Synergistic effects of the physical modification and chemical passivation enabling efficient perovskite solar cells

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Inverted perovskite solar cells (IPSCs) with poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as hole transport materials exhibit superior stability and low-temperature processibility. However, the hydrophobicity of PTAA renders it difficult to prepare high-quality perovskite films due to the low wettability of perovskite precursor solutions, resulting in poor crystallization of perovskites and undesirable interface properties of PTAA/perovskites. Herein, a porous layer of Al2O3 nanoparticles functionalized using 2-thenoylacetonitrile (2-T-OACN) molecules is incorporated into the PTAA/perovskite interface. The physical adhesion of Al2O3 nanoparticles on the PTAA layer could enhance the surface wettability for perovskite precursor solutions, resulting in uniform perovskite films being realized on the PTAA layer. Meanwhile, 2-T-OACN adsorbed on the Al2O3 nanoparticles could form C=O··· Pb2+ and C≡N ···Pb2+ coordination interactions with the bottom surface of perovskites, thus passivating the defects at the PTAA/perovskite interface. Moreover, the electron-rich thiophene groups in 2-T-OACN molecules further promote interfacial charge carrier transport and thus significantly lower the interfacial recombination. Consequently, the IPSCs show a high efficiency of 23.3 %, which is largely improved compared with that of 19.4 % efficiency for control IPSCs. The synergistic strategy of the physical modification and chemical passivation provides a feasible approach for modulating the crystallization of perovskites and buried interface properties for IPSCs.