A Generalized Method For Printing High-quality Perovskite Thin Films By Vacuum-quenching Assisted Crystallization

Metal halide perovskite solar cells?PSCs?have great potential in photovoltaic applications due to their superior photoelectric properties such as high absorption coefficient,long carrier diffusion lengths and high trap tolerance.At present,the photoelectric conversion efficiency?PCE?of small-sized solar cells prepared by spin-coating in laboratory has reached 25.2%,which already meet the requirements for industrial production.However,the biggest bottleneck of spin-coating is that it is neither scalable nor can be translated to other scalable deposition processes,which seriously hinders the commercial application of PSCs.In addition,the perovskite films fabricated by solution-processing inevitably introduce a large number of defects.Reducing the non-radiative recombination centers through defect passivation is an effective way to improve the photoelectric properties.In this thesis,we first introduce our attempt to develop a generalized crystallization protocol for the deposition of large-area perovskite films by scalable blade coating.The second part is focused on the photovoltaic performance improvement via defects passivation.1.We firstly developed a scalable printing process for preparing perovskite films based on vacuum-quenching assisted crystallization.The deployment of the vacuum is able to effectively decouple the two most important crystallization processes,nucleation and crystal growth,which often overlap each other during film deposition.Based on the vacuum-quenching method,large-area perovskite films with uniform and dense crystalline grains were prepared by blade coaitng.Perovskite solar devices with an active layer area of 0.09 cm² and solar modules with an area of 10.08 cm² delivered PCE of 18.01%and 11.25%,respectively.2.In the second part,we employed a biopolymer,poly-L-lysine,which contains aboudant of amino?-NH₂?and carboxyl?-COOH?functional groups to passivate the defects of polycrystalline perovskite films.It is found that the Lewis base of-NH₂ can reduce lead-iodine antiside defects,while the-COOH can suppress the formation of lead element.Compared with the control devices,the V_OC of the passivated devices was increased by nearly 100 m V,and the PCE was increased to 19.45%.