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device stability. [3][4][5][6][7] Moreover, noble metal electrodes could increase the production costs. [8] Therefore, carbon-based inorganic PSCs (C-IPSCs) with a simple HTL-free architecture have attracted extensive attention, in view of their low costs, simple fabrication process, and excellent long-term stability. [5,9,10] Mixed-halide CsPbI 2 Br perovskite is an appealing photovoltaic material due to its good trade-off between band gap (E g ) and phase stability. [11,12] However, the PCEs of reported CsPbI 2 Br C-IPSCs are still far from their counterparts based on the organic HTLs and noble metal electrodes owing to bulk defects and interfacial energy level mismatch. [5] To address these issues, composition and additive engineering have been widely used to optimize perovskite quality and passivate film defects. [13][14][15][16] Besides, some functional materials are also employed as the interlayers to adjust the energy level alignment of CsPbI 2 Br/carbon interface. [10,[17][18][19] Unfortunately, the above studies mainly focus on the perovskite or its top interface modification, while ignoring the electron transport layer (ETL)/CsPbI 2 Br buried interface. Actually, the defects at the bottom interface is even higher than that on top, due to the accumulation of deep level defects, which will cause poor electron transport and severe ion migration, resulting in current density-voltage (J-V) hysteresis and device instability issues. [8,11,20,21] Regarding the typical ETLs such as tin oxide (SnO 2 ) and titanium oxide (TiO 2 ) nanoparticles, up to 30% of the atomic bonds are dangling bonds, which will cause a large number of oxygen defects (O defects ) including oxygen vacancies (O v ) and surface hydroxyl (OH) groups defects (O OH )). [11,22,23] Meanwhile, these dangling states are considered fatal, because the imperfect lattice arrangements can damage its electronic properties, resulting in charge recombination and energy level mismatch with perovskite films. [11,21] On the other hand, interfacial strain and lattice distortion are inevitable during the rapid crystallization process of perovskite films, which have a significant effect on the defect formation energy, carrier mobility, energy level structure, and ion migration. [24,25] Simultaneously, the interfacial residual stress at the bottom of perovskite films is also the reason for accelerated material degeneration. [26] On account of The charge recombination resulting from bulk defects and interfacial energy level mismatch hinders the improvement of the power conversion efficiency (PCE) and stability of carbon-based inorganic perovskite solar cells (C-IPSCs).Herein, a series of small molecules including ethylenediaminetetraacetic acid (EDTA) and its derivatives (EDTA-Na and EDTA-K) are studied to functionalize the zinc oxide (ZnO) interlayers at the SnO 2 /CsPbI 2 Br buried interface to boost the photovoltaic performance of low-temperature C-IPSCs. This strategy can simultaneously passivate defects in ZnO and perovskite films, adjust interfacial energy ...

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Carbon-based CsPbI2Br perovskite solar cells (PSCs) have attracted widespread attention due to their low costs and superior thermal stability. Unfortunately, the bulk defects and interfacial energy level mismatch limit the...

Buried interface modification is promising for preparing high-performance perovskite solar cells (PSCs) by improving the film quality and adjusting the interfacial energy level alignment. In this work, multifunctional ethylenediaminetetraacetic acid diammonium (EAD)-modulated ZnO is employed as an effective buried interface to regulate the interplay between SnO2 and CsPbI2Br in carbon-based inorganic PSCs (C-IPSCs). The burying of EAD into the ZnO interlayer not only enhances the photoelectric properties of ZnO by passivating oxygen defects but also adjusts the energy level alignment of the buried interface. More importantly, the perovskite quality is optimized and the buried interface defects are passivated due to the formation of coordination and hydrogen bondings. Benefiting from such a robust and efficient charge transfer configuration, a maximum power conversion efficiency of 14.58% is achieved in the optimized device, which represents the highest performance reported among those of low-temperature CsPbI2Br C-IPSCs. In addition, the unencapsulated device demonstrates better long-term and thermal stability.

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.