A tailor-made medium-band gap fluorinated quinoxalinebased conjugated polymer of PBDT-TFQ was designed and synthesized as a donor material for bulk-heterojunction (BHJ) solar cells. This polymer is possessed of an intrachain donor−acceptor architecture and exhibits a broad and strong absorption spectrum across the entire UV−vis region. The introduction of F atoms with high electron affinity to the quinoxaline moiety is effective in further lowering both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of PBDT-TFQ to attain higher open-circuit voltage (V oc ). With an optimized blend ratio of PBDT-TFQ:PC 71 BM (1:1, w/w), a high power conversion efficiency (PCE) of 8.0% was obtained, with a V oc of 0.76 V, a short-circuit current density (J sc ) of 18.2 mA cm −2 , and a fill factor (FF) of 58.1% under AM 1.5G irradiation. The resulting copolymer reveals an outstanding J sc value, arising from the higher hole mobility of PBDT-TFQ, together with the better continuous percolation pathways within the polymer blend for efficient exciton dissociation and charge transport.
bulk heterojunction (BHJ) confi guration has been attracting considerable interest due to their low-cost fabrication, mechanical fl exibility and potential to provide effi cient conversion of solar energy. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] There are a number of challenges on the way to achieve high power conversion effi ciency (PCE) of solar cells. These include the development of low bandgap conjugated polymers with respect to broad light absorption and effi cient charge separation/transportation via controlling the nanostructure of active layer. As a result, several highly effi cient polymers have been reported with high PCE surpassing than 7% to date. [7][8][9] Considering the power conversion processes, including solar light absorption, exciton generation, exciton dissociation, and charge carriers transport, all occur in the active layers. [17][18][19][20][21][22][23][24][25] Therefore, gaining insight into the nanostructure of the active layer and the corresponding morphology, [22][23][24][25] as well as the photovoltaic mechanism, [17][18][19][20][21] is benefi cial to meliorate the PCE of the resulting BHJ solar cells. It is well known that reducing recombination is a linchpin of increasing device effi ciency. [ 22 ] Therefore, decreasing the thickness of the active layer and maximizing its absorption capability to reduce the device resistance and the probability of charge recombination play key roles to improve the device's PCE. From this viewpoint, a remarkable amount of work has been devoted to utilizing metal nanoparticles (NPs) strategies that result from their localized surface plasmon resonance (LSPR) for effi cient light trapping in the active layer in an aim to enhance photon absorption without the need for a thick fi lm. [26][27][28] To date, most studies are focused on single-composition of gold, silver, and copper NPs, which are almost exclusively suspended in aqueous solution. [28][29][30] In comparison, much less systematic experimental study of alloying metal NPs has been performed in photo voltaic performance so far. [ 31 ] More importantly, conjugated polymers are soluble primarily in organic solvents, which are incompatible with aqueous media. This limits the use of these metal NPs in organic photovoltaic devices. Although many of the device geometries have been reported to directly introduce various species of aqueous phase metal NPs in poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) A one-pot synthesis of large size and high quality AuAg alloy nanoparticles (NPs) with well controlled compositions via hot organic media is demonstrated. Amid the synthesis, complexation between trioctylphosphine (TOP) and metal precursors is found, which slows down the rate of nucleation and leads to the growth of large-size AuAg nanoalloys. The wavelength and relative intensities of the resulting plasmon bands are readily fi ne-tuned during the synthetic process using different Au/Ag precursors molar ratios. In the polymer solar cells, a key step in achieving high effi ciency...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.