Electrochemically Guided Photovoltaic Devices: A Photocurrent Study of the Charge Transfer Directionality between CdTe and CdSe Nanoparticles

Abstract

This work reports on the energy level alignment and charge transfer in organized assemblies of CdTe and CdSe nanoparticles (NPs), for both electrochemical systems and in solid-state photovoltaic devices. This work shows how control over the energy level alignment, by manipulation of the size and surface ligands of the CdTe and CdSe NPs, can be combined with control over the NPs spatial arrangement, either by sequential self-assembly onto a Au working electrode of an electrochemical cell or spin-coating onto an ITO substrate of a photovoltaic device, to facilitate photoinduced charge separation (photocurrent). By properly arranging the spatial and energetic hierarchy of the assemblies, the charge transfer direction and its efficiency can be optimized.

Improving Solar Cell Performance Using Quantum Dot Triad Charge-Separation Engines

“…Type II band alignment also slows back electron transfer compared to the case for type I band alignment. 13,17,21,22 For a CdSe QD electron acceptor, the energy difference between its conduction band and the valence band of a CdTe QD is more favorable for charge recombination in type II QDs than for type I QDs because the nonradiative charge recombination is disfavored by the Marcus inverted effect in type I heterojunctions. 23,24 Consequently, charge recombination is believed to limit the power conversion efficiency of QD solar cells 25−27 and can dominate over the device advantages of type II architectures, which arise from the large forward charge transfer rates and the small differences between electron and hole transfer rate constants.…”

In situ fabrication of Bi2S3 nanocrystal film for photovoltaic devices

“…However, there are several crucial deficiencies existing in such organic/inorganic hybrid solar cells. One is the use of toxic elements, such as Cd [7], Pb [8], or toxic solvents, which should be eventually replaced. Another is the bad compatibility between inorganic nanocrystals (NCs) and transparent conducting substrate.…”

Three Synthetic Routes to a Commercial N3 Dye

“…Solar energy is one of the most promising future energy which referred as "photovoltaic cells" (PV) [1]. However, the first generation of PV is an inorganic thin-film photovoltaic devices, i.e., CdTe [2] and CuIn(As)Se [3], which contain highly toxic and expensive materials. For that reason, the second generation of solar converters called "dye-sensitized solar cells (DSCs)" has been developed [4], [5].…”

“…For that reason, the second generation of solar converters called "dye-sensitized solar cells (DSCs)" has been developed [4], [5]. This solar cell architecture has emerged as a promising candidate for practical photovoltaic applications by virtue of their low manufacturing costs and good conversion efficiencies [1], [2]. Numerous sensitizers have been prepared and their performance has been tested.…”

“…Numerous sensitizers have been prepared and their performance has been tested. DSSCs with power conversion efficiencies over 10% under AM 1.5 irradiation were initially demonstrated using prototype cis -di(thiocyanato)-bis[2,2′-bipyridyl-4,4′-dicarboxylic acid] ruthenium(II) (N3), its bis-tetrabutylammonium (TBA) salt counterpart (N719), or the black dye [tri(thiocyanato)-(4,4′,4′′-[2,2′:6′,2′′-terpyridine] tricarboxylic acid]ruthenium(II) as a sensitizers in combination with thicker titania films (>12-15 μm) and volatile electrolytes [2]. In DSSCs, the sensitizer is one of the critical components because it absorbs sunlight and induces intramolecular charge transfer from the ancillary to the anchoring ligand with subsequent electron injection to the TiO 2 via the carboxylic acid groups.…”