Preparation And Photovoltaic Performance Of Polyamide-amine Dendrimer Modified Perovskite Solar Cells

Organic-inorganic hybrid perovskite materials have been widely used in the field of solar cells because of their advantages such as long carrier diffusion length,high light absorption coefficient,low carrier recombination rate,bandgap tunability.The power conversion efficiency（PCE）of perovskite solar cells has soared from 3.8%in2009 to 25.2%at present.For perovskite solar cells,the morphology and crystallinity of the perovskite film are the most important factors affecting the PCE value.In addition,the perovskite films are prone to degradation in air,resulting in poor environmental stability.Therefore,the improvement of perovskite morphology and environmental stability is the current focus of perovskite solar cells.Since the polymers could play an important role in improving the perovskite morphology and environmental stability,polyamide-amine dendrimer（PAMAM）is synthesized and introduced into the perovskite film in order to obtain stable and high efficient perovskite solar cells.（1）1.0G,2.0G,3.0G and 4.0G polyamide-amine dendrimer were synthesized through Michael addition and amidation reaction,and their amine-terminated groups were protonated.Their chemical structures were characterized by ¹H-NMR and FT-IR spectra.（2）The effects of different contents of protonated polyamide-amine dendrimers modification on perovskite solar cells were investigated.Perovskite solar cells with a structure of FTO/Ti O₂/Perovskite/Cu SCN/Ag were prepared by introducing different generations of protonated polyamide-amine dendrimers into perovskite precursor solution at the ratios of 0%,0.5%,1%,2%and 5%respectively.XRD,UV-vis and PL results show that the perovskite films containing 1%dendrimers have good crystallinity,high absorbance and few defects.The AFM diagrams of the perovskite films show that the RMS value of the unmodified film is 11.81 nm while that of the films modified by1%4.0G dendrimer is 7.37 nm.This indicates that the smoother and denser perovskite film can be obtained through the protonated PAMAM modification.According to the photovoltaic performance test,the PCE value of unmodified perovskite solar cells is7.21%while that of PAMAM-modified perovskite solar cells first increases and then decreases with the PAMAM content increase.The optimal PCE value of 13.11%is obtained when 4.0G PAMAM dendrimer is incorporated.（3）Keeping the doping content at 1%,perovskite solar cells with a structure of FTO/Ti O₂/Perovskite/spiro-OMe TAD/Ag were prepared to investigate the effect of PAMAM generation on the photovoltaic and stability performance.The XRD and UV-Vis results show that the perovskite film modified by high generation of dendrimer has better crystallinity and higher light absorption.The AFM diagrams show that the RMS value of the unmodified film is 9.90 nm while the RMS value of the 4.0G protonated PAMAM modified film is reduced to 4.78 nm,indicating that dendrimers modification with higher generation can obtain films with smoother surface and less roughness.The device charge transfer resistance is reduced from 27.83 KΩin the unmodified device to 8.07 KΩin the 4.0G protonated PAMAM modified device,revealing the improvement of carrier transfer efficiency.According to the photovoltaic performance test of the device,the PCE value of the unmodified perovskite solar cells is 10.82%while the PCE of the polymer modified perovskite solar cells improve with the increase of the incorporation generations.The optimal PCE of 16.03%is obtained with an increase of 48%when 4.0G dendrimers are incorporated.After being left for 20 days under ambient conditions,the PCE of 4.0G dendrimer-modified perovskite solar cells can be maintained above 75%of the original PCE while the efficiency of the unmodified perovskite solar cells decay below 10%of the original PCE,showing the improvement of environmental stability of the device.