Bilateral Chemical Linking at NiOx Buried Interface Enables Efficient and Stable Inverted Perovskite Solar Cells and Modules.

Inverted NiOx-based perovskite solar cells (PSCs) exhibit considerable potential because of their low-temperature processing and outstanding excellent stability, while is challenged by the carriers transfer at buried interface owing to the inherent low carrier mobility and abundant surface defects that directly deteriorates the overall device fill factor. Present work demonstrates a chemical linker with the capability of simultaneously grasping NiOx and perovskite crystals by forming a Ni-S-Pb bridge at buried interface to significantly boost the carriers transfer, based on a rationally selected molecule of 1,3-dimethyl-benzoimidazol-2-thione (NCS). The constructed buried interface not only reduces the pinholes and needle-like residual PbI2 at the buried interface, but also deepens the work function and valence band maximum positions of NiOx, resulting in a smaller VBM offset between NiOx and perovskite film. Consequently, the modulated PSCs achieved a high fill factor up to 86.24 %, which is as far as we know the highest value in records of NiOx-based inverted PSCs. The NCS custom-tailored PSCs and minimodules (active area of 18 cm2) exhibited a champion efficiency of 25.05 % and 21.16 %, respectively. The unencapsulated devices remains over 90 % of their initial efficiency at maximum power point under continuous illumination for 1700 hours.

Phase control of quasi-2D perovskite thin films by adding MAPbI3 in the precursor solution.

Quasi two-dimensional (Q-2D) perovskite cells have attracted much attention due to their excellent stability compared to their 3D counterparts. However, the Q-2D perovskite thin films prepared by the solution method have been confirmed to be a mixture of small-n phases and large-n phases instead of a pure phase, where the amount and distribution of these phases have a great significance on the performance of Q-2D perovskite solar cells. Here, commercialized 3D perovskite powder was simply added to an ACI perovskite precursor solution to get a uniform and closely connected heterostructure in which the large-n phases can work as pathways for charge transfer. The characterization results of the films and devices show that the appropriate amount of MAPbI3 in the precursor solution could distribute the 3D phases homogeneously within the final film to promote the photovoltaic performance of the devices. Consequently, the power conversion efficiency of the Q-2D ACI perovskite solar cell has been increased from 10.4% to 13.82% (with a 32.8% performance improvement).

Effect of guanidinium chloride in eliminating O2 - electron extraction barrier on a SnO2 surface to enhance the efficiency of perovskite solar cells.

Owing to their low cost, easy fabrication and excellent chemical stability properties, tin dioxide (SnO2) nanoparticles have been widely employed as an electron transfer material in many high-efficiency perovskite solar cells (PeSCs). However, the adsorbed oxygen species (i.e. O2 -) on the surface of the SnO2 layer, which are induced by the annealing process under ambient environment, have always been overlooked. In general, the adsorption of oxygen creates an energy barrier at the SnO2/perovskite interface, impairing the efficiency of PeSCs. In this work, by using guanidinium (GA) chloride to modify the SnO2 surface, we have successfully improved the power conversion efficiency (PCE) of PeSCs from 15.33% (no GA-modification) to 18.46%, with a maximum fill factor of 80%. The performance enhancement is mainly attributed to the reduced energy barrier at the SnO2/perovskite interface due to the strong coupling between the GA and the adsorbed oxygen, which has been supported by the FTIR and XPS results. The strategy of reducing the charge extraction barrier by GA modification has been demonstrated to be an efficient approach to improve both the PCE and stability.