Research On Preparation Of Efficient And Stable Perovskite Solar Cells Based On Interface Engineering

In recent years,due to the excellent photoelectric properties of perovskite materials and their facile preparation processes,the power conversion efficiency(PCE)of perovskite solar cells has achieved over 25%rapidly,becoming a research hotspot in the field of novel photovoltaics.Perovskite solar cells(PSCs)are expected to become the next generation of commercial solar cells.However,the efficiency and stability of PSCs are still being improved in order to meet critical requirements for the further commercialization.By increasing the open circuit voltage(V_OC)of the devices is the most effective method to improve the device efficiency.Surface defects of perovskites have been recognized as one of the most important issues in V_OC,which affect the separation and extraction of interfacial charge carriers,lead to a large number of non-radiative recombination and reduce the photovoltaic performance and stability of devices.To solve the above issues,we systematically investigate the effect of Cs Pb Br₃quantum dots and phenmethylammonium iodide(PMAI)on charge transport and efficiency of perovskite solar cells,respectively,from the perspective of carrier dynamics and electrical properties.The effect of interfacial dipoles on the built-in electric field is quantitatively analyzed.The results reveal the effect of field-effect passivation on quasi-Fermi level splitting(QFLS),demonstrating the intrinsic mechanism that dominates the observed significant increase in V_OC.The main research contents of this paper are as follows:By introducing Cs Pb Br₃ quantum dots between the perovskite and hole transport layer,we elucidate the effect of quantum dots on charge transport and carrier dynamics of perovskite solar cells.The results reveal that the separation and extraction of charge carriers are promoted by Cs Pb Br₃ quantum dots,leading to reduction in the charge transport resistance of the interface.Thus the PCE of devices are increased.Finally,the optimized PSCs show a champion PCE of 21.7%with a high fill factor of 82.2%.Phenmethylammonium iodide(PMAI)is applied as the interface passivation layer through the surface post-treatment strategy.It is found that the deposition of PMAI leads to formation of oriented dipoles which induces an enhancement of the built-in electric field.The enhanced filed is able to restrain the non-radiative recombination at the interface,leading to a significant field-effect passivation effect.Through simulation and quantitative analysis of the carrier dynamics,it is clarified that the field-effect passivation can effectively improve the hole quasi-Fermi level splitting thus dominate the significant increase in V_OC by 100 m V.Finally,the devices based on the PMAI surface post treatment obtain a champion PCE of 22.6%with a high V_OC of 1.17 V.Meanwhile,the long-term stability of the devices is significantly improved due to the hydrophobicity of the benzene ring in PMAI and the inhibition of interfacial ion migration by the interfacial treatment.Our study comprehensively reveals the effect of surface dipoles on the V_OC of perovskite solar cells and provides an effective way to enhance the V_OC through polar materials.