Materials And Devices Research Of P3HT-TiO₂ Heterojunction Solar Cells

Since entering the new century, the traditional fossil fuels are depleted. We need to find a new renewable energy sources urgently to solve the energy crisis. People have taken notice of solar energy that is over 99% of total energy on the earth, and solar energy has so many merits that many scientists have focused on them like as widest distribution and convenient acquisition, innocuous to persons and unpolluted to environment, extremely excessive amount, et al.The traditional silicon-based solar cells have been on the commercial applications in the small-scale devices and the solar energy collection efficiency reached 24%. But the production process is complex and the mature technologies make the photoelectric conversion efficiency achieve maximum, which make it difficult to ameliorate. In addition, the material itself is not conducive to reduce costs. All of that limit its large-scale civilian. In the exploration of new materials, organic conductive polymer gradually becomes the hotspot of the research. The organic synthesis process of the organic polymer is simple and most of the materials have been achieving industrialization. therefore, it has a low cost , easy to process, makes film with a variety of methods , can control the film thickness in the molecular direction of growth and modified its physical easily.The organic conductive polymer such as polyaniline(Pan), polypyrrole( PPY), polythiophene(PTh), and polyphenylacetylene(PPV) is a hot research currently, and has replaced inorganic materials in many areas. Polythiophene are an important representative class of conjugated polymers that form some of the most environmentally and thermally stable materials that can be used as electrical conductors, nonlinear optical devices, polymer LEDs, photoresists, antistatic coatings, sensors, solar cells, microwave absorbing materials, polymer electronic interconnects, nanoelectronic and optical devices, and transistors.An assembly of ITO/nano-crystalline TiO2/polyaniline/ITO has been made in a simple way by our group. The junction thus obtained shows rectifying behaviour. Under the simulated sunlight which power is 50mW/cm2, the short-circuit current achieved 0.12mA and open circuit voltage achieved 0.38V. We synthesized poly(3-hexylthiphene), the absorption spectrum of which had a strong absorption peak in 500nm-600nm.In the paper a new inorganic- organic heterojunction solar cells is made using titanium dioxide (TiO2) and P3HT. Using Keithley, SMU2601, we obtained the open circuit voltage of 0.75V, short-circuit current of 0.8mA and the photoelectric conversion efficiency achieved 0.24 percent in AM1.5G light. It was found that the performance of the device with different solvents dissolved P3HT is wary widely, and the device performance is optimal when chlorobenzene as the solvent. The PEG was mixed into the TiO2 Sol in order to change the surface roughness of the TiO2 solid film. High film roughness can increase the contact area of the TiO2 and P3HT and improve device performance. By changing the concentration of the PEG, we found that it is best when mixed 1.5g PEG into 10g TiO2.Copper phthalocyanine(CuPc) is insert between TiO2 and P3HT as the photosensitive layer. The absorption spectra of CuPc have two peaks in 400nm-500nm and 600nm-700nm. After introduced CuPc between TiO2 and P3HT, the composite absorption spectra have been expansion markedly and have a strong absorption in 400nm-700nm. The photocurrent of the device reached 1.5mA and photoelectric conversion efficiency achieved 0.3%, which increased by 25% than that without CuPc. By comparing, we found that it is best when the thickness of the CuPc is 20nm.Through this paper, a detailed analysis about the various factors of the inorganic-organic heterojunction solar cell performance was carried out, and the device performance has been improved markedly through the introduction of the small organic molecules material (copper phthalocyanine) as a sensitive materials. Such inorganic-organic heterojunction that insert sensitization materials into the two-double device to improve device performance can be used in other organic polymer solar cells research as a device model.