Management of the crystallization in two-dimensional perovskite solar cells with enhanced efficiency within a wide temperature range and high stability

Control over the crystallization in quantum well Ruddlesden-Popper phase halide perovskites is vitally important for the photovoltaic performance. Through managing the molecular stacking in 2-dimentioanl BA ₂ MA ₃ Pb ₄ I ₁₃ (n = 4) perovskites based on PTAA hole transporting layers, we achieve enhanced vertical crystal orientations in BA ₂ MA ₃ Pb ₄ I ₁₃ polycrystalline films, leading to a champion power conversion efficiency (PCE) of 14.3% (n ≤ 4) with negligible hysteresis in PTAA based p-i-n perovskite solar cells. The enhanced PCE is ascribed to the suppression on change recombination associated with an expedited charge extraction, revealed by transient opto-electrical analyses. Benefitted from the enhanced molecular arrangement revealed by GIWAXS, efficient charge generation at low temperatures (T) is enabled, leading to a negative T-dependence of efficiency in the hot-cast device, showing a peak PCE of 15.0% at 210 K. This trend is likely correlated to the reduced potential barriers in the quantum wells with which the detrapping of photo-carriers is facilitated at smaller thermal energy. Contrastingly, the solar cells with more randomly oriented crystals are found to suffer more from these unfavorable barriers, resulting in decreased PCEs with lowered T. Our findings highlight the opportunity through crystallization management coupled with interface engineering to achieve high efficiency and stable 2D perovskite solar cells within a wide T-window.