The Application Of Inorganic Halide Perovskite In Perovskite Solar Cells

Perovskite solar cells?PSCs?have attracted extensive attention since 2009.The power conversion efficiency?PCE?increased rapidly from 3.8%to 23.7%,close to that of monocrystalline silicon solar cells.Although high PCE has been achieved,organic-inorganic hybrid perovskites commonly suffer poor stability in the ambient environment?such as moisture,oxygen,heat and ultraviolet?,due to the decomposition of labile organic cations?such as methylamine and formamidine?.The ideal solution to improve its stability is to completely replace the organic cations with inorganic cations?such as Cs⁺and Rb⁺?.Up to now,some progress has been made in the inorganic perovskite solar cells?I-PSCs?.However,there are still many shortcomings in the I-PSCs and the PCEs are significantly lower than those of organic-inorganic hybrid perovskite solar cells?OIH-PSCs?.Therefore,this thesis focuses on the application of inorganic perovskite CsPbX₃?X=Cl,Br,I?in PSCs,aiming to prepare high-efficiency and high-stability I-PSCs.Firstly,the structure and properties of CsPbX₃ nanocrystals?NCs?are studied,and the incorporation of CsPbBr₃ NCs in organic-inorganic hybrid perovskite are explored.Then,high-efficiency CsPbI₂Br PSCs are prepared through process optimization.Finally,two-dimensional components are introduced into CsPbI₂Br to improve its environmental stability.Specific research contents include:?1?CsPbX₃ NCs are synthesized in two different ways?hot-injection approach and room-temperature ligand-assisted reprecipitation method?,and their structures and properties are characterized.The bandgap energies are readily tunable through composition and size modulations.Furthermore,the shape of colloidal CsPbX₃ NCs are systematically manipulated.?2?The CsPbBr₃ NCs dispersed in chlorobenzene are used as a dripping solvent to further construct the graded heterojunction of FAMA-based perovskite by one-step deposition process.The coherence in structure and stoichiometry and compatibility in processing upon the incorporation of NCs,significantly improves the as-resulted heterojunction without hampering its optoelectronic properties.Appropriate band alignment is achieved to facilitate the hole extraction and to reduce recombination loss.By employing this strategy,a best PCE of 20.56%is achieved in the resultant device.In addition,the incorporation of CsPbBr₃ NCs also improves the thermal stability of the PSCs.?3?A simple low temperature solution process is developed to deposit inorganic CsPbI₂Br perovskite films with high quality.Via optimized solvent engineering and enhanced mass transport,uniform and pin-hole free?-CsPbI2Br films are obtained to achieve a stabilized PCE of 14.31%based on the planar heterojunction solar cell.Importantly,the devices show excellent long-term stability,which maintain 91.58%of their original efficiency after 120 days stored in dark under room temperature.Furthermore,the based devices also exhibit a remarkable long-term thermal stability with only 16.42%PCE decline after being heated at 85? for 500 h and the devices can maintain 90.33%of their original efficiency after 500 h of continuous light soaking.?5?In view of the problem that inorganic CsPbI₂Br is sensitive to moisture,phenylethylammonium iodide?PEAI?is introduced into the system to reduce the dimension of CsPbI₂Br,thereby stabilizing the?-CsPbI₂Br phase.Highly efficient and stable quasi-2D CsPbI₂Br PSCs are obtained by modulating the amount of PEAI in the perovskite precursor solution.The corresponding PSCs achieve a best PCE of 14.80%,and still maintain 80.14%of the original efficiency after 30 days stored in the ambient environment.Furthermore,the devices can maintain 80.00%of their original efficiency after being heated at 85? for 500h.