Photovoltaic properties and annealing effects of a low bandgap copolymer containing dithienothiophene and benzothiadiazole units

Abstract

Abstract.A conjugated alternating copolymer as the donor material of the active layer in polymer solar cells has been designed and synthesized via Stille coupling reaction. The alternating structure consisted of 3,5-didecanyldithieno[3,2-b:2!,3!-d]thiophene (DDTT) donor unit and 5,6-bis(tetradecyloxy)benzo-2,1,3-thiadiazole (BT) acceptor unit. Since both units have been attached pendant chains, the polymer was soluble in common organic solvents. UV-vis spectrum exhibited a broad absorption band in the range of 270-780 nm and a low bandgap of 1.83 eV. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the polymer were estimated to be -5.10 and -3.27 eV, respectively. Based on the ITO/PEDOT:PSS/PDDTTBT:PCBM/Al device structure, the power conversion efficiency (PCE) under the illumination of AM 1.5 (100 mW/cm 2 ) was 0.127%. The effects of annealing temperature (50-150°C) for 30 min on the device performance were studied. It was found that PCE of 0.292% could be acquired under the annealing condition at 50°C for 30 min. The improved device efficiency under the optimal condition was confirmed by the higher light harvest in UV-vis spectra, the enhanced quenching of photoluminescence (PL) emission, and the improved nanoscale morphology by atomic force microscopy (AFM) examination.

Analysis of the electrical and optical properties of PEDOT:PSS/PVA blends for low-cost and high-performance organic electronic and optoelectronic devices

“…Semiconducting polymers represent a class of electronic materials which have been applied in the development of a large variety of new electronic and optoelectronic devices, including organic light emitting diodes (OLEDs) [1][2][3], organic photovoltaic cells (OPVs) [4][5][6][7], organic field effect transistors (OFETs) [8], transducers for chemical or biochemical analysis [9,10] and many other applications [11,12]. Depending on the device functionality, a different semiconducting property of the active material is more relevant: charge-carrier recombination efficiency for OLEDs, energy conversion efficiency for OPVs and charge-carrier mobility for OFETs, for example.…”

Synthesis and property characterization of two novel side-chain isoindigo copolymers for polymer solar cells

“…After cooled to room temperature, the mixture was poured into water (100 mL) and extracted with dichloromethane. The organic phase was washed with water and dried over anhydrous MgSO 4 . After concentration, the crude product was purified on silica gel chromatography using a petroleum ether/dichloromethane mixture (1/1 by volume) as eluent to afford a yellow liquid (4.49 g, 73.2%).…”

“…Then the mixture was heated to 70°C for 24 h. After cooled to room temperature, the mixture was extracted with CH 2 Cl 2 and washed with water. The organic phase was dried over anhydrous MgSO 4 and the solvent was removed by rotary evaporation. The crude product was purified on silica gel chromatography using petroleum ether as eluent to afford a yellow-green solid (1.03 g, 39.1%).…”

“…Compound 1 (6.00 g, 22.22 mmol) and compound 2 (24.85 g, 66.66 mmol) were dissolved in anhydrous toluene (120 mL) and deoxygenated with nitrogen for 15 min. Pd(PPh 3 ) 4 (230 mg, 0.67 mmol) was then added under nitrogen and the mixture was again flushed with nitrogen for 30 min. Then the reaction mixture was stirred at 110°C for 2 days under nitrogen atmosphere.…”

“…In recent years, polymer solar cells (PSCs) have attracted considerable attention due to their unique advantages, such as low cost, light weight, solution processibility, and flexibility of molecular design [1][2][3]. The bulk heterojunction (BHJ) structure, which is composed of a photoactive blend layer of a conjugated polymer donor and a fullerene derivative acceptor, sandwiched between an anode and a cathode (at least one of them should be transparent), is one of the most successful and useful architectures in PSCs [4][5][6][7][8]. Recently, great advances have been made in the development of high-efficiency photovoltaic materials and device structures, especially in multiple-junction tandem solar cell and ternary solar cells.…”