Synthesis and applications of low‐bandgap conjugated polymers containing phenothiazine donor and various benzodiazole acceptors for polymer solar cells

Abstract

A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (M n ) in the range of 3.85À5.13 Â 10 4 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300À750 nm with optical bandgaps of 1.80À1.93 eV. Both the HOMO energy level (À5.38 to À5.47 eV) and LUMO energy level (À3.47 to À3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm 2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) or [6,6]-phenyl-C 71butyric acid methyl ester (PC 71 BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC 71 BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (V oc ) value of 0.75 V, a short-circuit current (J sc ) value of 4.60 mA/cm 2 , and a fill factor (FF) value of 35.0% were achieved. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4823][4824][4825][4826][4827][4828][4829][4830][4831][4832][4833][4834] 2010

Synthesis and photovoltaic characterization of D/A structure compound based on N-substituted phenothiazine and benzothiadiazole

“…Moreover, the UV spectrum of P2 was divided into two peaks. The peak absorbing at 300-400 nm is formed because of a delocalized p-p* transition at the polymer chain, and the peak absorbing at 450-650 nm is induced from a localized transition at the state of charge transfer between the donor (phenothiazine unit) and acceptor (benzothiadiazole unit) [46]. Fig.…”

“…MgSO 4 was added to the collected organic layer and it was kept overnight. The solvent was removed through vacuum evaporation and then refined by using column chromatography (hexane/MC = 7/3) [45,46] 1.0 equiv. monomer 3 diluted in THF was put in a 2-neck flask and stirred for about 20 min at À78 8C.…”

“…Among donor materials, phenothiazine has a tricyclic structure including nitrogen and sulfur atoms with abundant electrons; phenothiazine derivatives have HOMO levels of À5.1 to À5.3 eV and an open circuit voltage (V OC ) of 0.71-0.79 V [34][35][36][37][38]. Moreover, phenothiazine leads to the generation of radical cations as a result of oxidation of electrons, and when oxidation proceeds to the next stage, dications will form.…”

Synthesis and photovoltaic properties of conjugated copolymers bearing planar acenaphtho[1,2-b]quinoxaline moiety with deep HOMO level

“…Polymer solar cells (PSCs) have attracted enormous attention due to their high technological potential for low cost, light weight, flexible, and large area photovoltaic application by facile ink-jet or roll-to-roll solution processes [1][2][3][4][5], while the concept of bulk heterojunction (BHJ) structure is commonly employed in PSCs to render bicontinuous interpenetrating network [6][7][8][9], and consequently afford better power conversion efficiencies (PCEs). After years of great research efforts, the PCEs of BHJ PSCs have been enhanced to [7 % [10, 11].…”

Synthesis, Photovoltaic Properties and Side-chain Effect of Copolymer Containing Phenothiazine and 2,1,3-Benzothiadiazole

“…They are also characterized by electrical and thermal stability, with outstanding electro-optical characteristics in the device [16][17][18]. In this study, phenothiazine was used as the electron donor, with benzothiadiazole of a very strong electron affinity as the electron acceptor, with thiophene rich in electrons connected to each terminal to increase the effective π-conjugation length, thereby designing a basic molecular structure that gives the polymer a low band-gap.…”