We report a low-cost, free-hole conductor methylammonium lead iodide CH 3 NH 3 PbI 3 (perovskite)/ZnO nanorods (NR) heterojunction solar cell. ZnO nanorod arrays were obtained electrochemically onto transparent conducting oxide (fluor doped tin oxide, FTO) from an aqueous solution of zinc acetate. The ZnO NR were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical transmittance. Solar cell was fabricated forming the perovskite material onto the ZnO thin film. Spin coating of an equimolar mixture of CH 3 NH 3 I and PbI 2 in γ-butyrolactone solution (perovskite precursor solution) leads to CH 3 NH 3 PbI 3 formation on ZnO NR. A graphite-covered FTO/glass was used as a back contact. The photovoltaic performance of the solar cell was characterized at full sun intensity of 100 mW/cm 2 obtaining a shortcircuit current of 1.5 mA/cm 2 , an open circuit voltage of 0.47 V and energy conversion efficiency of 0.16 %.Keywords: Solar cells, Organic-Inorganic Perovskites, Zinc Oxide, Nanorods.
INTRODUCTIONEnergy plays an important role in the economic future of countries. This problem is a global issue for our planet, aggravated by the fact that in the forthcoming decades, due to an increasing world population, energy demand will increase significantly. Conservative estimates implies that fossil fuels may be exhausted during the decade of 2040s 1 , with the serious consequences that this entails. It is expected that in future, solar energy will play a major role as an alternative energy source. The Sun provides Earth with as much energy every hour as human civilization uses every year 2 . Therefore, harvesting a small fraction of incident solar irradiation could meet our growing energy demand. Realizing the full potential of this vast energy source requires a new generation of photovoltaics that are both efficient and cost-effective.Nowadays, the cristallyne silicon solar cell corresponds to the most used photovoltaic technology. However, the manufacturing of this kind of solar cell demands a great amount of energy. Purifying and crystallizing the silicon are the most energy intensive parts of the solar cell manufacturing process. In this case the EPBT (Energy Payback Time, the length of time a PV system takes to generate the amount of energy put into system) is as long as 2.7 years.Organic-inorganic perovskite-based solar cells have recently emerged as a transformative photovoltaic (PV) technology. Perovskite solar cells based on titanium dioxide, a CH 3 NH 3 PbI 3 light-absorption layer and spiro-OMeTAD as hole transporting material have achieved power conversion efficiencies as high as 15.0 % 3 , making it competitive with thin-film PV technology. Several reports suggest that solar cells with efficiencies up to 20% are realistically achievable 4-5 . The most attractive aspects of this technology are the simplicity of photoactive layer synthesis and application using benchtop approaches at temperatures less than 100°C. 6 Besides, the perovskite material exhibit optimal characteri...