Youjun He

6.5% Efficiency of Polymer Solar Cells Based on poly(3‐hexylthiophene) and Indene‐C60 Bisadduct by Device Optimization

A power conversion efficiency of 6.48% was achieved for polymer solar cells based on poly(3-hexylthiophene) (P3HT) as donor and indene-C₆₀ bisadduct (ICBA) as acceptor with an open-circuit voltage of 0.84 V, a short-circuit current of 10.61 mA/cm², and a fill factor of 72.7% under irradiation at AM1.5G, 100 mW/cm² at the optimized conditions of P3HT:ICBA = 1:1 (w/w), solvent annealing and pre-thermal annealing at 150 °C for 10 minutes.

Low Bandgap Polymers by Copolymerization of Thiophene with Benzothiadiazole

Three low bandgap copolymers of thiophene and benzothiadiazole with electron-donating and electron-withdrawing substituents, P1, P2, and P3, have been synthesized by Pd-catalyzed Stille-coupling. Electronic energy levels of the polymers are estimated by cyclic voltammetry. The polymer films show a broad absorption band in the wavelength range from 300 to 750 nm. Among the polymers, the polymer that contains the 5,6-dinitrobenzothiadiazole unit, P3, possesses the smallest bandgap of 1.55 eV calculated from its absorption band-edge at ≈800 nm. With the increase of the electron-withdrawing ability of the substituents on the benzothiadiazole unit, the energy bandgap of the polymers decreased in the order P1u2009>u2009P2u2009>u2009P3. The results indicate that stronger electron-withdrawing substituents on the acceptor unit can effectively decrease the bandgap of the polymers.

Synthesis and photovoltaic properties of D–A copolymers of benzodithiophene and naphtho[2,3-c]thiophene-4,9-dione

Two donor–acceptor (D–A) alternative copolymers of benzodithiophene (BDT) donor unit and an acceptor unit of naphtho[2,3-c]thiophene-4,9-dione (NTDO) with different alkyl side chains, PBDTNTDO-1 and PBDTNTDO-2, were synthesized for application as donor materials in polymer solar cells (PSCs). The copolymers show good solubility in common organic solvents, broad visible absorption from 350 nm to 670 nm, and relatively lower HOMO energy levels at −5.14 eV for PBDTNTDO-1 and −5.19 eV for PBDTNTDO-2. The PSCs based on PBDTNTDO-2 as donor and PC70BM as acceptor demonstrated power conversion efficiency of 1.52% with an open circuit voltage of 0.88 V and a short circuit current of 5.67 mA cm−2, under the illumination of AM1.5, 100 mW cm−2.

Synthesis and photovoltaic properties of alternative copolymers of benzo[1,2-b:4,5-b′]dithiophene and thiophene

Two conjugated polymers containing benzodithiophene (BDT) unit and the unit of thiophene or thieno[3,2-b]thiophene, P(BDT-T) and P(BDT-TT), were synthesized by Pd-catalyzed Stille coupling method. The UV–Vis absorption, thermal, and electrochemical properties of the two polymers were characterized. Photovoltaic properties of the polymers were studied by using the polymers as donor and PC70BM as acceptor with a weight ratio of polymer: PC70BM of 1:1.5. The power conversion efficiencies of the PSC devices based on P(BDT-T) reached 2.05% with an open-circuit voltage of 0.75xa0V, a short-circuit current of 4.5xa0mAxa0cm−2, and a fill factor of 0.61, under the illumination of AM1.5, 100xa0mWxa0cm−2.