Impacts of Mn ion in ZnSe passivation on electronic band structure for high efficiency CdS/CdSe quantum dot solar cells

Abstract

Surface passivation in quantum dot-sensitized solar cells (QDSSCs) plays a very important role in preventing surface charge recombination and thus enhancing the power conversion efficiency (PCE). ZnSe passivation with dopant in CdS/CdSe co-sensitized QDSSCs has been demonstrated as an effective way to improve the PCE. In the present study, a series of characterizations revealed that a Mn-doped ZnSe passivation layer can not only reduce surface charge recombination, but also enhance light harvesting. By means of density functional theory calculation along with a systematic study of electronic band structure, it has been found that the valence band of ZnSe moves upward on Mn-ion doping which leads to acceleration of charge separation and broader light absorption range. The impact of the Mn ion on charge recombination and light harvesting has been interpreted reasonably and the PCE of CdS/CdSe co-sensitized QDSSCs with Mn-doped ZnSe passivation layer is as high as 6.46%, which is 1.5 times that of the solar cell without the passivation layer.

Colloidal Synthesis and Characterization of Molybdenum Chalcogenide Quantum Dots Using a Two-Source Precursor Pathway for Photovoltaic Applications

“…MoS 2 exhibited the lowest PCE; this was due to the nanoparticles having a higher charge transfer resistance, which resulted in the limitation of electron transfer, subsequently resulting in low electron–hole recombination, hence, in limited efficiency [ 22 ]. Low efficiency might be due to the increased surface area and thickness on the photoanode which results in charge transfer resistance [ 23 , 24 ]. Furthermore, according to the chemical composition of the samples, the fill factor (FF) was used to determine the quality of the fabricated QDSSCs.…”

Enhanced performance of CdS/CdSe quantum dot-sensitized solar cells by long-persistence phosphors structural layer

“…Finally, the samples were calcined at 500°C for 30 min to eliminate excess ingredients. QDs of CdS and CdSe were prepared according to our previous processes [40].…”

“…Solar cells were assembled by covering the quantum dotsensitized photoanode with a piece of brass with Cu 2 S film as counter electrode. Polysulfide electrolyte was permeated into the assembly as electrolyte [40]. The electrolyte solution in this research was composed of 1 mol L −1 of S and 1 mol L −1 of Na 2 S•9H 2 O in deionized (DI) water at a temperature of 50°C for 60 min.…”

Functionalized polyurethane composite gel electrolyte with cosensitized photoanode for higher solar cell efficiency using a passivation layer

“…Quantum dot solar cells have attracted attention in the modern era because of their low production cost, easy fabrication process and acceptable power conversion efficiency. The inorganic QDs have lot more advantages as compared to dye molecules: (1) high extinction coefficient; 13,14 (2) generation of multiple excitons through single-photon absorption; 15 (3) tuneable band gap; 16 and (4) high photostability corresponding to water and oxygen. 17,18 The maximum theoretical power conversion efficiency of these devices is in order of 44%.…”

“…5,19,20 The surface passivation layer usually enhance the performance of QDSSCs, 21 and this layer can form a uniform barrier layer to separate the photoanode with QDs and electrolytes as well as repair the surface defects of the QDs. 16 Well designed passivation can reduce the electron recombination effectively and the layer promotes the separation process of electrons and holes. 22,23 The higher value of the conduction band edge of ZnS as compared to that of CdS/CdSe helps inhibit the transfer of electrons from the conduction band of QDs to LUMO levels of the electrolytes, and hence, usually used as a passivation layer.…”