Preparation Of Zinc Oxide Quantum Dots Modified By Polyethylene Glycol And Their Photovoltaic Application

Organic-inorganic hybrid solar cell is a new type of solar cell, it combines thehole transport capability of conjugated organic materials and electron transfercapabilities of inorganic materials. Organic-inorganic hybrid solar cell can basicallybe achieved by liquid-processing and its material can be obtained from wide rangeof sources. But the property of organic-inorganic hybrid solar cells is influenced bymany factors, such as the choice of materials, device structure design, process routeoptimization, which needs more research to improve device efficiency. The excitonbinding energy of general inorganic materials is low, which cannot make aneffective carrier transmission. ZnO has great research value and applicationprospects due to its high electron affinity, large exciton binding energy, highelectron mobility. Moreover, the synthesis procedure of ZnO is very simple and itsreactants can be obtained from wide variety of sources, so we choose ZnO quantumdots as a hybrid solar cell receptor material in order to get a better photoelectricconversion performance of organic-inorganic hybrid solar cells.ZnO quantum dots are prepared by sol-gel method and optimized by changingits process parameters, then the surface modifier PEG-2000is added to the solutionto modify the surface of ZnO quantum dots. Then we test and analysis the structureand morphology of ZnO quantum dots through a series of test methods, such asUV-Vis, XRD, SEM, TEM, PL, TGA, etc.. When the molar ratio of Zn(Ac)2·2H2Owith KOH is1:1.7, and the concentration of Zn(Ac)2·2H2O is0.1mol·L-1, pure ZnOquantum dots with small size (9.5nm) and well size stability are obtained. But theZnO quantum dots synthesized without any surface modifier has many surfacedefects, which is more tending to agglomerate because of its high surface activityenergy. After PEG-2000modifier is added, the intensity of ZnO quantum dotsemitting defect states decreased with the increasing amount of PEG. When adding0.2g PEG surface modifier, a smaller size (7.5nm) ZnO quantum dot can beachieved with better dimensional stability and more uniform dispersion.The performance of ZnO/P3HT hybrid solar cell demonstrates that the surfacemorphology of the active layer is affected by the proportion of ZnO and interfacialdefects. By changing the content of ZnO and surface modifier, the surfacemorphology of active layer is optimized, and a increased shunt resistor to slow downthe device leakage situation. The efficiency of the device can be up to0.12%through the optimization of ZnO content of33vol.%. Through PEG modificationcan effectively improve device performance, when the PEG fraction was4.6wt.%, the circuit current, open circuit voltage and fill factor improve for8.3%,69.7%and27.8%compared to the device without PEG modification, respectively. Thephotoelectric conversion efficiency reaches0.46%.