Secondary treatment of films of colloidal quantum dots for optoelectronics and devices produced thereby

Abstract

A method of forming an optoelectronic device. The method includes providing a deposition surface and contacting the deposition surface with a ligand exchange chemical and contacting the deposition surface with a quantum dot (QD) colloid. This initial process is repeated over one or more cycles to form an initial QD film on the deposition surface. The method further includes subsequently contacting the QD film with a secondary treatment chemical and optionally contacting the surface with additional QDs to form an enhanced QD layer exhibiting multiple exciton generation (MEG) upon absorption of high energy photons by the QD active layer. Devices having an enhanced QD active layer as described above are also disclosed.

What is claimed is: 
     
         1 . A method of forming an optoelectronic device comprising:
 providing a deposition surface;   contacting the deposition surface with a ligand exchange chemical and contacting the deposition surface with a quantum dot (QD) colloid over one or more cycles to form an initial QD film on the deposition surface; and   contacting the QD film with a secondary treatment chemical.   
     
     
         2 . The method of forming an optoelectronic device of  claim 1  wherein the step of contacting the initial QD film with a secondary treatment chemical comprises contacting the initial QD film with a secondary treatment chemical and contacting the deposition surface with a quantum dot (QD) colloid over one or more cycles to deposit additional QDs on the initial QD film. 
     
     
         3 . The method of forming an optoelectronic device of  claim 2  wherein the secondary treatment chemical is at least one of hydrazine, formic acid, mercaptopropionic acid, an organic acid, methylamine, methanol, ethanol and ethylenediamine. 
     
     
         4 . The method of forming an optoelectronic device of  claim 2  wherein the initial QD film is formed to a thickness of about 40 nm to 400 nm. 
     
     
         6 . The method of forming an optoelectronic device of  claim 2  wherein the initial QD film is thickened by about 1 nm to 50 nm by the deposition of additional QDs in the secondary treatment step. 
     
     
         7 . The method of forming an optoelectronic device of  claim 1  wherein the step of contacting the initial QD film with a secondary treatment chemical comprises contacting the initial QD film with a secondary treatment chemical over one or more cycles without depositing additional QDs on the QD film. 
     
     
         8 . The method of forming an optoelectronic device of  claim 7  wherein the secondary treatment chemical is at least one of hydrazine, formic acid, mercaptopropionic acid, an organic acid, methylamine, methanol, ethanol and ethylenediamine. 
     
     
         9 . A method of forming a solar cell comprising:
 providing a substrate;   forming a first electrode in contact with the substrate;   contacting the first electrode with a ligand exchange chemical and contacting the first electrode with a quantum dot (QD) colloid over one or more cycles to form an initial QD film in contact with the first electrode;   contacting the initial QD film with a secondary treatment chemical; and   forming a second electrode in contact with the initial QD film, not in contact with the first electrode.   
     
     
         10 . The method of forming a solar cell of  claim 9  wherein the step of contacting the initial QD film with a secondary treatment chemical comprises contacting the initial QD film with a secondary treatment chemical and contacting the deposition surface with a quantum dot (QD) colloid over one or more cycles to deposit additional QDs on the initial QD film. 
     
     
         11 . The method of forming a solar cell of  claim 10  wherein the secondary treatment chemical is at least one of hydrazine, formic acid, mercaptopropionic acid, an organic acid, methylamine, methanol, ethanol and ethylenediamine. 
     
     
         12 . The method of forming a solar cell of  claim 10  wherein the initial QD film is formed to a thickness of about 40 nm to 400 nm. 
     
     
         13 . The method of forming a solar cell of  claim 10  wherein the initial QD film is thickened by about 1 nm to 50 nm by the deposition of additional QDs in the secondary treatment step. 
     
     
         14 . The method of forming a solar cell of  claim 9  wherein the step of contacting the initial QD film with a secondary treatment chemical comprises contacting the QD film with a secondary treatment chemical over one or more cycles without depositing additional QDs on the QD film. 
     
     
         15 . The method of forming a solar cell of  claim 14  wherein the secondary treatment chemical is at least one of hydrazine, formic acid, mercaptopropionic acid, an organic acid, methylamine, methanol, ethanol and ethylenediamine. 
     
     
         16 . The method of forming a solar cell of  claim 9  further comprising forming a doped window layer in contact with the first electrode and the initial QD film. 
     
     
         17 . A solar cell comprising:
 a first electrode;   a QD active layer in electrical contact with the first electrode providing for multiple exciton generation (MEG) upon absorption of photons by the QD active layer; and   a second electrode in electrical contact with the QD active layer.   
     
     
         18 . The solar cell of  claim 17  further comprising a doped window layer in electrical contact with the first electrode and the QD active layer. 
     
     
         19 . The solar cell of  claim 17  wherein the QD active layer comprises at least one of QDs of lead selenide (PbSe), lead sulfide (PbS), cadmium selenide (CdSe), other semiconductor nanocrystals (NCs), core-shell and ternary nanocrystals, for example lead telluride (PbTe), lead selenide sulfide (PbSSe), lead selenide core with lead sulfide shell, cadmium lead sulfide (CdPbS), cadmium lead selenide (CdPbSe) tin sulfide (SnS), tin selenide (SnSe), tin telluride (SnTe), silicon (Si), germanium (Ge), indium arsenide (InAs), indium phosphide (InP), indium antimonide (InSb), gallium arsenide (GaAs), indium gallium arsenide (InGaAs) and NC structures of all other Group IV, II-VI, IV-VI compounds and alloys. 
     
     
         20 . The solar cell of  claim 19  further comprising a glass substrate.