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Introducing Optically Polarizable Molecules into Perovskite Solar Cells with Simultaneously Enhanced Spin-Orbital Coupling, Suppressed Non-Radiative Recombination and Improved Transport Balance towards Enhancing Photovoltaic Actions

Abstract

By considering facile molecular diffusion and optically generated electrical polarization, this article reports, for the first time, that directly introducing optically polarizable non-fullerene electron acceptor ITIC molecules into organic-inorganic hybrid perovskite (MAPbI3-xClx) films with uniform and non-uniform gradient distributions can surprisingly enhance the spin-orbital coupling (SOC) with the consequence of increasing the conversion from photogenerated spin-singlets to spin-triplets, boosting the spin states available for photovoltaic actions and enhancing the power conversion efficiency (PCE) from 15.3 % to 17.2 % with the Jsc of 20.2 mA/cm2, Voc of 1.08 V, and FF of 79 % in perovskite solar cells [ITO/PEDOT:PSS/MAPbI3-xClx/PCBM/PEI/Ag]. Specifically, we find that dispersing ITIC molecules can largely decrease the Jsc (photocurrent difference) generated by switching the photoexcitation from linear to circular polarization with same intensity. This phenomenon provides a direct evidence that the dispersed optically polarizable ITIC molecules can increase the SOC in organic-inorganic hybrid perovskites through the interaction between introduced electrical polarization and SOC. Furthermore, impedance studies indicate that dispersing ITIC molecules can decrease the density of trap states by passivating the grain boundary defects and simultaneously increases the carrier mobilities. Consequently, the non-radiative recombination is reduced upon decreasing the density of trap states through dispersing the ITIC molecules, according to transient photoluminescence studies. The UV-Vis and FTIR spectral studies indicate a bounding formation between the Pb and N and O, showing a direct interaction between the hybrid perovskite MAPbI3-xClx and dispersed ITIC molecules. Clearly, introducing optically polarizable non-fullerene electron acceptor molecules presents a new opportunity to enhance photovoltaic actions in perovskite solar cells through SOC and grain boundary passivation effects.

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Publication details

The article was received on 01 Mar 2018, accepted on 13 Apr 2018 and first published on 13 Apr 2018


Article type: Paper
DOI: 10.1039/C8TC01033A
Citation: J. Mater. Chem. C, 2018, Accepted Manuscript
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    Introducing Optically Polarizable Molecules into Perovskite Solar Cells with Simultaneously Enhanced Spin-Orbital Coupling, Suppressed Non-Radiative Recombination and Improved Transport Balance towards Enhancing Photovoltaic Actions

    C. Han, H. Yu, J. Duan, K. Lu, J. Zhang, M. Shao and B. Hu, J. Mater. Chem. C, 2018, Accepted Manuscript , DOI: 10.1039/C8TC01033A

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