherein X comprises fluoride (F − ), chloride (Cl − ), bromide (Br − ), iodide (I − ), astatide (At − ), or mixtures thereof. 
     
     
         6 . The method of  claim 2 , wherein forming the organometal halide perovskite precursor comprises mixing AX and BX 2  in a solvent mixture of approximately 7 parts by volume dimethylformamide and approximately 3 parts by volume dimethylsulfoxide. 
     
     
         7 . The method of  claim 6 , wherein the resulting solvent mixture comprises approximately 0.64M AX and approximately 0.4 M BX 2 . 
     
     
         8 . The method of  claim 1 , wherein the organometal halide perovskite layer comprises methylammonium lead chloride (CH 3 NH 3 PbCl 3 ), formamidinium lead chloride (NH 2 CHNH 2 PbCl 3 ), cesium lead chloride (CsPbCl 3 ), or mixtures thereof. 
     
     
         9 . The method of  claim 1 , wherein coating the substrate comprises spin coating the organometal halide perovskite precursor onto the substrate. 
     
     
         10 . The method of  claim 9 , wherein a duration of the spin coating step comprises approximately 30 seconds, and the passivating solvent is added after approximately 6 seconds. 
     
     
         11 . The method of  claim 1 , wherein passivating the organometal halide perovskite layer comprises adding a low polarity organic solvent during the coating step. 
     
     
         12 . The method of  claim 11 , wherein the low polarity organic solvent comprises chloroform, chlorobenzene, toluene, or mixtures thereof. 
     
     
         13 . The method of  claim 1 , wherein annealing the passivated organometal halide perovskite layer comprises heating to approximately 100° C. for 10 minutes. 
     
     
         14 . A method for forming a charge transport layer of a thin film optoelectronic device, comprising:
 forming an organometal halide perovskite precursor by dissolving methylammonium chloride (CH 3 NH 3 Cl) and lead chloride (PbCl 2 ) in a mixture of dimethylformamide and dimethylsulfoxide;   coating a substrate with the organometal halide perovskite precursor to form a layer of methylammonium lead chloride (CH 3 NH 3 PbCl 3 ) on the substrate;   passivating the methylammonium lead chloride layer by adding a low polarity organic solvent during the coating step; and   annealing the passivated methylammonium lead chloride layer.   
     
     
         15 . The method of  claim 14 , wherein the organometal halide perovskite precursor comprises approximately 0.64 M methylammonium chloride and approximately 0.4 M lead chloride. 
     
     
         16 . The method of  claim 14 , wherein the low polarity organic solvent comprises chloroform, chlorobenzene, toluene, or mixtures thereof. 
     
     
         17 . An optoelectronic device, comprising:
 a first charge transport layer;   a photoactive layer; and   a second charge transport layer;   wherein one or both of the first and second charge transport layers comprise methylammonium lead chloride (CH 3 NH 3 PbCl 3 ) deposited from a mixture of methylammonium chloride (CH 3 NH 3 Cl) and lead chloride (PbCl 2 ) in a solution of dimethylformamide and dimethylsulfoxide, passivated with a low polarity organic solvent, and thermally annealed.   
     
     
         18 . The device of  claim 17 , wherein the mixture comprises approximately 0.64M methylammonium chloride and approximately 0.4 M lead chloride. 
     
     
         19 . The device of  claim 17 , wherein the photoactive layer comprises a light emitting layer. 
     
     
         20 . The device of  claim 17 , wherein the photoactive layer comprises a light harvesting layer.