Efficient Charge Extraction in Thick Bulk Heterojunction Solar Cells through Infiltrated Diffusion Doping

Abstract

A new strategy for improving the charge extraction in thick bulk heterojunction (BHJ) polymer solar cells (PSCs) is reported. By the deposition of a solution-processed vanadium oxide (s-VOx) onto BHJ active layers, conductive charge-transport channels are formed inside the active layer via a charge-transfer doping reaction between the lone-pair electrons of the sulfur atoms in the polymer and the Lewis-acidic vanadium atoms of the s-VOx. Because the charge-transport channels significantly reduce charge recombination in the BHJ films, high internal quantum efficiencies (IQEs) of over 80% are achieved in the thick inverted PSCs (approximate to 420 nm). This finding represents a new strategy for improving the efficiency and feasibility of printable photovoltaic devices.