We propose that 1 + 1 + 1 triple-junction solar cells can provide an increased efficiency, as well as a higher open circuit voltage, compared to tandem solar cells.

Recent advances on passivation and morphology engineering approaches adopted to obtain high efficiency and stability in perovskite solar cells are thoroughly reviewed.

Hybrid halide perovskite solar cells were first demonstrated in 2009 with cell efficiency quickly soaring from below 10% to more than 23% in a few years. Halide perovskites have the desirable processing simplicity but are very fragile when exposed to water and heat. This fragility represents a great challenge for the achievement of their full practical potential in photovoltaic technologies. To address this problem, here we review the recent development of the mixed-dimensional perovskites, whereby the trade-off between power conversion efficiency and stability of the material can be finely tuned using organic amine cations with different sizes and functionalities.