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Printable hole‐conductor‐free perovskite solar cells (PSCs) have attracted intensive research attention due to their high stability and simple manufacturing process. However, the cells have suffered severe potential loss in the absence of the hole transporting layer. The dimensionality of the perovskite absorber in the mesoporous carbon electrodes by conducting post‐treatments is reduced. The low‐dimensional perovskites possess wide‐bandgaps and form type‐II band alignment, favoring directional charge transportation and thus enhancing the device performance. For the cells using MAPbI3 (MA = methylammonium) as the light absorber, the open‐circuit voltage (VOC) is significantly enhanced from 0.92 to 0.98 V after posttreatment, delivering an overall efficiency of 16.24%. For the cells based on FAPbI3 (FA = formamadinium), a high efficiency of 17.47% is achieved with VOC of 1.02 V, which are both the highest reported values for printable hole‐conductor‐free PSCs. This strategy provides a facile method for tuning the energy level alignment for mesoscopic perovskite‐based optoelectronics. [ABSTRACT FROM AUTHOR]

The low cost and scalability advantages of printable mesoscopic perovskite solar cells (p‐MPSCs) are impaired by the issue of limited power conversion efficiency (PCE). Herein, the PCE of p‐MPSCs is improved by introducing the polymer additive polyacrylonitrile (PAN) into the formamidinium (FA)‐based perovskite for crystallization and defect modulation. PAN forms hydrogen bond and coordination bond with halide perovskite through its C≡N group. Such interactions improve the crystallization and filling of FA‐based perovskite in the mesoscopic scaffold and bring a long carrier lifetime by passivating defects. The synergy improves the PCE of p‐MPSCs from 16.80% to 18.33%. Meanwhile, the hydrophobic nature of PAN enhances the device's resistance against moisture. This work demonstrates that the polymer additive is a promising choice for breaking the PCE limit of p‐MPSCs. [ABSTRACT FROM AUTHOR]

High-performance perovskite solar cell processed in ambient air is a big challenge due to the sensitivity of perovskite films to air. Many defects are generated easily at grain boundaries and in the perovskite films by conventional molecular/ion precursor solution mixing methods (i.e., solution mixing-based method), which restrict its stability in air and photovoltaic performance with most power conversion efficiency less than 15%. In this work, we develop a facile method for air-processed, highly crystalline, quasi-3D perovskite film with large grain size (over 6.6 times bigger than that from control conventional method) and improved ambient air stability by phenylethylammonium (PEA)-doped MA1−xPEAxPbI3 perovskite crystal engineering. Furthermore, benefiting from PEA+ doping and crystal engineering, the trap density decreases 50% compared with control. Consequently, with the optimal concentration of PEA doping, the power conversion efficiency increases from 15.6% for conventional solution mixing-based perovskite solar cells to 17.6% for crystal engineering-based ones with significantly improved moisture stability. The perovskite crystal engineering-based solar cells without any encapsulation retain 75% of the initial performance after 30-day storage in ambient air under a relative humidity of 50 ± 10%, and two times faster degradation rate is observed for control, conventional solution mixing-based perovskite solar cells when compared with crystal engineering-based ones. [ABSTRACT FROM AUTHOR]

Triple‐mesoscopic perovskite solar cells (PSCs) have attracted intensive attention due to the high stability, simple fabrication process, and low material cost. In this structure, the perovskite layer is hosted by a triple‐mesoscopic scaffold of TiO2/ZrO2/carbon, and thus the crystal quality is sensitive to the thermal annealing process. Typically, the annealing process is conducted in a petri dish, for which the solvent evaporation of the perovskite precursor is slowed down, but not controllable and designable. To control the solvent evaporation, annealing chambers are first designed with different shape and vapor releasing channels. Then, physical simulations are performed by a finite element method, and it is found out that the chamber with a crowned top and releasing channels on the bottom sides can realize homogeneous distribution of the solvent vapor. To verify the simulation results, chambers are fabricated by 3D printing technique, for which the printing deviation can be as low as 100 µm. By balancing the solvent evaporation and release, the optimal solvent evaporation is achieved of the perovskite precursor in the triple‐mesoscopic scaffold. This work offers a method to obtain homogeneous distribution of solvent vapor, and provides a new insight into understanding the influence of solvent evaporation during the thermal annealing process for PSCs. [ABSTRACT FROM AUTHOR]