Organik tabanli güneş pili üretimi ve karakterizasyonu

Organic electronic materials are conjugated solids where both optical absorption and charge transport are dominated by partly delocalised ? and ?* orbitals and differ from inorganic semiconductors in the following important respects. Photogenerated excitations are strongly bound and do not spontaneously dissociate into charge pairs. Charge transport proceeds by hopping between localised states, rather than transport within a band. Absorption coefficients are high so that high optical densities can be achieved. As one-dimensional semiconductors, their electronic and optical properties can be highly anisotropic. This is potentially useful for device design. Due to their above special properties and ease of fabrication and compatibility with flexible substrates, organic materials have long attracted wide spread attention in the field of electronics. Renewable, clean energy sources are gaining importance due to increase demand, cost and failure of conventional energy sources to meet the energy requirements of various sectors. Photovoltaic cells are considered as an important source of renewable energy to solve the world's energy shortage today. Silicon solar cells currently dominate the PV market, as they have demonstrated high power conversion efficiencies (PCE), due to the excellent charge transport properties and environmental stability of high purity silicon. Advantage of Si over other semiconductor devices is due to well developed microelectronics industry which has considerable knowledge of working with Si. This makes Si a better candidate for solar cells as compared to other semiconductor xiii material such as gallium arsenide (GaAs) or germanium (Ge). Currently, inorganic photovoltaic devices perform with higher photoelectric conversion efficiency and stability, than organic photovoltaic (OPV) devices. However, inorganic photovoltaic devices still have deficiencies, such as high manufacturing cost and solid construction, which hampers their application as cheap consumables and flexible electronic products. The methods used to manufacture high efficiency silicon solar cells are costly. Purification techniques used to produce high quality silicon, coupled with high temperature, low throughput manufacturing techniques lead to high energy costs, which is hindering the progress of PV. The search for low cost photovoltaics has led researchers to organic materials as possible candidates. The discovery of organic materials which have both conducting and semiconductor properties has led to new and exciting possibilities in the field of optoelectronic devices. The development of organic photovoltaic devices may play a key role in overcoming the deficiencies of inorganic photovoltaic devices, because they offer several advantages such as: Lower energy and material consumption during the manufacturing process, low cost, low temperature process compatible with flexible substrates, and extremely lightweight. Additionally, organic semiconductors have very high absorption coefficients, which allow very thin films to be used, whilst still absorbing a sufficient portion of the solar spectrum. This reduction in material used, coupled with low cost manufacturing techniques, implies that organic semiconductors have the potential to make a significant impact on the PV market. Hence, OPV devices with these significant advantages have attracted a great deal of attention, forcing researchers to invest a great deal of effort in pursuing higher photoelectric conversion efficiency. With more increase in power conversion efficiency and progress of stability, OSCs could be promising to make cost-effective devices as an alternative to the silicon-based solar cells. Although significant improvement in power conversion efficiency has been obtained, the efficiencies attained so far are still comparatively low and there is scope for further improvement in all three factors that impact power conversion efficiency namely, short-circuit current, open-circuit voltage and fill factor. A general problem in organic electrical devices is the transport of charge carriers at the interfaces electrode/organic material. A variety of interfacial treatments have been applied to both the cathode/organic and the anode/organic interfaces, different more or less thin buffer layers have been placed at these interfaces, resulting in varying degrees of devices improvement in terms of charge exchange. In this thesis, organic and organic/inorganic photovoltaic devices based on solution processed phthalocyanine donor layer, fullerene (C60) and: tris(8- hydroxyquinolinato)aluminium (Alq3) acceptor have been fabricated. For comparison, porous silicon and tin oxide coated glass were used as anode electrode materials and their effects on device characteristics were studied. Porous silicon (PS) was obtained by electrochemical etching of p-type and n-type Si wafers in hyroflouric acid solution at a current density of 15 mA/cm2 , the etching time being varied from from 5 min to 20 min. for both type Si. The electrical properties of the produced photo-voltaic cells under dark and illumination conditions were investigated and different parameters such as open circuit voltage, short circuit current and maximum power efficiency were determined. It was found that the cell parameters depend on the anodization time xiv and the choice of anod electrode material is critical to cell performance. Maximum power conversion efficiency was obtained with the structure of ITO/Alq3/C60/Al. Key words: Organic elektronic, photovoltaic effect, renewable energy, exciton, open circuit voltage, short circuit current