Enhanced Charge Transport via Mixed-Dimensional Heterostructures in 2D–3D Perovskites and Their Relevance to Solar Cells

Abstract

Two-dimensional and three-dimensional (2D−3D) mixed perovskites have shown noteworthy improvements in device performance and stability, owing to their hydrophobic nature and outstanding optoelectronic properties. However, the nature of the mixed-dimensional heterostructure and charge transport in 2D−3D perovskites is not clearly understood. In this study, we elucidate the effect of mixed-dimensional heterostructures on charge transport and their relevance to perovskite solar cells by changing the c o m p o s i t i o n o f 2 D − 3 D m i x e d p e r o v s k i t e s [(BA 2 PbI 4 ) x (MAPbI 3 ) 1−x , BA 2 PbI 4 as a 2D perovskite is added to 3D MAPbI 3 , BA: butylamine, MA: methylammonium]. A small amount of BA 2 PbI 4 (x ≤ 0.02, x: nominal amount) enhances crystallinity by compact grain growth and improves charge transport by passivation of the grain boundary and an increase in conductivity. The trap passivation by sandwich-structured 2D−3D grains enhances the efficiency of the solar cell by 3%, and the mixed perovskite maintains the efficiency for 50 days (80% of the initial value). However, a large amount of 2D perovskite (x > 0.04) reduces the carrier lifetime and impedes charge transport due to poor conductivity. Furthermore, tuning of the 2D−3D perovskites modifies the electrical potential distribution near grain boundaries as well as the work function in perovskite absorbers and eventually alters the recombination of traps. Our study has thereby proven the improvement of charge transport and suggested a way to boost device performance of mixed 2D−3D perovskite solar cells.

Functional 2D Phases in Mixed Dimensional Perovskite Photovoltaics

“…The last sheet of Figure 3a further demonstrates that 2D perovskites (n = 1) are combined into 3D perovskites. [86] Li et al introduced long-chain EDBEPbI 4 (EDBE represents 2,2-(ethylenedioxy)bis-(ethylammonium)) into 3D perovskite to construct 2D/3D vertical heterojunction (Figure 3b), and the exposed amine groups on x (MAPbI 3 ) 1-x near the GBs. Reproduced with permission.…”

“…Whereas, the introduction of excess 2D phases in 3D perovskites reduces the local current at grain boundaries, suggesting that the charge carrier transport is inhibited by the intermediate 2D–3D phases. [ 86 ]…”

“…Whereas, the introduction of excess 2D phases in 3D perovskites reduces the local current at grain boundaries, suggesting that the charge carrier transport is inhibited by the intermediate 2D-3D phases. [86] Under illumination conditions, the 2D/3D carrier transport mechanism has also been explained in detail. Yu et al found that under dark conditions, the presence of interfacial defects leads to partial shielding of the built-in electric field of 2D/3D perovskite heterojunctions, and electrons (and holes) can freely pass through 2D/3D perovskite interface; under illumination, photogenerated carriers fill the interface defect states, and the built-in electric field of the 2D/3D perovskite interface returns to an unshielded state, thereby forming a photogenerated potential barrier, resulting in suppressed photogenerated electrons (and holes) transport.…”

“…a) TEM images(left) and HRTEM images (middle and right) of (BA 2 PbI 4 ) x (MAPbI 3 ) 1-x near the GBs. Reproduced with permission [86]. Copyright 2022, American Chemical Society.…”

Insight into Controlled Surface Passivation of PEDOT:PSS for Defect Density Modulation and Efficient Charge Transport for Perovskite Solar Cells

“…Insights regarding the interfaces between the layers in a device are crucial to improve the performance of the PSC. Efficient charge extraction, , transportation, , and interface recombination , are important for high device efficiency. These parameters depend on the proper choice of ETL and HTL materials and the quality of the device fabrication.…”