Search

Nickel oxide (NiOX) is an ideal inorganic hole transport material for the fabrication of inverted perovskite solar cells owing to its excellent optical and semiconductor properties. Currently, the main research on developing the performance of NiOX‐based perovskite solar cells focuses on improving the conductivity of NiOX thin films and preventing the redox reactions between metal cations (Ni3+ on the surface of NiOX) and organic cations (FA+ or MA+ in the perovskite precursors) at the NiOX/perovskite interface. In this study, a new type of interface defects in NiOX‐based CsPbI2Br solar cells is reported. That is the Pb2+ from CsPbI2Br perovskites can diffuse into the lattice of NiOX surface as the annealing temperature of perovskites changes. The diffusion of Pb2+ increases the ratio of Ni3+/Ni2+ on the surface of NiOX, leading to an increase in the density of trap state at the interface between NiOX and perovskites, which eventually results in a serious decline in the photovoltaic performance of solar cells. [ABSTRACT FROM AUTHOR]

In conventional p–i–n inverted perovskite solar cells (PSCs), there exists considerable energy loss due to both unsatisfactory light path design and trap‐induced interfacial defects. The sunlight is absorbed competitively by conductive oxide substrates and hole transport material in front of the perovskite layer, while the opaque metal back electrode also prevents light penetration. Worse yet, there is severe nonradiative charge recombination caused by defects between the perovskite layer and the electron transport material. To tackle the above two issues, a new green‐emitting material ((CH3)4 N)2(C2H5)4N·MnBr4 is synthesized and introduced in/on the perovskite layer to achieve both defect passivation and light complementation. The green luminescence of this single crystal at the interface is found to provide secondary light absorption, as evidenced by a remarkable promotion of short‐circuit current density. It is also found that the excess PbI2 on the surface of perovskite can be effectively removed, and as the interfacial additive, ((CH3)4 N)2(C2H5)4 N·MnBr4 inhibits trap‐assisted recombination losses, which provides favorable energy‐level alignment and extends charge carrier lifetime. As a result, the champion PCE (21.23%) of the target‐treated ((CH3)4 N)2(C2H5)4 N·MnBr4 device exceeds that 19.5% of the pristine‐without ((CH3)4 N)2(C2H5)4 N·MnBr4 device. This work provides an effective interfacial strategy for high‐performance and stable inverted PSCs. [ABSTRACT FROM AUTHOR]

Two pervasive challenges encountered in inverted perovskite solar cells (PSCs) are difficulties in depositing high-quality and reproducible perovskite thin films and unsatisfactory device stability in ambient air. One constraint is the poor surface wettability of buried hole transport materials (HTMs) such as poly(triarylamine) (PTAA), which induces weak layer contact and impedes interfacial charge extraction. Another is that the impurity-induced surface defects of perovskite layers pose a significant threat to the stability and reproducibility of PSCs. To tackle these issues, we propose a strategy that introduces the amine molecule 4,4′,4′′-tris(3-methyl phenyl phenylamino)triphenylamine (m-MTDATA) into a PTAA/perovskite interface as a target modification to enhance the wettability of PTAA. The PTAA/m-MTDATA bilayer is found to align the energy levels of HTMs. Furthermore, phenyl ammonium bromide (PhABr) is deposited onto the perovskite surface to remove excessive residual PbI2 for the reduction of uncoordinated Pb2+ and iodide vacancies. A target device with m-MTDATA and PhABr achieves an impressive efficiency of 22.56% with negligible hysteresis, which is significantly higher than that of a pristine device (19.69%). Moreover, the device also shows significantly enhanced resistance to moisture, thermal stability and continuous light illumination. The strategy of target anchoring agents is feasible for high-performance inverted PSCs with enhanced stability. [ABSTRACT FROM AUTHOR]

The high stability and low toxicity of bismuth-based perovskite materials can overcome current issues of lead-based perovskite solar cells (PSCs). In this study, a stable 2-amino-4-picoline (2-4py)-based bismuth perovskite material [(C6H9N2)BiI4] was developed, which has a low band gap and high stability. A one-step solution spin-coating method was used to prepare (C6H9N2)BiI4 film as the light-absorbing layer. The electron transport layers were composed of compact TiO2 (c-TiO2) and mesoporous TiO2 (mes-TiO2). Measurements by UV–vis and time-resolved photoluminescence showed that the band gap of (C6H9N2)BiI4 film was 2.0 eV and the fluorescence lifetime was 21.58 ns. The materials were assembled into a device, and comparative experimental results showed that the highest power conversion efficiency of fluorine-doped SnO2 (FTO)/c-TiO2 + mes-TiO2/(C6H9N2)BiI4/Spiro-OMeTAD/Au was 0.0328%. Although the efficiency of the current device was low, the (C6H9N2)BiI4 material exhibited excellent stability in hot and wet conditions. This indicates that (C6H9N2)BiI4 has potential for use in highly stable solar cells. [ABSTRACT FROM AUTHOR]