Electron Acceptor Molecule Doping Induced π–π Interaction to Promote Charge Transport Kinetics for Efficient and Stable 2D/3D Perovskite Solar Cells

Abstract

Although the incorporation of 2D perovskite into 3D perovskite can greatly enhance intrinsic stability, power conversion efficiency (PCE) of 2D/3D perovskite is still inferior to its 3D counterpart due to poor carrier transport kinetics resulted from the quantum and dielectric confinement of 2D component. To overcome this issue, the electron acceptor molecule 1,2,4,5‐tetracyanobenzene (TCNB) was introduced to trigger intermolecular π–π interaction in 2D perovskite along with the electronic doping of 2D/3D perovskite to improve charge transfer efficiency. By virtue of high electron affinity, TCNB can undergo electron transfer reaction and subsequently establish π–π interaction with 1‐naphthalenemethylammonium (NMA) cations, greatly strengthening lattice rigidity and reducing exciton binding energy. Transmission electron microscopy results demonstrate that 2D phases are mainly distributed at grain boundaries, reducing defect density and weakening nonradiative recombination. Meanwhile, the p‐type doping of perovskite by TCNB optimizes energy level alignment at perovskite/hole transport layer interface. Consequently, PCE of champion device is significantly boosted to 24.01 %. The unencapsulated device retains an initial efficiency close to 94 % after exposure to ambient environment for over 1000 h. This work paves a novel path for designing new mixed‐dimensional perovskite solar cells with high PCE and superior stability.

Effect of A-Site Cations on Carrier Relaxation Dynamics of APbBr3 (A = Cs/MA/FA) Perovskite Nanoplatelets

“…15,16 Thus, carrier extraction is crucial for developing efficient photovoltaic applications in 2D NPLs. 31,32 It is reported theoretically and experimentally that the density of states for electrons and the number of phonon modes decreased with the reduction of dimensionality from 3D to 2D. 15,17 Thus, slower cooling times are expected for 2D LHPs due to the reduction of carrier−phonon scattering.…”

“…The low-dimensional confined LHP’s carrier cooling process exhibits a mechanism different from that of bulk LHPs. Generally, 2D CsPbBr 3 NPLs experience higher exciton binding energy nearly 350 meV due to strong confinement and reduced dielectric screening. , Thus, carrier extraction is crucial for developing efficient photovoltaic applications in 2D NPLs. , It is reported theoretically and experimentally that the density of states for electrons and the number of phonon modes decreased with the reduction of dimensionality from 3D to 2D. , Thus, slower cooling times are expected for 2D LHPs due to the reduction of carrier–phonon scattering . Practically, 2D LHPs NPLs exhibit a faster cooling rate due to the reduction of the screening of Coulombic carrier–LO–phonon interaction in the low-dielectric surrounding and quantum confinement effect .…”