Passivation of electronic defects on the surface and at grain boundaries (GBs) of perovskite films has become one of the most effective tactics to suppress charge recombination in perovskite solar cells. It is demonstrated that trap states can be effectively passivated by Lewis acid or base functional groups. In this work, nicotinamide (NTM, commonly known as vitamin B3 or vitamin PP) serving as a Lewis base additive is introduced into the PbI2 and/or FAI: MABr: MACl precursor solution to obtain NTM modified perovskite films. It has been found that the NTM in the perovskite film can well passivate surface and GBs defects, control the film morphology and enhance the crystallinity via its interaction with a lone pair of electrons in nitrogen. In the presence of the NTM additive, we obtained enlarged perovskite crystal grain about 3.6 μm and a champion planar perovskite solar cell with efficiency of 21.72% and negligible hysteresis. Our findings provide an effective route for crystal growth and defect passivation to bring further increases on both efficiency and stability of perovskite solar cells.

Nicotinamide as Additive for Microcrystalline and Defect Passivated Perovskite Solar Cells with 21.7% Efficiency.

In recent years, 2D Ruddlesden-Popper (2DRP) perovskite materials have been explored as emerging semiconductor materials in solar cells owing to their excellent stability and structural diversity. Although 2DRP perovskites have achieved photovoltaic efficiencies exceeding 19%, their widespread use is hindered by their inferior charge-carrier transport properties in the presence of diverse organic spacer cations, compared to that of traditional 3D perovskites. Hence, a systematic understanding of the carrier transport mechanism in 2D perovskites is critical for the development of high-performance 2D perovskite solar cells (PSCs). Here, the recent advances in the carrier behavior of 2DRP PSCs are summarized, and guidelines for successfully enhancing carrier transport are provided. First, the composition and crystal structure of 2DRP perovskite materials that affect carrier transport are discussed. Then, the features of 2DRP perovskite films (phase separation, grain orientation, crystallinity kinetics, etc.), which are closely related to carrier transport, are evaluated. Next, the principal direction of carrier transport guiding the selection of the transport layer is revealed. Finally, an outlook is proposed and strategies for enhancing carrier transport in high-performance PSCs are rationalized. 

Charge‐Carrier Transport in Quasi‐2D Ruddlesden–Popper Perovskite Solar Cells

Effective lewis base additive with S-donor for efficient and stable CsPbI2Br based perovskite solar cells

Excess PbI2 evolution for triple-cation based perovskite solar cells with 21.9% efficiency

Morphology control of SnO2 layer by solvent engineering for efficient perovskite solar cells

Cesium (Cs) contained triple-cation and mixed halide perovskite (CsFAMA) is broadly employed as light absorption layers for efficient and stable perovskite solar cells (PSCs) fabrication with high ...

Effects of Annealing Time on Triple Cation Perovskite Films and Their Solar Cells.

The synergistic effect of co-solvent engineering and thermal engineering towards phase control two-dimensional perovskite solar cells

As a famous hole transporting material, nickle oxide (NiOx) has drawn enormous attention due to its low cost and superior stability. However, the relatively low conductivity and high-density surface trap states of NiOx severely limit device performance in solar cell applications. Interfacial engineering is an efficient approach to achieve remarkable hole-transporting performance by surface passivation. Herein, the efficient NiOx hole transport layer was prepared by surface passivation engineering strategy via facile solution processes with cesium iodide (CsI). It is demonstrated that CsI plays a super-effective dual-function role in inverted solar cell device: On one hand, the presence of CsI hugely passivates the surface trap states at the NiOx/perovskite interface along with obviously improved conductivity by the incorporated Cs+; on the other hand, the ions immigration is significantly suppressed by the presence of I ion for high-quality perovskite films, resulting in a stable contact interface. The ameliorative interface leads to largely reduced carrier non-radiative recombination, attributing to boosted carrier extraction efficiency. As a result, decent power conversion efficiency (PCE) of 18.48% with a noticeable fill factor (FF) beyond 80% was achieved. This facile and efficient surface engineering approach with dual-function shows excellent potential for the design of high-performance functional interfacial modification layer to achieve high-performance solar cells.

Efficient carrier transport via dual-function interfacial engineering using cesium iodide for high-performance perovskite solar cells based on NiOx hole transporting materials

Taotao Hu

Papers

Effects of Annealing Time on Triple Cation Perovskite Films and Their Solar Cells.

The synergistic effect of co-solvent engineering and thermal engineering towards phase control two-dimensional perovskite solar cells

Efficient carrier transport via dual-function interfacial engineering using cesium iodide for high-performance perovskite solar cells based on NiOx hole transporting materials

Ultra-smooth CsPbI2Br film via programmable crystallization process for high-efficiency inorganic perovskite solar cells

Pristine inorganic nickel oxide as desirable hole transporting material for efficient quasi two-dimensional perovskite solar cells