Embedded indium-tin-oxide nanoelectrodes for efficiency and lifetime enhancement of polymer-based solar cells

Abstract

In this paper, distinctive indium-tin-oxide (ITO) nanorods are employed to serve as buried electrodes for polymer-based solar cells. The embedded nanoelectrodes allow three-dimensional conducting pathways for low-mobility holes, offering a highly scaffolded cell architecture in addition to bulk heterojunctions. As a result, the power conversion efficiency of a polymer cell with ITO nanoelectrodes is increased to about 3.4% and 4.4% under one-sun and five-sun illumination conditions, respectively, representing an enhancement factor of up to ∼10% and 36% compared to a conventional counterpart. Also, the corresponding device lifetime is prolonged twice as much to about 110 min under five-sun illumination.

Indium tin oxide nanowires growth by dc sputtering

“…The branches are also single crystalline and exhibit same lattice spacings and diffraction patterns as the nanowire backbone. Furthermore, no segregation into core-shell structures was observed in both branches and backbone nanowires, unlike the ITO nanorods grown by e-beam deposition [6].…”

“…However, the lack of catalyst does not necessarily exclude the possibility of vapor-liquidsolid (VLS) growth mechanism. It was proposed that the growth mechanism of ITO nanorods by e-beam deposition is self-catalytic VLS growth [6,13]. Metals with low melting point can easily form droplets for self-catalyzed VLS growth of the nanowires [17], so that it is possible that the growth mechanism is indeed self-catalyzed VLS.…”

“…On the other hand, low temperature methods like chemical synthesis [5] result in free-standing nanostructures instead of nanorod/nanowire arrays/networks on the substrate. In some cases, the use of templates was needed for the ITO nanostructure growth [7,11], while reports on the ITO nanorod/nanowire growth using conventional techniques such as e-beam deposition [6,13] and sputtering [9] have been scarce. While e-beam deposition was performed at oblique incidence [6,13], dc sputtering deposition was simpler, but it resulted in relatively low density of ITO "whiskers" with diameters 10-20 nm and lengths 500 nm-1 µm [9].…”

“…Growth of ITO nanostructures using different methods has been reported [4][5][6][7][8][9][10][11][12][13][14][15][16], such as chemical vapor deposition [4,8,10,14,15], chemical synthesis [5], oblique-incidence electron-beam (ebeam) deposition [6,13], sol electrophoresis [7], sputtering [9,11], and thermal treatment [12]. Some of these methods, such as chemical vapor deposition [4,8,10,14,15] and thermal treatment [12], require a high growth temperature and thus would not be suitable for growth on glass substrates, which are of interest for low cost optoelectronic device applications.…”

“…Although ITO used in practical applications is mainly in the thin film form, there is considerable interest in ITO nanostructures [4][5][6][7][8][9][10][11][12][13][14][15][16], since they can result in very low resistivity [4], as well as enable improved performance of solar cells due to improved charge collection [6]. Growth of ITO nanostructures using different methods has been reported [4][5][6][7][8][9][10][11][12][13][14][15][16], such as chemical vapor deposition [4,8,10,14,15], chemical synthesis [5], oblique-incidence electron-beam (ebeam) deposition [6,13], sol electrophoresis [7], sputtering [9,11], and thermal treatment [12].…”