Development of Polymer Solar Cell System Based on Polymer/Nanocrystal Hybrid and Incorporation of Nanocrystals into Polymer Solar Cell as Additives
Date Issued
2010
Date
2010
Author(s)
Liao, Hsueh-Chung
Abstract
Polymer photovoltaic devices have attracted considerable interest over the past decade owing to the advantages of low-cost, low weight, solution fabrication process, large area and flexibility. The hybrid materials made from conducting polymers and inorganic semiconducting nanocrystals have potential application in solar cell due to their physical stability. In the first part and second part of our study, we have tried to develop new systems of polymer solar cell based on either P3HT / Bi2S3 nanorods or P3HT / Cu2S nanoparticles hybrid. Nanocrystals of Bi2S3 and Cu2S are environmental friendly and low cost. Both nanocrystals have low band gap (lower than 1.8 eV) which show potentials in sun light harvesting. The synthesis and characterization of Bi2S3 nanorods and Cu2S nanoparticles were conducted. Additionally, the properties of hybrid films of P3HT / Bi2S3 nanorods or P3HT / Cu2S nanoparticles were performed. TypeⅡ band alignment between P3HT and low band gap nanocrystals gives chances for charge separation at the interfaces. The photovoltaic devices based on P3HT / Bi2S3 and P3HT / Cu2S hybrid exhibit power conversion efficiency of 0.06 % and 0.1% respectively under AM 1.5, 100 mW/cm2 illumination.
In the third part of this research, we incorporated Cu2S nanoparticles as an additive to improve the power conversion efficiency of P3HT / PCBM system. A 16 % increase in power conversion efficiency (from 3.7 % to 4.3 %) has been achieved by incorporating 0.05 mg ml-1 Cu2S nanoparticles in the P3HT / PCBM active layer under proper thermal treatment. The additive induced morphology variations of active layer were analyzed by AFM and grazing incidence X-ray diffraction. The results reveal the Cu2S nanoparticles hinder the growth of PCBM clusters and compress the crystallization of P3HT during thermal treatment. The smaller crystal dimension of P3HT and reduced size of PCBM clusters result in finer structures, larger interfaces, and closer interconnecting between P3HT and PCBM which enhance the power conversion efficiency. Other nanoparticles such as CdSe with similar size to Cu2S also lead to the similar effect. We therefore conclude that the incorporation of adequate amount of nanoparticles in the active layer is an effective strategy to improve the performance of P3HT / PCBM solar cells.
Subjects
nanoparticle
conducting polymer
solar cell
additive
SDGs
Type
thesis
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