Crystalline donor–acceptor conjugated polymers for bulk heterojunction photovoltaics

Abstract

Molecular engineering of conjugated polymers for tuning their energy bands is an important process in the quest for highly efficient bulk heterojunction (BHJ) polymer photovoltaic devices. One effective approach is to construct a conjugated polymer by conjugating two chemical units possessing different electron donating (donor) and accepting (acceptor) capabilities. Conjugated copolymers featuring donoracceptor (D/A) subunits are promising materials for solar cell applications because of their tunable energy bands and solubility that can be tailored to the performances of the photovoltaic devices. Under proper processing conditions, the conjugated polymers with rigid and planar D/A segments can undergo self-assembly to form crystalline structures that improve charge carrier mobility and provide better resistance to the permeation of water and oxygen compared to amorphous polymers. Conjugated polymers withD/A structure have been investigated thoroughly over the last few years. In this highlight, we present an overview of recent developments in BHJ organic photovoltaics employing D/A crystalline copolymers as active layer materials for photon-to-electron conversion, with particular emphasis on crystalline D/A polymers featuring newly developed acceptor structures, including thieno [3,4-c]pyrrole-4,6-dione, diketo-pyrrole-pyrrole, bithiazole, thiazolothiazole and thieno[3,2-b]thiophene moieties, and conclude with future perspectives.

Synthesis and organic field effect transistor properties of isoindigo/DPP-based polymers containing a thermolabile group

“…To date, the donor-acceptor (D-A) system, the alternative linkage between electron-rich and electron-decient aromatic units, is one of the important protocols to design low bandgap electron donating materials in organic photovoltaic cells (OPVs), 4 as well as high mobility CPs for OFETs. [5][6][7] Careful design and the matching between the selected donor and acceptor molecular units help us to tune the HOMO and LUMO energy levels as well as the bandgap of synthesized CPs, owing to the HOMO and LUMO energy levels being centered on the donor and acceptor moieties, respectively.…”

Modified structure of two-dimensional polythiophene derivatives by incorporating electron-deficient units into terthiophene-vinylene conjugated side chains and the polymer backbone: synthesis, optoelectronic and self-assembly properties, and photovoltaic application

“…42 The hole mobilities of polymers were measured in a hole-only device (ITO/PEDOT:PSS/ pristine polymer/Au) using the space-charge-limited current (SCLC) method. Fig.…”

Solubilized 5,6-bis(octyloxy)benzoxadiazole as a versatile acceptor block for designing novel (-X-DADAD-)n and (-X-DADADAD-)n electron donor copolymers for bulk heterojunction organic solar cells

“…Vast majority of highly efficient photoactive materials belong to the push-pull group of polymers which comprise electron-rich (donor) and electron-deficient (acceptor) units in their molecular backbone [7][8][9][10][11]. An appropriate combination of donor and acceptor blocks enables tuning the energy levels and energy band gaps of polymers providing solar cells with enhanced open circuit voltage (V OC ) and short circuit current density (J SC ).…”