Precursor Engineering of the Electron Transport Layer for Application in High‐Performance Perovskite Solar Cells

Abstract

The electron transport layer (ETL) is a key component of regular perovskite solar cells to promote the overall charge extraction efficiency and tune the crystallinity of the perovskite layer for better device performance. The authors present a novel protocol of ETL engineering by incorporating a composition of the perovskite precursor, methylammonium chloride (MACl), or formamidine chloride (FACl), into SnO 2 layers, which are then converted into the crystal nuclei of perovskites by reaction with PbI 2 . The SnO 2 -embedded nuclei remarkably improve the morphology and crystallinity of the optically active perovskite layers. The improved ETL-to-perovskite electrical contact and dense packing of large-grained perovskites enhance the carrier mobility and suppress charge recombination. The power conversion efficiency increases from 20.12% (blank device) to 21.87% (21.72%) for devices with MACl (FACl) as an ETL dopant. Moreover, all the precursor-engineered cells exhibit a record-high fill factor (82%).

Record‐Efficiency Flexible Perovskite Solar Cells Enabled by Multifunctional Organic Ions Interface Passivation

“…[42] For the HADI-SnO 2 film, the N1 peak was weakened and exhibited a large shift, indicating a strong interaction between tail NH 3 and SnO 2 , probably because the H of the tail NH 3 units interacts with OH groups on the surface of the SnO 2 to form H 2 O that is released to the environment during the thermal annealing. [31] Compared with the obvious movement of the N1 peak in the HADI-SnO 2 film, the N1 peak at 398.90 eV and the N2 peak at 400.42 eV have no shift for the HADI-PbI 2 film (Figure 2d), while the N3 peak at 401.10 eV moved to 401.46 eV and became flat and broad, which indicates that the CN in the imidazolium unit has a stronger ability to bind with undercoordinated Pb 2+ than tail NH 3 through Lewis acid/base interaction. This coincides well with the reported result that the imidazole unit has a higher binding energy with Pb 2+ in contrast to the NH 2 unit.…”

“…[30] Lin's group presented a novel SnO 2 ETL by incorporating methylammonium chloride (MACl) or formamidine chloride (FACl); the ammonium salt is then converted into crystal nuclei of perovskite by reaction with PbI 2 , and the subsequently formed perovskite layer has remarkably improved morphology and crystallinity. [31] The device with MACl-doped SnO 2 delivers a PCE of 21.87%. Although the above ammonium salts could heal the defects of SnO 2 , the obtained products from the interaction between these ammonium salts and SnO 2 cannot further modify the top perovskite layer but are instead released into the environment as gas (e.g., NH 3 , N(CH 3 ) 3 , CH 3 NH 2 , H 2 O, HCl, etc.).…”

Electron Transport Assisted by Transparent Conductive Oxide Elements in Perovskite Solar Cells

“…This suggests that modifying the InF 3 promotes the growth of perovskite films. [11,32,42] Figure 3c,d show the cross-sectional SEM images of the PSCs based on unmodified SnO 2 and InF 3 À SnO 2 ETLs. The perovskite particles deposited on the unmodified SnO 2 ETL are disoriented, whereas the perovskite particles grown on the InF 3 À SnO 2 ETL grow perpendicular to the substrate surface and connect the ETL with the hole transport layer (HTL), which facilitates charge transfer.…”

“…[22][23][24][25][26][27][28][29][30] Most importantly, the highperformance SnO 2 ETL can be prepared at low temperature, suggesting its immense potential as ETL in PSCs. [31][32][33][34][35][36][37] Transparent conductive oxides (TCOs) are indispensable components of PSCs. Some common TCOs are F-doped SnO 2 (FTO) and Sn-doped In 2 O 3 (ITO).…”

Bifunctional Interfacial Regulation with 4‐(Trifluoromethyl) Benzoic Acid to Reduce the Photovoltage Deficit of MAPbI3‐Based Perovskite Solar Cells

“…Material bandgaps, [8,9] perovskite absorption film crystallinity, [10] defects in the bulk film and interfaces, [11] and electron/hole pair extraction and transportation efficiency [12] all significantly influence the performance of PSCs. In particular, interfacial properties affect the performance of integral PSCs.…”