Revealing the Impact of F4‐TCNQ as Additive on Morphology and Performance of High‐Efficiency Nonfullerene Organic Solar Cells
Abstract
Fluorinated molecule 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ) and its derivatives have been used in polymer:fullerene solar cells primarily as a dopant to optimize the electrical properties and device performance. However, the underlying mechanism and generality of how F4‐TCNQ affects device operation and possibly the morphology is poorly understood, particularly for emerging nonfullerene organic solar cells. In this work, the influence of F4‐TCNQ on the blend film morphology and photovoltaic performance of nonfullerene solar cells processed by a single halogen‐free solvent is systematically investigated using a set of morphological and electrical characterizations. In solar cells with a high‐performance polymer:small molecule blend FTAZ:IT‐M, F4‐TCNQ has a negligibly small effect on the molecular packing and surface characteristics, while it clearly affects the electronic properties and mean‐square composition variation of the bulk. In comparison to the control devices with an average power conversion efficiency (PCE) of 11.8%, inclusion of a trace amount of F4‐TCNQ in the active layer has improved device fill factor and current density, which has resulted into a PCE of 12.4%. Further increase in F4‐TCNQ content degrades device performance. This investigation aims at delineating the precise role of F4‐TCNQ in nonfullerene bulk heterojunction films, and thereby establishing a facile approach to fabricate highly optimized nonfullerene solar cells.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 14, 2018
- Source ID
- 10.1002/adfm.201806262
Entities
People
- Abay Gadisa
- Harald Ade
- Jeromy James Rech
- Long Ye
- Qianqian Zhang
- Wei You
- Yuan Xiong
Organizations
- National Science Foundation
- North Carolina State University
- Office of Naval Research
- United States Department of Energy
- University of North Carolina at Chapel Hill