| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 103 === Solar cells based on methyl ammonium lead iodide perovskite as light absorbers have gained much attention owing to its high efficiency and low fabrication cost. Two device structures namely mesoscopic nanocomposite and planar heterojunction have achieved high efficiencies. These superior conversion efficiencies were achieved through extensive manipulation of the device components like perovskite composition, TiO2 layers and/or interface engineering. These complicated methods are essential to get the best efficiency but quite challenging to reproduce. A one-step solvent assisted crystallization technique is introduced in the mesostructured perovskite solar cells for the first time. Solvent assisted crystallization technique is performed by drop-casting of chlorobenzene on spinning substrate with CH3NH3PbI3 perovskite precursor solution dissolved in DMF. Analysis of the film morphology using scanning electron microscopy revealed that the perovskite layer deposited by solvent assisted crystallization technique consists of an extremely uniform and dense perovskite crystalline grains. Mesoscopic nanocomposite perovskite solar cells fabricated by solvent assisted crystallization technique demonstrate the highest power conversion efficiency of 16.92% and an average power conversion efficiency of 15.41% (s.d. ± 0.75) calculated for 60 devices under standard AM 1.5G illumination. As a comparison, planar heterojunction perovskite solar cells were fabricated using the same condition resulting in best performing device with the power conversion efficiency of 13.33% (s.d. ± 1.19) and an average power conversion efficiency of 10.43% over 12 devices. The hysteresis effect is also reduced by a large extend due to the mesoscopic architecture compared to the planar heterojunction devices. As far as our knowledge, the work from this thesis has led to achieve the second best efficiency reported for a mesoscopic nanocomposite perovskite solar cell based on spiro-OMeTAD as a hole transporting material without any extensive manipulations on the chemical compositions and exhausted device optimization by using all commercially available ingredients. These results provide an important insight towards the understanding of the significance of solution processed device in the realization of highly efficient, highly consistent, and low-cost perovskite solar cells.
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