PbI₂–HMPA Complex Pretreatment for Highly Reproducible and Efficient CH₃NH₃PbI₃ Perovskite Solar Cells

Abstract

Interfacial engineering of the meso-TiO surface through a modified sequential deposition procedure involving a novel PbI-HMPA complex pretreatment is conducted as a reproducible method for preparing MAPbI based perovskite solar cells providing the highest efficiencies yet reported with the polymer HTM layer. Grazing-incidence X-ray diffraction depth profiling confirms the formation of a perovskite film with a PbI-rich region close to the electron transport layer (ETL) due to the strong interaction of HMPA with PbI, which successfully retarded the dissolution of the PbI phase when depositing the perovskite layer on top. These results are further confirmed by energy-dispersive X-ray spectroscopy performed in a scanning transmission electron microscope, which reveals that the I/Pb ratio in samples treated with the complex is indeed reduced in the vicinity of the ETL contact when compared to samples without the treatment. The engineered interface leads to an average power conversion efficiency of 19.2% (reverse scan, standard deviation SD < 0.2) over 30 cells (best cell at 19.5% with high FF of 0.80).

Alkali Metal Doping for Improved CH3NH3PbI3 Perovskite Solar Cells

“…In this regard, combination of solvent and dopants have been tested, such as: the introduction of different source of metal or the solvent, the utilization of single or mixed solvent,19, 20 a variety of lead salt precursors,21, 22 as well as so‐called engineering step23 or the exotic additive: ionic liquid,24 Lewis base25, 26, 27 or other organic and inorganic additives (MACl,28 Guanidinium,29 water,30, 31 H 3 PO 2 ,32, 33 1,8‐diiodooctane (DIO),34 1‐chloronaphthalene (CN),35 hydroiodic acid (HI),36, 37 aluminum acetylacetonate (Al‐acac 3 ),38 LiI,39 Na + 40 etc. ), which induce the nucleation and crystallization process of perovskite thin films.…”

Trash into Treasure: δ‐FAPbI3 Polymorph Stabilized MAPbI3 Perovskite with Power Conversion Efficiency beyond 21%

“…There are two main categories of materials that can be used for this purpose. The first one is extrinsic materials such as PbI 2 , polymers, fullerene derivatives, Al 2 O 3 , surfactant, and amino acids . The other one is 2D/3D mixed multi‐dimensional (MD) hybrid perovskites .…”

Development of electron and hole selective contact materials for perovskite solar cells

“…4) [41]. The highest PCE with this combination was achieved by Nazeeruddin group as 19.5% [34]. In 2014, Seok and coworkers recorded the highest certified PCE (16.2%) employing PTAA as the HSM [9]; an even higher certified PCE of 17.9% has also been demonstrated [54].…”

“…It was supposed that the effective n-doping may be due to under-coordinated halides acting as shallow electron donors on the crystal surface, or due to a surface charge effect of the mesoporous metal oxide. Nazeeruddin group recently found by FIB-EDX analysis in a cross section of perovskite solar cell the non-uniform distribution of iodine element from mesoporous layer to capping layer [34].…”

“…From this study, Ito and coworkers believe that the light degradation takes place at the TiO2/CH3NH3PbI3 interface. Another effective way of controlling the charge recombination is to introduce some wide band gap semiconductors at the TiO2 surface like PbI2 [34], MgO [92], Y2O3 and Al2O3 [93] passivation. For example, an ultrathin MgO nanolayer can be introduced to the interface between the TiO2 layer and perovskite layer.…”