Large AuAg Alloy Nanoparticles Synthesized in Organic Media Using a One‐Pot Reaction: Their Applications for High‐Performance Bulk Heterojunction Solar Cells

Abstract

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...

Effect of embedded nanoparticle surface chemistry on plasmonic organic photovoltaic devices

“…The use of metal alloy NPs in plasmonic OPV devices has also been reported by Chen et al [37]. Unlike metallic NPs, the characteristic LSPR peak of alloy NPs is tunable through the composition of the alloy.…”

“…The precursors for Au and Ag were gold acetate Au(ac) 3 and AgNO 3 , respectively. These precursors were mixed in proportion to the composition of the alloy NP with several stabilizing ligands, namely trioctylphosphine (TOP), 1,2-dodecanediol (DOD), oleylamine (OAm) and oleic acid (OAc) in octyl ether [37]. The mixture was then heated and refluxed to form the alloy NPs.…”

Morphological Control Agent in Ternary Blend Bulk Heterojunction Solar Cells

“…Inorganic nanocrystals (INCs) can also be included into BHJ film, which is an extensively adopted strategy to enhance device performances [65][66][67][68][69]. The main focus lies on their unique plasma effects for enhancing light scattering path within the thin films.…”

MULTI-PHYSICAL PROPERTIES OF PLASMONIC ORGANIC SOLAR CELLS (Invited Paper)

“…In addition, the near-field plasmon-exciton interactions between Ag NPs and organic molecules in thin-film have been probed experimentally by time-averaged and time-resolved photoluminescence (PL) measurement, which are used to determine the distance dependence of the plasmon-exciton interaction when a transparent, nonemitting spacer layer between the organic emitter and the Ag NPs is applied [99,117]. Besides, large AuAg alloy nanoparticles have been introduced in organic media using a one-plot reaction and enhance the PCE of OSCs by taking advantage of plasmonic light-trapping effect [118]. Theoretically, it is found that Al nanoparticles yield significantly greater enhancement than Ag or Au nanoparticles because much higher plasma frequency of Al nanoparticles ensures a better overlap between plasmon resonance and absorption band of OSCs (Figure 2(f)) [97].…”