FIELD

The disclosed subject matter relates generally to photonic curing of nanocrystals, and to methods and devices using the photonic cured nanocrystals.

BACKGROUND

Colloidal semiconductor nanocrystals are of interest in low-cost, high efficiency photovoltaic (PV) devices (Stolle et al., “Nanocrystal photovoltaics: a review of recent progress,”Curr. Opin. Chem. Eng.2.2(2013):160-167). Nanocrystals can be synthesized in large quantities, dispersed in solvents, and deposited under ambient conditions on virtually any type of substrate. The highest efficiency reported for a nanocrystal PV without high-temperature processing is 7% for PbS nanocrystals (Ip et al., “Hybrid passivated colloidal quantum dot solids,”Nat. Nanotechnol.,7(9):577-582, 2012). High temperature sintering has been used to achieve higher efficiencies, of up to 12% for nanocrystals of CdTe (Panthani et al., “High Efficiency Solution Processed Sintered CdTe Nanocrystal Solar Cells: The Role of Interfaces,”Nano Lett., December 2013), Cu(In,Ga)Se2(CIGS) (Harvey et al., “Copper Indium Gallium Selenide (CIGS) Photovoltaic Devices Made Using Multistep Selenization of Nanocrystal Films,”ACS Appl. Mater. Interfaces,5(18):9134-9140, 2013), Cu(In,Ga)S2(Guo et al., “Ink formulation and low-temperature incorporation of sodium to yield 12% efficient Cu(In,Ga)(S,Se)2solar cells from sulfide nanocrystal inks,”Prog. Photovolt. Res. Appl.,21(1):64-71, 2013), and Cu2ZnSnS4(Guo et al., “Fabrication of 7.2% Efficient CZTSSe Solar Cells Using CZTS Nanocrystals,”J. Am. Chem. Soc.,132(49):17384-17386, 2010). High-temperature processing, however, adds significant manufacturing cost—especially for CuInSe2and CIGS nanocrystals, which require heating under a selenium-rich atmosphere to induce sintering (selenization). To eliminate the need for high temperature selenization and still achieve reasonably high device efficiency from ink-processed CuInSe2and CIGS nanocrystal devices, as well as to allow coating a variety of substrates not currently accessible, improved methods are needed. The systems, compositions, methods, and devices disclosed herein address these and other needs.

SUMMARY

Disclosed herein, in one aspect, compositions and methods of making and using such compositions. In a further aspect, disclosed herein are methods of making a semiconductor layer from nanocrystals. In the disclosed methods a film of nanocrystals capped with a ligand can be deposited onto a substrate; and the nanocrystals can be irradiated with one or more pulses of light. Various coated and uncoated substrates can be used, as disclosed herein. The pulsed light can be used to substantially remove the ligands from the nanocrystals and leave the nanocrystals unsintered or sintered, thereby providing a semiconductor layer. Layered structures comprising these semiconductor layers with an electrode are also disclosed. Devices comprising such layered structures are also disclosed.

In a further aspect, disclosed are methods of making a layer from nanocrystals that comprises depositing a film of nanocrystals with various surface agents onto a substrate; and then irradiating the nanocrystals with one or more pulses of light. Examples of surface agents discussed herein are ions and dispersants. Various coated and uncoated substrates can be used, as disclosed herein. The pulsed light can be used to substantially remove the surface agents from the naocrystals and leave the nanocrystals unsintered or sintered, thereby providing a semiconductor layer. Layered structures comprising these semiconductor layers with an electrode are also disclosed. Devices comprising such layered structures are also disclosed.

Additional advantages of the disclosed systems, compositions, methods, and devices will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the disclosed process. The advantages of the disclosed systems, compositions, methods, and devices will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed process, as claimed.

