The Quantum Dot Sensitized Solar Cells (QDSSCs) using Pt as its counter electrode and poly-sulfide redox shuttle have problems on the low QD’s regeneration speed and high over poten-tial. Sulfur compounds induce a poisoning effect because it was chemisorbed onto the Pt sur-face. It leads to poor charge transfer rate (Sn2-+e-→nS2) at the counter electrode and high over potential for the reduction reaction. The Cu2S was proposed as an ideal counter electrode ma-terials for higher performance QDSSCs due to their higher electrical catalytic activity and stabil-ity. In this study, Cu2S nanocrystals (NCs) are proposed as counter electrode. At the result of, the efficiency of QDSSCs using Cu2S NCs as counter electrode is 0.2% higher than that of using the Pt counter electrode. In addition, The rate of reduction of the Cu2S NCs capped with or-ganic ligands replaced with Na2S (Inorganic) ligands lead to significantly increase. It is demon-strated that the rate of reduction process with Na2S_capped Cu2S NCs counter electrode was more 3 times higher than that of organic_ capped Cu2S NCs counter electrode. Electrochemical impedance spectra (EIS) also confirmed much less resistance by using Na2S capped counter electrode. Finally, we also studied on the effects of nanomaterials and surface modification on the operation of QDSSCs using photoanode materials like CdSe which synthesized by SILAR and hot-temperature injection method. ⓒ 2014 DGIST
Table Of Contents
1. Introduction 1-- 2. Overview solar energy 5-- 3. Theoretical back ground 10-- 3.1 Quantum Dots 10-- 3.1.1 The definition of Quantum Dots 10-- 3.1.2 The classification of QDs synthesis 12-- 3.2 Quantum Dot Sensitized Solar Cells (QDSSCs) 13-- 3.2.1 Basic components of the QDSSCs 13-- 3.2.2 Operation of the QDSSCs 18-- 4. Experimental section 23-- 4.1 Synthesis of colloidal QDs 23-- 4.1.1 Synthesis of CdSe nano crystals for sensitizer 23-- 4.1.2 Synthesis of Cu2S nano crystals on counter electrode 24-- 4.2 QDs deposition on photo electrode 25-- 4.2.1 In-Situ route 25-- 4.2.2 Ex-situ route 25-- 4.3 Fabrication and assembly of QDSSCs 26-- 4.3.1 Fabrication of TiO2 photo electrode 26-- 4.3.2 Fabrication of counter electrode 28-- 4.3.3 Assembly of QDSSCs 29-- 5. Result and discussion 30-- 5.1 Characterization of QDs and QDSSCs 30-- 5.1.1 Optical characterization of QDs 31-- 5.1.2 Characterization of photovoltaic performance of QDSCs 32-- 5.2 The effects of counter electrodes on the QDSSCs performance 34-- 5.3 The study of electrochemical characterization 36-- 6. Conclusions 46-- References 47-- Summary 51