Flexible perovskite solar cells (PSCs) have great potential for portable electronics, however, suffer from large hysteresis in regular structure. Insufficient charge extraction in commonly used tin dioxide (SnO 2 ) electron transporting layer (ETL) is regarded as one possible origin of hysteresis due to the low crystallinity and energy level mismatching. Here, the hysteresis of flexible PSCs is suppressed by synthesizing cobalt-modified SnO 2 ETLs, which improve electron extraction capability due to the high carrier mobility and well-aligned energy levels. Moreover, cobalt modification passivates the defects on the ETL surface, facilitates sequential perovskite film growth, and inhibits carrier recombination. As a result, flexible PSCs with efficiencies exceeding 20% are obtained with significantly reduced hysteresis and enhanced illumination stability. Comprehensive optoelectronic simulations are conducted to unveil the deep mechanisms of eliminated hysteresis. The proposed work provides an efficient and facile strategy for the fabrication of high-performance flexible PSCs upon future commercialization.

Lead leakage from perovskite solar cells (PSCs) leads to device failure and environment contamination. Here, these issues are solved with a sodium phosphate (Na3PO4)‐modified tin(IV) dioxide (SnO2) layer that simultaneously boosts the device performance and captures most of dissolved lead in water. Phosphate incorporation improves charge transfers and passivates the buried perovskite interface, leading to highly improved device efficiency up to 23% with negligible hysteresis. More importantly, the phosphatized SnO2 layer shows high lead‐adsorption capacity with a sequestration efficiency of 79.6% due to the numerous anchor sites of oxygen lone pairs, converting dissolved lead into insoluble compounds in water. This study presents a facile protocol of efficient and sustainable perovskite photovoltaics upon future commercialization.

The hysteresis effect is a critical factor affecting the widespread application of perovskite solar cells (PSCs). To eliminate this adverse effect, it is necessary to uncover the underlying physics, which characterize the microscopic behaviors of electrons, holes, and ions within PSCs. Herein, addressing the hysteresis effect of PSCs, the migration mechanisms of mobile ions (i.e., anions and cations) within the perovskite layer is explored, the simulation model is developed, and the corresponding experiments are performed. The electromagnetic response, the transport of electrons, holes, anions, and cations, and the electrostatic characteristics determined by the charges are considered in detail. The simulation verifies that the performance degradation is indeed originating from the mobile ions, especially under a high ion concentration. The physical reason of the unbalanced performance under forward and reverse electric scans is presented by optoelectronic simulation. The manipulation of the hysteresis effect increasing the built‐in electric field and reducing the hysteresis index (HI) of low ion concentration devices, but increased HI under a high ion concentration is further investigated. The simulation guides the fabrication of a normal‐bandgap PSC, which achieves the reverse (forward) power‐conversion efficiency up to 23.35% (22.22%) with a HI as low as 4.8%.

Color-rendering manipulation of solar cells is drawing increasing interest, since the integration of color displaying can promote various advanced applications. However, the dual functionality of high-performance operation and easy processing remain a challenge. Here we propose a colorful perovskite solar cell (PSC) based on purely planar layers. The photonic crystal (PC), which does not interfere with the PSC processing, enables the display of high-purity colors and maintaining the number of PC layers at 4–6. The fabricated PSC with a four-layer PC successfully displays red-green-blue (RGB) colors, with the power-conversion efficiency of 10.94%, 11.01%, and 13.70%, respectively. Further study indicates that by employing a six-layer PC the PSC can obtain excellent color-displaying effect with the color gamut up to 81.8% of the standard RGB. It also shows that the design has a good tolerance to the deviation of layer thickness.

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