Effects of the Donor Unit on the Formation of Hybrid Layers of Donor-Acceptor Copolymers with Silver Nanoparticles

Abstract

Donor-acceptor (D-A) copolymers containing perylene-3,4,9,10-tetracarboxydiimide (PDI) electron-acceptor (A) units belonging to n-type semiconductors are of interest due to their many potential applications in photonics, particularly for electron-transporting layers in all-polymeric or perovskite solar cells. Combining D-A copolymers and silver nanoparticles (Ag-NPs) can further improve material properties and device performances. Hybrid layers of D-A copolymers containing PDI units and different electron-donor (D) units (9-(2-ethylhexyl)carbazole or 9,9-dioctylfluorene) with Ag-NPs were prepared electrochemically during the reduction of pristine copolymer layers. The formation of hybrid layers with Ag-NP coverage was monitored by in-situ measurement of absorption spectra. The Ag-NP coverage of up to 41% was higher in hybrid layers made of copolymer with 9-(2-ethylhexyl)carbazole D units than in those made of copolymer with 9,9-dioctylfluorene D units. The pristine and hybrid copolymer layers were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy, which proved the formation of hybrid layers with stable Ag-NPs in the metallic state with average diameters <70 nm. The influence of D units on Ag-NP diameters and coverage was revealed.

Donor-Acceptor Copolymers with 9-(2-Ethylhexyl)carbazole or Dibenzothiophene-5,5-dioxide Donor Units and 5,6-Difluorobenzo[c][1,2,5]thiadiazole Acceptor Units for Photonics

“…Non-fullerene small-molecule organic electron acceptors such as ITIC-4F or Y6 (Figure 12) can be used. D-A copolymers with perylene-3,4,9,10-tetracarboxydiimide-based A units and various D units (Figure 12) synthesized and studied in our previous work are suitable as electron acceptors due to their higher electron affinities (3.8-3.9 eV) and other desirable properties [46,47,101]. These n-type polymers could also be used in ternary solar cells together with a second acceptor, such as ITIC-4F or Y6, with higher electron affinities and absorption in the NIR region, improving sunlight harvesting.…”

“…In this work, we have focused on the syntheses and study of two new D-A copolymers possessing the interesting fluorinated benzothiadiazole as an A unit, which is in the center of the 4,7-bis(4 -(2-octyldodecyl)thiophen-2 -yl)-5,6-difluorobenzo[c] [1,2,5]thiadiazole (ODTffBT) building block, and two different D units: 9-(2-ethylhexyl)carbazole (CzEH) and dibenzothiophene-5,5-dioxide (DBSO). Conjugated polymers with carbazole derivatives such as CzEH incorporated in the backbone exhibit interesting photophysical, electroluminescent, and electrochromic properties for photonic applications [45][46][47][48][49]. The CzEH carbazole-based D unit has stronger electron-donating ability compared with DBSO, which has been reported mainly as an A unit in a series of conjugated copolymers based on fluorene or carbazole [50][51][52][53][54][55][56][57].…”