Photovoltaic devices and methods

A method of fabricating a photovoltaic device, the method comprising:

• (i) providing a semiconductor layer arranged on a first electrode;
• (ii) disposing a first liquid and a first amount of PbS quantum dots on the semiconductor layer;
• (iii)(a) drying the first liquid or (b) spin coating the semiconductor layer to remove substantially all of the first liquid from the first amount of PbS quantum dots;
• (iv) disposing a first amount of tetrabutylammonium iodide on the first amount of PbS quantum dots;
• (v) contacting the tetrabutylammonium iodide with a first rinsing liquid to remove at least a portion of the tetrabutylammonium iodide from the first amount of PbS quantum dots;
• (vi) optionally repeating steps (ii) to (v) one or more times;
• (vii) disposing a second liquid and a second amount of PbS quantum dots on the first amount of PbS quantum dots;
• (viii)(a) drying the second liquid or (b) spin coating the semiconductor layer to remove substantially all of the second liquid from the second amount of PbS quantum dots;
• (ix) disposing a first amount of 1,2-ethanedithiol on the second amount of PbS quantum dots;
• (x) contacting the 1,2-ethanedithiol with a second rinsing liquid to remove at least a portion of the 1,2-ethanedithiol from the second amount of PbS quantum dots;
• (xi) optionally repeating steps (viii) to (x) one or more times;
• and
• (xii) disposing a second electrode on the second amount of PbS quantum dots, wherein the disposing of the second electrode comprises (a) disposing a layer comprising Cr on the second amount of PbS quantum dots, and (b) disposing at least two contacts comprising Ag on the layer comprising Cr.