A Novel Thiophene-fused Ending Group Enabling an Excellent Small Molecule Acceptor for High-performance Fullerene-free Polymer Solar Cells with 11.8% Efficiency

TL;DR

This paper introduces a new small molecule acceptor with a thiophene-fused group, achieving record-high efficiencies in fullerene-free polymer solar cells by enhancing electronic structure and material interactions.

Contribution

The study presents a novel thiophene-fused acceptor, ITCPTC, with significantly improved performance in PSCs, surpassing previous efficiency benchmarks and providing insights into structure-performance relationships.

Findings

Achieved a PCE of 11.8% with ITCPTC-based PSCs.

Enhanced fill factor of 0.751 in the devices.

Structural modifications improve electronic properties and crystallization.

Abstract

In this article, we designed and synthesized a novel small molecule acceptor of ITCPTC with thiophene-fused ending group by employing a new active methylene precursor of CPTCN. The ITCPTC based polymer solar cells with PBT1-EH as donor achieved very high PCEs of up to 11.8% with a remarkably enhanced fill factor (FF) of 0.751, a near 20% boost in PCE with respect to the ITIC based control device. These values are among the highest PCEs and FFs for PSCs. In the whole study, we made contrasts with ITIC to understand the reasons of excellent performance of ITCPTC-based PSCs through various measurements, such as GIWAXS and RSoXS. We revealed that the simple modification of ITIC into ITCPTC not only change the material electronic structure, but also mediate the material interactions and crystallization, which contribute together to the excellent performance of ITCPTC based PSCs.