It is well-known that two-dimensional Ruddlesden-Popper (2DRP) perovskite has higher stability than three-dimensional counterparts. However, fundamental issues still exist in the vertical orientation and phase composition as well as phase distribution. Here, obvious control of the film quality of 2DRP PEA2MA4Pb5I16 (n = 5) perovskite is demonstrated via a thermal-pressed (TP) effect. The crystallinity, morphology, phase composition, and optoelectronic features unequivocally illustrate that the TP effect achieves a larger gain size, a smoother surface, an effectively vertical orientation, a relatively pure phase with a large n value, a gradient distribution of quantum wells, and enhanced interlayer interaction. These film and interface features lead to markedly enhanced charge transport/extraction and lower trap density. Accordingly, the TP-based perovskite film device delivers a power conversion efficiency of 15.14%, far higher than that of the control film device (11.10%) because of significant improvements in open-circuit voltage and short-circuit current. More importantly, it also presents excellent hydrophobicity, illumination stability, and environmental stability. In addition, the 2D perovskite self-powered photodetector also exhibits high responsivity (0.25 A W-1) and specific detectivity (1.4 × 1012 Jones) at zero bias.
Keywords: graded-vertical quantum-well distribution; phase composition; solar cells; thermal-pressed effect; two-dimensional perovskites; vertical orientation.