Aqueous-Processed Polymer/Nanocrystal Bulk Heterojunction Solar Cells

The exhaust of fossil energy such as coal, petroleum, and natural gas, etc., is inevitable along with continuous exploition by human beings. Consequently, the consumption of primary energy discharges increased quantity of CO2 and aggravated the Greenhouse Effect, which affect the living environment. The solar is the most popular candidate as an infinite and clean energy. Conservative estimate, the solar energy will directly replaces billions of tons of fossil energy within the 22 nd century. The solar cells, one of the most primary approaches obtaining energy from the sun, are semiconductive thin film devices which convert sunlight into electric energy. Since half century of the invention of solar cells, there have been three generations of solar cells, which called monocrystalline/polycrystalline silicon solar cells, thin film solar cells, and solution-processed, low-cost, high-performance, flexible solar cells. As a member of the third generation solar cells, aqueous-processed polymer/nanocrystal(NC) solar cells draw much attention due to its property of nontoxic solvent, and its increasing performance broaden the space of industrial production. In this thesis, we mainly focus on two works about the aqueous polymer/NC solar cells:(1) High-efficiency aqueous-processed hybrid solar cells with an enormous Herschel infrared contribution. We combined Cd0.75Hg0.25 Te NC with conjugated polymer PBTPV with high charge-carrier-mobility and successfully fabricated hybrid solar cells(HSC) with NIR contribution. The matching energy level between layers ensured dissociation of charges. Annealing process promoted the growth of NC and the elimination of tetrahydrothiophene, which guaranteed the formation of interpenetration network and efficient charge-carrier transport. The power conversion efficiency(PCE) reached 2.7% and the contribution of NIR region attained 15.04%. At that time, this solar cell presents the highest PCE among HSCs based on CdxHg1-xTe NC and the highest NIR contribution among aqueous-processed HSCs.(2) Aqueous-processed colloidal nanocrystal solar cell doped with insulating polymer. We introduced insulating polymer polyvinyl alcohol(PVA) into water-soluble Cd Te NC and obtained solar cell with PCE of 4.32%, the PCE of the pure Cd Te solar cell is 3.63% under the same conditions. After a series of characterizations, we concluded that the introduction of PVA filled the voids among Cd Te NC, as a consequence, the leakage current and recombination were avoided after evaporating of electrode materials, result in enlarged shunt resistance and enhanced performance. In addition, the researches of insulating polymer in HSC lead to deeper understand of the conjugated polymer.