Phase Control And Modification Of The Light-absorbing Layer Of Quasi-two-dimensional Perovskite Solar Cell

In recent years,organic-inorganic hybrid perovskites are focus of intensive attention due to their excellent photoelectric properties,such as long carrier diffusion length,high absorption coefficient,high carrier mobility,low density of deep electronic trap states and solution processing.At present,the highest efficiency of three-dimensional(3D)perovskite solar cells exceeds 25%,but the instability of 3D perovskite solar cells is caused by moisture,heat and light,which has greatly limited further development and practical application of 3D perovskite solar cells.Recently,two-dimensional(2D)perovskites have attracted the interest of researchers owing to its superior environmental stability and tunable bandgap.However,compared to the 3D perovskites,the efficiency of 2D perovskite solar cells is still low.In this article,(BA)2(FA)8Pb9I28 quasi-2D perovskite films are prepare with hydrochloric acid(HCl)additive by one-step solution spin coating method.We found that HCl additive can effectively regulate the distribution of the 2D/3D perovskite phases,and suppressing the non-radiative recombination of the perovskite film.Thereby improving the efficiency and stability of the device.On this basis,the introduction of the organic small molecule material PCBM in the antisolvent can improve the quality of the perovskite film and its carrier transport performance.The efficiency of the solar cells is further improved.Finally,a highly efficient and stable(BA)2(FA)8Pb9I28 quasi-2D perovskite solar cell is obtained.The corresponding works are shown as follows:1.Perovskite films are prepared with HCl additive by one-step spin coating method.By conducting steady-state PL tests on the front and back of the(BA)2(FA)8Pb9I28 quasi-2D perovskite films,we found that HCl additives can effectively suppress the vertical phase separation in the quasi-2D perovskite.The nearly homogeneous distribution of perovskite film shows a strong PL intensity and fluorescence lifetime,indicating that the non-radiative recombination inside the perovskite film is effectively suppressed.By characterizing the unannealed films,we found that HCl can inhibit the prior formation of 2D perovskite phases during the formation of perovskite films,hence suppress the segregation of 2D/3D perovskite phases.With 30 ul/ml HCl additive in the precursor,the power conversion efficiency(PCE)of the device reaches 13.16%,the short-circuit current density is 18.89 mA/cm2,the open circuit voltage is 1.102 V,and the fill factor is 63.22%.The film did not show any decomposition after stored in ambient air with 35%±5%relative humidity,exhibiting the excellent humidity stability.2.On the basis of the first subject,we modified the(BA)2(FA)8Pb9I28 quasi-2D perovskite films by introducing an organic small molecule material PCBM additive into the anti-solvent.According to the XRD and KPFM images,we found that PCBM can improve the crystal quality and reduce the root-mean-square roughness of the perovskite films.At the same time,the results of PL and TRPL show that PCBM can not only passivate the defects and traps of the perovskite film,suppress the non-radiative recombination,but also improve the electron transport performance and the carrier transport efficiency of the perovskite films.The quasi-2D perovskite solar cells prepared based on this method exhibit excellent PCE.By optimizing the addition of PCBM,the PCE of perovskite solar cells increase from 13.46%to 15.01%,and the hysteresis of the device is also significantly suppressed.