Research on Colloidal Quantum Dot Solar Cell using Selective Ligand Exchange Process

Abstract

Colloidal quantum dot solar cells (CQDSCs) have been investigated in this research. The aim of this research is to develop high-efficiency solar cells. The theoretical limit of energy conversion efficiency of CQDSCs is approximately 45% while 30% is the theoretical limit of single junction crystalline silicon solar cells, which have been mainstream device in photovoltaic market. The CQDSCs of this research are fabricated using zinc oxide (ZnO) nanoparticles and lead sulfide (PbS) or lead selenide (PbSe) colloidal quantum dots (CQDs). The ZnO layer and quantum dot layer are made in room temperature using spin coating and dip coating, respectively. The CQDSCs consist of front electrode made of indium tin oxide (ITO), electron transport layer made of (ZnO), quantum dot layer (PbS or PbSe), and rear electrode. The experimental data of this research were analyzed using the design of experiment method, which revealed strong impact of ligand that covers the surface of CQDs on electrical properties of CQDSCs and uniformity of QD layer. The concentration of 1,2-ethane dithiol (EDT) ligands in ligand exchange process of CQDs needs to be precisely controlled. The open circuit voltage (Voc) is improved by selective ligand exchange method, which is slight and simple adjustment in ligand exchange process under low-EDT process condition. The maximum Voc exceeded 700mV.