Electronic interaction and emission characteristics of perovskite/organic hybrid films

Understanding the interaction between perovskites and organic molecules is crucial for optimizing hybrid materials in advanced optoelectronic applications, such as light-emitting diodes (LEDs) and photovoltaic devices. In this study, density functional theory calculations and experimental analyses were employed to investigate the interfacial interactions between perovskites and a series of organic molecules, including 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP), bis(2-methyldibenzo[f,h]quinoxaline)(acetylacetonate) iridium(III) (Ir(MDQ)2acac), bis(1-phenylisoquinoline)(acetylacetonate)iridium(III) (Ir(piq)2acac), 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB), and 2-[4-(diphenylamino)phenyl]-10,10-dioxide-9H-thioxanthen-9-one (TXO-TPA). Although considerable binding energies exist between the perovskite and all the organic molecules, the experimental results reveal that not all passivated devices exhibit improved performance. This suggests that other factors, beyond binding energy, play a significant role in determining device performance. Theoretical calculations reveal charge transfer from the perovskite to all the organic molecules exists at the ground state of the perovskite, while experimental tests reveal that charge transfer from the perovskite to organic molecules only occurs in the condition of favored energy level alignment. The exciton lifetime and the photoluminescence intensity of the perovskite are reduced by the organic molecules except CBP, deriving from the charge transfer induced exciton quenching of the perovskite. Moreover, no evident energy transfer from perovskite to organic molecules is observed, despite the obvious spectra overlap between the perovskite emission and the absorption of the organic molecule. This study provides critical insights into the diverse interaction mechanisms between perovskite and organic molecules, highlighting the pivotal role of charge transfer in determining carrier dynamics and luminescence behaviors, while also emphasizing the complexity of factors influencing device performance.