Effective Strategy to Improve Contact Selectivity in Organic Solar Cells

Abstract

Improving the contact selectivity is an effective approach to reduce the non-radiative recombination voltage loss caused by charge carrier diffusion in organic solar cells. A surface modification strategy based on the use of the fullerene-selective solvent 1,8-diiodooctane (DIO) is proposed to improve the contact selectivity of organic solar cells. We observe that the fullerene molecules in the binary polymer− fullerene active layers or the ternary active layers containing both fullerene and nonfullerene acceptors are extracted to the surface after the DIO treatment. As a result, a dense fullerene layer, highly selective for electrons, is created at the cathode interface of the solar cell. The increased cathode selectivity gives rise to reduced diffusion loss of charge carriers, suppressed non-radiative recombination voltage loss, increased opencircuit voltage, and thus, the improved photovoltaic performance of the solar cell.

Side-chain engineering improves molecular stacking and miscibility for efficient fullerene organic solar cells

“…From the TEM and AFM phase images During film formation, the fullerene derivative will usually aggregate into clusters and enrich at the bottom of the film due to its high surface energy. After DIO treatment, the fullerene molecules could be extracted to the surface and blended with polymers, 48 thus resulting in smaller and continuous regions on the surface. Moreover, the degree of extraction of fullerene is related to DIO concentration, and the optimal DIO concentration for PPSBTz-Me is more than that for PTSBTz-Me.…”

Novel Beta-Functionalized Porphyrins Approaching 11% Efficiency for Organic Solar Cells

“…The surface morphologies of the blend films were investigated by atomic force microscopy (AFM). As shown in Figure 5, the DIO + TA + SVA-treated films showed enlarged surface root-mean-square (RMS) roughness compared with the as-cast films, which may be ascribed to the fact that the postprocessing treatments promoted the recrystallization of the molecules to form donor-enriched and acceptor-enriched regions, 52 which was…”