Tin(II) thiocyanate Sn(SCN)${}_2$ as an ultrathin anode interlayer in organic photovoltaics

Abstract

We report the application of a coordination polymer semiconductor, tin(II) thiocyanate [Sn(SCN)${}_2$] as an ultrathin anode interlayer in organic photovoltaics (OPVs). Sub-10 nm layers of Sn(SCN)${}_2$ with high smoothness and excellent transparency having an optical band gap of 3.9 eV were deposited from an alcohol-based solution at room temperature without post-deposition annealing. Inserting Sn(SCN)${}_2$ as an anode interlayer in polymer:fullerene OPVs drastically reduces the recombination loss due to the exciton-blocking energy levels of Sn(SCN)${}_2$. At the optimum thickness of 7 nm, an average power conversion efficiency (PCE) of 7.6% and a maximum of 8.1% were obtained. The simple processability using common solvents gives Sn(SCN)${}_2$ a distinct advantage over the more well-known copper(I) thiocyanate (CuSCN). The electronic and optical properties of Sn(SCN)${}_2$ make it interesting for applications in large-area electronic devices.

Accepted version. Article has been revised based on peer review comments. Photoelectron spectroscopy result (Fig. 4) after ion etching has been removed as it was determined that the etching depth was not sufficient and replaced with data of two different thicknesses (50 and 90 nm) of the bulk-heterojunction layer. The discussion on band-bending of version 1 has been amended