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Efficient electron transport layer-free perovskite solar cells (ETL-free PSCs) are promising designs because they offer low-cost, simpler device configuration and greatly promote the large area flexible application of PSCs. Meanwhile, compared to traditional PSCs with ETL, the development of ETL-free PSCs is hindered by their low performance due to serious interfacial energy loss. Herein, we reveal that ETL-free devices with relatively low carrier lifetimes of perovskite films exhibit more substantial photogenerated carrier loss, resulting in a lower electron-injection rate at the FTO (fluorine-containing tin oxide)/perovskite interface, which is mainly responsible for the performance loss. Moreover, we demonstrate that improving the carrier lifetimes of perovskite films can remedy the poor carrier extraction efficiency at the FTO/perovskite interface through three typical perovskite films. Similarly, for all-inorganic perovskite with lower carrier lifetime and hole transport layer-free devices, prolonging carrier lifetime may be an important measure to improve the device performance. Benefiting from this discovery, increasing the carrier lifetime of the perovskite films can counterbalance the inferior device interfaces, endowing the ETL-free PSCs with high performance close to that of the ETL devices. Our research provides insights into ETL-free PSCs and offers opportunities for high-performance ETL-free PSC device design. [ABSTRACT FROM AUTHOR]

In inverted perovskite solar cells, the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/Ag back interface is quite important because serious recombination occurs and H2O/O2 directly attacks this interface to induce device instability. Here, bi-functional dipole layers are applied at the interface aiming at improving the charge transport and device stability simultaneously. Silane with -CF3 end group anchored on the PCBM surface induces more effective dipole effect than that with (CH2)7-CH3 end functional silane, bending the interface energy level to promote electron transport and reduce recombination. The hydrophobic nature of -CF3 also enhances the durability of the device. This work highlights the back surface dipole management method to achieve efficient and stable perovskite solar cells. [ABSTRACT FROM AUTHOR]