N-Acyldithieno[3,2-b:2′,3′-d]pyrrole-Based Low-Band-Gap Conjugated Polymer Solar Cells with Amine-Modified [6,6]-Phenyl-C61-butyric Acid Ester Cathode Interlayers

Abstract

Efficient low-band-gap polymers are one key component for constructing tandem solar cells with other higher-band-gap materials to harvest wide absorption of the solar spectrum. The N-acyldithieno[3,2-b:2',3'-d]pyrrole (DTP) building block is used for making low-band-gap polymers. It is attractive because of its strong donating ability and relatively low highest-occupied-molecular-orbital level in comparison with the N-alkyl DTP building block. However, additional solubilizing groups on the accepting units are needed for soluble donor-acceptor polymers based on the N-alkanoyl DTP building block. Combining N-benzoyl DTP with a 4,7-dithieno-2,1,3-benzothiadiazole building block, a polymer with a low band gap of 1.44 eV, delivers a high short-circuit current of 17.1 mA/cm(2) and a power conversion efficiency of 3.95%, which are the highest for the devices with DTP-containing materials. Herein, an alcohol-soluble diamine-modified fullerene cathode interfacial layer improved the device efficiency significantly more than the mono-amine analogue.

Recent Advances in Bulk Heterojunction Polymer Solar Cells

“…205,297 Duan et al 299 provide another option because they match the LUMO energy level of commonly used acceptor materials such as PCBM and ICBA, while they feature deep HOMO energy levels which endow them with good hole-blocking properties. Recently, many fullerene-based ESL materials have been developed by attaching polar groups such as phosphoric esters, 302 amines, 303 cationic ammonium, 304 and carboxylic acids 305 to fullerenes. Structures of the fullerene derivatives discussed in this section are summarized in Figure 44.…”

Zwitterionic ammonium and neutral amino molecules as cathode interlayer for inverted polymer solar cells

“…It was proposed that these hydrophilic organic interlayers can recover the lost open-circuit voltage (V oc ) and enhance the electron collection from the acceptor to ITO, because of the built-in field deriving from the interfacial dipole of the interlayer [11,34]. Under the guidance of this theory, several specific functional groups are introduced to alcohol-soluble interface materials, such as ethylene oxide [35], phosphonate [36,37], amino [38][39][40][41][42] and ammonium [43,44]. In our previous study, we have reported a series of alcohol-soluble small molecules including amino and ammonium derivatives, and used them as charge-injection materials for polymer lightemitting diodes (PLEDs) [45].…”

Direct (hetero)arylation polymerization for the synthesis of donor–acceptor conjugated polymers based on N‐benzoyldithieno [3,2‐b:2′,3′‐d]pyrrole and diketopyrrolopyrrole toward organic photovoltaic cell application

“…Although this pioneer study creates great potential in energy level engineering, these strategies still lack the attention of researchers. Chen's group reported organic solar cells based on N ‐acyldithieno[3,2‐b:2′,3′‐d]pyrrole having a low bandgap of 1.44 eV and a short circuit current density ( J sc ) of 17.1 mA cm −2 . More recently, Kesters et al .…”