Showing papers by "Chunyan Yang published in 2020"

Non-toxic green food additive enables efficient polymer solar cells through adjusting the phase composition distribution and boosting charge transport

Abstract: Solvent additives play an important role in optimizing the morphology of the photoactive layer and improving the photovoltaic performance of polymer solar cells (PSCs). However, the toxicity of common additives to the environment limits their further application in photovoltaic cells. Herein, a non-toxic green food additive, benzyl salicylate (BS), was introduced as a novel solvent additive into inverted PSCs based on ITO/ZnO/PTB7-Th:PC71BM/MoO3/Ag. Subsequently, the effect of BS on the photovoltaic performance was studied, and the best power conversion efficiency (PCE) of 9.43% was achieved when adding 2% BS into the photoactive layer of PSCs. Furthermore, the PSCs treated by 1–4% BS all exhibited good photovoltaic performance compared to that using 3% DIO (8.56%), which demonstrated that the universality was very strong. In addition, a good solubility for fullerenes was presented on BS like DIO, which was determined by atomic force microscopy and transmission electron microscopy. The water contact angle and time-off flight secondary ion mass spectroscopy results manifested that the good solubility of high-boiling-point additive BS to PC71BM could boost the phase composition distribution at the surface and in the vertical direction. Thus, an efficient route for exciton dissociation and charge transfer could be formed when the PSC was processed via 2% BS, which could also be ascertained by space charge limited current, impedance spectroscopy. The present research findings provide useful information for realizing large-area PSC fabrication, where a greener non-toxic additive is always preferred.

Elevated Photovoltaic Performance in Medium Bandgap Copolymers Composed of Indacenodi-thieno[3,2-b]thiophene and Benzothiadiazole Subunits by Modulating the π-Bridge.

Abstract: Two random conjugated polymers (CPs), namely, PIDTT-TBT and PIDTT-TFBT, in which indacenodithieno[3,2-b]thiophene (IDTT), 3-octylthiophene, and benzothiadiazole (BT) were in turn utilized as electron-donor (D), π-bridge, and electron-acceptor (A) units, were synthesized to comprehensively analyze the impact of reducing thiophene π-bridge and further fluorination on photostability and photovoltaic performance. Meanwhile, the control polymer PIDTT-DTBT with alternating structure was also prepared for comparison. The broadened and enhanced absorption, down-shifted highest occupied molecular orbital energy level (EHOMO), more planar molecular geometry thus enhanced the aggregation in the film state, but insignificant impact on aggregation in solution and photostability were found after both reducing thiophene π-bridge in PIDTT-TBT and further fluorination in PIDTT-TFBT. Consequently, PIDTT-TBT-based device showed 185% increased PCE of 5.84% profited by synergistically elevated VOC, JSC, and FF than those of its counterpart PIDTT-DTBT, and this improvement was chiefly ascribed to the improved absorption, deepened EHOMO, raised μh and more balanced μh/μe, and optimized morphology of photoactive layer. However, the dropped PCE was observed after further fluorination in PIDTT-TFBT, which was mainly restricted by undesired morphology for photoactive layer as a result of strong aggregation even if in the condition of the upshifted VOC. Our preliminary results can demonstrate that modulating the π-bridge in polymer backbone was an effective method with the aim to enhance the performance for solar cell.

Asymmetric push-pull small molecules with auxiliary electron-accepting unit for bulk heterojunction organic solar cells

Abstract: Two small molecular donors (TPA-DPP and TPA-DPP-MDN) were designed with asymmetric push-pull structure, namely, donor-acceptor (D-A) and donor-acceptor-acceptor (D-A-A) systems. They were synthesized and investigated by thermogravimetric analysis, UV–vis spectra, X-ray diffraction, density functional theory (DFT) calculation, electrochemical and the photovoltaic (PV) measurement. The D-A-A architecture (TPA-DPP-MDN) exhibited lower highest occupied molecular orbital (HOMO) of –5.18 eV, narrower optical band gap of 1.52 eV, better thermal stability and higher degree of ordered aggregation than these of the D-A system (TPA-DPP). TPA-DPP-MDN based PV device showed better performance with higher open-circuit voltage (VOC) and short-circuit current density (JSC) than these of TPA-DPP based PV devices due to the low-lying HOMO level and wide spectral absorption range of TPA-DPP-MDN.

Photoelectric properties of low temperature solution-processed three-dimensional Bi2S3 crystals

Abstract: Three-dimensional Bi2S3 with different morphology of flower-like, waxberry like and hydrangea like on the tin-doped indium oxide substrate has been produced from one-step aqueous solution at low temperature (40–70°C) and fixed pH of 0.81 for 24 h. The UV–vis measurement showed that the absorption spectrums of obtained Bi2S3 crystals were occurred blue shift compared to the bulk orthorhombic Bi2S3(1.3 eV). With the increase in temperature, the crystallinity of Bi2S3 films was gradually improved. When the temperature went to 55°C, the best conductivity was obtained.