Abstract
Due to the high absorption coefficient and modulated band gap of non-fullerene small molecule acceptors (NFAs), photons can be utilized more efficiently in near-infrared (NIR) range. In this report, we highlight a system with a well-known polymer donor (PTB7-Th) blended with a narrow bandgap non-fullerene acceptor (IEICO-4F) as active layer and 1-chloronaphthalene (CN) as the solvent additive. The optimization of the photoactive layer nanomorphology yields short-circuit current density value (Jsc) of 27.3 mA/cm2, one of the highest value in OSCs reported to date, which competes with other types of solution processed solar cells such as perovskite or quantum dot devices. Along with decent open-circuit voltage (0.71V) and fill factor values (66%), a power conversion efficiency of 12.8% is achieved for the champion devices. Grazing incidence wide-angle X-ray scattering (GIWAXS) patterns and resonant soft X-ray scattering (R-SoXS) elucidate that the origin of this high photocurrent is mainly due to increased π-π coherence length of the acceptor, the domain spacing as well as the mean-square composition variation of the blend. Optoelectronic measurements confirm a balanced hole and electron mobility and reduced trap-assisted recombination for the best devices. These findings unveil the relevant solvent processing-nanostructure-electronic properties correlation in low band gap non-fullerene based solar cells, which provide a helpful guide for maximizing photocurrent that can pave the way for high efficiency organic solar cells.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 669-676 |
| Number of pages | 8 |
| Journal | ACS Energy Letters |
| Volume | 3 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jan 23 2018 |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledgements: D. Baran acknowledges KAUST Solar Center Competitive Fund (CCF) for financial support. GIWAXS/R-SoXS measurements and analysis by L. Ye and H. Ade are supported by ONR grant N00141512322 and KAUST’s Center Partnership Fund (No. 3321). X-ray data were acquired at beamlines 7.3.3 and 11.0.1.2 at the Advanced Light Source (ALS) in Berkeley National Lab, which is supported by the U.S. Department of Energy (DE-AC02-05CH11231). Z. Peng, S. Stuard, and I. Angunawela assisted with part of the R-SoXS data acquisition. C. Wang, C. Zhu, A.L.D. Kilcoyne, and E. Schaible are acknowledged for the beamline support. The material (IEICO-4F) was synthesized by H. Yao and J. Hou, which is supported by natural science foundation of china (21325419, 51373181 and 91333204).