| Perovskite solar cells（PSCs）become a potential candidate for new generation of photovoltaic technology due to the excellent efficiency,solution processability,and low cost.Polycrystalline perovskite films exhibit outstanding flexibility and can be fabricated using a roll-to-roll printing method,which is ideal for large-scale manufacturing.As a result,flexible perovskite solar cells（FPSCs）are regarded one of the most significant developing directions for PSCs.However,enormous obstacles remain to hinder the process of industrialization for FPSCs.Several issues,such as crystal quality of perovskite on flexible substrate,interfacial and bulk defects and the limit of fabrication technology,also impede the advancement of performance of FPSCs.The power conversion efficiency（PCE）and operational stability of FPSCs still lag considerably behind that of rigid PSCs.Meanwhile,mechanical stability of FPSCs is still a hindrance for their practical applications.In comparison to regular structure（n-i-p）,inverted FPSCs have a significant advantage for its low-temperature processibility and mechanical stability.As a result,this thesis will concentrate on inverted FPSCs.Considering the limitations of performance and stability of FPSCs,we proposed innovative solutions based on additive engineering and interfacial engineering,focusing on the optimization of perovskite crystal quality and the structure of device in FPSCs to achieve the improvement of PCE and stability of inverted FPSCs simultaneously.The main achievements are as follows:1.Enhanced PCE and stability of FPSCs by using HPbI3 additive.The efficiency and mechanical stability of methylamine-free（MA）based FPSCs were increased synchronously by introducing an optimum quantity of HPbI3 additive into the perovskite precursor solution.The HPbI3 additive facilitated the improvement of the surface morphology and crystallinity of the perovskite films,as well as the improvement of the work function.The energy level of perovskite was more in tune with the charge transport layer,resulting in enhanced device performance.As a result,PCEs of 20.1%and 18.74%were obtained for the rigid and flexible PSCs,respectively.The resulted FPSCs maintained 90%and 70%of the initial PCE value after 1200 and5000 bending cycles,respectively,under a bending radius of 4 mm.2.Enhancing PCE and stability of FPSCs by in-situ oligomer crosslinking in the grain boundaries.The major challenges in the practical applications of FPSCs are efficiency,operational stability,and mechanical stability.Herein,we developed a facile approach by incorporating a cross-linkable oligomer of trimethylolpropane ethoxylate triacrylate（TET）into perovskite films to simultaneously enhance the PCE and stability of FPSCs.A PCE of 20.32%was achieved for inverted FPSCs.Meanwhile,both mechanical and environmental stabilities were improved for the TET-incorporated FPSCs due to filling of grain boundaries with hydrophobic crosslinking polymer.In particular,the PCE retained approximately 87%of its initial value after 20000 bending cycles at a radius of 4 mm.The inverted FPSCs retained 85%of the initial PCE after500 h storage at 85°C and 90%after 900 h continuous one-sun illumination.A joint experiment–theory analysis ascribed the underlying mechanism to the reduced defect densities,improved crystallinity,and stability of the perovskite absorbers on flexible substrates caused by TET incorporation.3.Enhancing PCE and stability of FPSCs by using the imprint-assisted growth of2D/3D perovskite method.Eliminating interfacial and bulk defects of perovskite films has always been stressed for the preparation of perovskite films.Traditional solution passivation process employing spin-coating method is not very suitable owing to its issue of uniformity.More effective and uniform passivation technics especially for FPSCs need to be developed.Herein,we developed an efficacious and precise imprint-assisted growth of 2D/3D perovskite method to simultaneously fabricate a 2D/3D heterostructure perovskite absorber and reducing both interfacial and bulk defects.In the processing procedure,high-quality 2D/3D perovskite absorber with preferred orientational grain growth was obtained,which effectively suppress the ion migration and water/oxygen permeation.The resulted inverted FPSCs achieved a record PCE of21.01%,and it was noteworthy that the PCE retained about 80%of its initial value even after 10000 bending cycles under a bending radius of 3 mm.Additionally,the resulted inverted PSCs exhibited an excellent operational and environmental stability and achieved a remarkable certified efficiency of 22.93%. |
