Guard flow-enhanced organic vapor jet printing of photovoltaic donor materials in air

Abstract

We demonstrate the ability to rapidly deposit (local deposition rates well exceeding 1000Å/s) in air a small molecular electron donor material boron subphthalocyanine chloride (SubPc) for use in photovoltaic devices. The method employs a highly collimated jet of hot nitrogen gas carrying organic vapor toward a substrate, on which the organic molecules condense. A secondary jet of nitrogen coaxially surrounds the primary jet, shielding the organic vapor from the atmosphere. We study how the guard flow rate affects the printed film morphology and the resulting device properties. Notably, the crystallinity of the donor film can be increased while lowering the thin-film roughness, enhancing short circuit photocurrent nearly twofold over films printed without guard flow, allowing the photovoltaic power conversion efficiency of planar heterojunction SubPc/C60 cells to exceed 2% with SubPc deposited at ambient conditions.