Natural dye sensitized solar cell production and determination of photodetector characteristics

In this thesis, both solar cell properties and light detector properties of dye-sensitized photoactive chemical conversion cells have been examined. The structure of dye-sensitized solar cells (DSSC) have been produced by using natural dyes of the same genus but different species Pelargonium Grandiflorum and Pelargonium Hortorum plants. DSSC structures produced with the natural dyes have a recent history in solar cell research and that aims to produce solar cells with environment-friendly materials. The reasons for choosing plants of the same genus but different species are likely to give comparable results with the GC-MS analysis of the plant content and determine the components which affect solar cell yield in natural dye. When GC-MS analyzes and solar cell efficiencies are taken into account, the findings from GC-MS analysis reveal that the gallic acid is a substance of yield enhancer. When the solar cell characteristics are examined by single diode and double diode model, it is observed that gallic acid significantly reduces the series resistance in the photoactive layer, improves the leakage current, ensures the ideality factor of the DSSC about to 1 ideal values and all these parameters have also improved the efficiency of the solar cell. The uses of dye sensitized structures as photodetector have also been examined with the experimental research in this thesis. The photodetector examinations have been performed by comparison with a commercially single-crystal Si (Newport 818-R) photodetector. When the photoreaction measurement is performed with the help of neutral density filters in the range of 34-2.3 W/m2, it has been observed that DSSC photodetector provides about 10 times more output power and higher fill factor compared to high quality c-Si photodetector and the DSSC photodetector has superior characteristics especially for low light intensities. The temperature stability of the produced photodetectors are also examined in the range of 298-373 oK. Another important parameter for photodetectors is the response time. The response times of the DSSCs which have been produced using natural dyes, are examined by transient photocurrent and photovoltage methods. It has been observed that DSSC photodetectors perform a pulse within the first few nanoseconds that originally interacts with light, but it can convert the produced pulse to a continuous flow (d.c.) around ~ 0.1 s. After the perception of the pulse in the nanosecond range, the delay in the d.c. current production in 0.1 s ranking is attributed to the total duration of the redox reactions in the photochemical cell, the catalytic activity processes and the rate of electron transport within the liquid electrolyte during this time. Keywords: Solar Cell, Photodetector, Single Diode Model, Double Diode Model.