Semiconductor nanochemistry and hybrid polymer photovoltaics ; Halbleiter Nanochemie und hybrid-polimere Solarzellen

The dissertation focuses on the synthesis, mechanism, and structural stability of semiconducting nanoparticles as well as on the development of new hybrid polymeric photovoltaic devices based on nanoparticle/polymer composites. A series of experiments was performed where highly monodisperse nanoparticles of CdSe, CdTe, and InP were synthesized via high temperature organometallic routes. The prepared nanoparticles were characterized by powder XRD, TEM, CV, AFM, HRTEM, EDX, XPS, absorption, and photoluminescence spectroscopy. The first solar cells were produced based on CdTe nanoparticle - polymer composites. CdSe is an important material used for a large number of applications like solar cells, LEDs, biological sensors, catalysts etc. However, the reported synthesis methods for CdSe nanoparticles were based on dimethyl cadmium as Cd source, which is explosive and pyrophoric in nature. In the present work, new high temperature organometallic synthetic methods were developed for the production of good quality CdSe nanoparticles using non pyrophoric cadmium naphthenate and cadmium stearate. A series of surfactants was tried for synthesizing these nanoparticles starting from TOPO to a series of amines. Synthesis of CdSe of various morphologies viz. dots, rods, and various intermediate morphologies were achieved. A detailed mechanistic investigation was carried out for the factors governing the shape control of these nanoparticles. A new theory based on stericity of surfactants for the growth of these nanoparticles was proposed. The results suggest that the surfactant has dominant influence on deciding the morphology of resulting nanoparticles. CdTe nanoparticles can be a key material for polymer photovoltaic devices due to its absorption in the NIR region. However the synthesis of CdTe nanoparticles is not as advanced as CdSe, and the first step for realization of such a cell should be to develop new synthetic strategy for a high quality of CdTe nanoparticles. CdTe nanoparticles of high quality were synthesized using ...