Device Modification And Interface Study Of Organic And Organic/Inorganic Hybrid Solar Cells

As a promising clean and renewable source, sunlight attracts great attention as alternative of fossil fuels. The energy from the sun reaches the earth is estimated to be a year, which is 10000 times more than the global energy consumption. Solar cell at an efficiency of 10% would cover the energy needs of the whole world with converting 0.1% of the earth’s sunlight.Silicon solar cells typically require sophisticated high temperature process, high quality silicon and complicated engineering, therefore, they are not effective as an energy source. Organic solar cells(OSCs) are a promising renewable energy source for their low cost, light weight, easy fabrication, and potential flexibility.The present work is embedded in the field of organic photovoltaic devices, mainly about the device modification and interface study of organic and organic/inorganic hybrid solar cells.1) Demonstrated an improved PCE by 35% in Cu Pc/C60 based OSCs by using the 2-D PS nanophere periodic structure as an efficient light trappings scheme. The light-trapping structure was fabricated via colloidal lithography or nanosphere lithography using polystyrene nanospheres. The photocurrent showed noticeable enhancement compared to the planar structure based cell at some wavelength range, which was agreed well with the FDTD simulations. The improvement in device performance was mainly attributed to the increased optical path length and the efficient light trapping. This process known as NSL is easily tunable and is a promising option to realize high-efficiency and low-cost OSCs.2) The origin of severe efficiency discrepancy of perovskite solar cells(PSCs) under ambient air condition was investigated. Two sets of PSCs were fabricated by thermally annealing the perovskite films either in a nitrogen-filled glove box or in the ambient air, respectively. The measurements of optical property, surface morphology and electronic structure reveal that the perovskite film morphology can be modulated during the annealing process, but the electronic structure of the controlled perovskite films was not altered substantially, and the severe efficiency discrepancy is mainly associated with the degraded absorption due to the poor morphology of the perovskite films in ambient air.3) The interfacial electronic structure of solution-processed perovskite/fullerene junctions is directly measured by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The results showed that both junction are found to be N-N junctions rather than the generally believed P-N junctions. Meanwhile, devices with perovskite/C60 and perovskite/PCBM junctions show reasonable performance. These results experimentally confirm that excitons are dissociated into free carriers in perovskite film.