Study On The Preparation Of Flexible Perovskite Solar Cells At Low Temperature Processing

Flexible solar cells have caught scientists’eyes due to their great potentials in applications of different fields,such as civil engineering,consumer electronics,electric vehicles and aerospace applications.Perovskite solar cells（PSCs）have made a remarkable progress in recent years,with their power conversion efficiencies（PCEs）soaring from 3.8%to 25.5%in the past decade.Due to the intrinsic flexibility and their low-cost and facile manufacturing process,perovskites are undoubtedly considered as a promising candidate for the next generation of flexible solar cells.Up to now,the PCE of single-junction flexible PSCs has reached 21%,which keeps the researchers enthusiastic about the further development and applications of flexible PSCs.At present,flexible PSCs are mainly based on the commonly-used organic polymer polyethylene terephthalate（PET）and polyethylene naphthalate（PEN）as the flexible substrates.Temperature higher than 150℃will cause irreversible damages to the polymer substrates.Thus each functional layer of the flexible devices must be fabricated at low temperature.However,conventional high-efficiency PSCs commonly involve high-temperature fabrications of the perovskite absorption layer and the electron transport layer（ETL）.There remains challenging for further improvement in flexible PSCs.Thus,in this work,we mainly focus on fabricating flexible PSCs in low temperature process.We succeeded in manufacturing perovskite layer and ETL at low temparature processing,and obtained high efficiency flexible PSCs device.Based on the fact that CH₃NH₃Pb X₃ can formαphase at room temperature,by simply adding CH₃NH₃Br（CH₃NH₃⁺,MA）in the dynamic rotation of the perovskite precursor,theα-phase crystal seeds were formed.The formation energy ofα-phase Formamidine（FA）-based perovskite could be significantly reduced to 40℃through a similar epitaxial growth method at heating process.We successfully address the problem that traditional PSCs light absorption layer anneal at 150℃or use poisonous solvent for a low temperature processing.By studying the crystal structure,surface morphology and optical performance of the perovskite film prepared at different annealing temperature,a high quality FA perovskite film with excellent photoelectric performances has achived at an optimized temperature of 100℃.By using tin dioxide aqueous solution colloids as precursors,the spin-coating method successfully manufactures tin dioxide film below the tolerence temperature of the flexible substrate,which is vital for the preparation of flexible PSCs.By adjusting the growth and crystallization quality of Sn O₂ crystals,the prepared ETL can not only transmit sunlight effectively,but also have excellent Electron transport performance.After optimization,the PCE of the optimal flexible PSCs reached 18.5%and retained more than 80%of its initial PCE after 1200 bending cycles.This is by far the best performance for the preparation of flexible PSCs at low temperature（100°C）without antisolvent.