2D WSe₂ Flakes for Synergistic Modulation of Grain Growth and Charge Transfer in Tin‐Based Perovskite Solar Cells

Abstract

Tin (Sn)‐based perovskites with favorable optoelectronic properties and ideal bandgaps have emerged as promising alternatives to toxic lead (Pb)‐based perovskites for photovoltaic applications. However, it is challenging to obtain high‐quality Sn‐based perovskite films by solution process. Here, liquid‐exfoliated 2D transition‐metal dichalcogenides (i.e., MoS2, WS2, and WSe2) with smooth and defect‐free surfaces are applied as growth templates for spin‐coated FASnI3 perovskite films, leading to van der Waals epitaxial growth of perovskite grains with a growth orientation along (100). The authors find that WSe2 has better energy alignment with FASnI3 than MoS2 and WS2 and results in a cascade band structure in resultant perovskite solar cells (PSCs), which can facilitate hole extraction and suppress interfacial charge recombination in the devices. The WSe2‐modified PSCs show a power conversion efficiency up to 10.47%, which is among the highest efficiency of FASnI3‐based PSCs. The appealing solution phase epitaxial growth of FASnI3 perovskite on 2D WSe2 flakes is expected to find broad applications in optoelectronic devices.

High Open Circuit Voltage Over 1 V Achieved in Tin‐Based Perovskite Solar Cells with a 2D/3D Vertical Heterojunction

“…[6,7] However, the performance of Sn-based PSCs still lags far behind their Pb-based counterparts although the two types of perovskite materials have comparable optoelectronic properties like suitable bandgaps and high enough carrier mobilities for solar cells. [8][9][10] The major drawback of Sn-based PSCs is their low open circuit voltages (V OC ), which are normally between 0.2 and 0.7 V for devices with pure 3D perovskites, [5,[11][12][13][14][15][16][17][18][19] due to high voltage losses induced by fast non-radiative carrier recombination in the Sn-based perovskite materials. [20,21] To the best of our knowledge, the carrier lifetimes in Sn-based perovskites measured by photoluminescence (PL) spectroscopy are only several to tens of nanoseconds, [6,7,[22][23][24] which are much shorter than those of Pb-based perovskites reported in literature.…”

“…The major drawback of Sn‐based PSCs is their low open circuit voltages ( V OC ), which are normally between 0.2 and 0.7 V for devices with pure 3D perovskites, [ 5 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] due to high voltage losses induced by fast non‐radiative carrier recombination in the Sn‐based perovskite materials. [ 20 , 21 ] To the best of our knowledge, the carrier lifetimes in Sn‐based perovskites measured by photoluminescence (PL) spectroscopy are only several to tens of nanoseconds, [ 6 , 7 , 22 , 23 , 24 ] which are much shorter than those of Pb‐based perovskites reported in literature.…”

Advances in Tin(II)‐Based Perovskite Solar Cells: From Material Physics to Device Performance

“…As a result, a PCE of 10.47% was obtained for WSe 2 -modified PSCs, which was among the highest PCE of FASnI 3 -based PSCs. [98] The templated growth method is also used in flexibility PSCs, Chen et al applied graphite phase-C 3 N 4 (g-C 3 N 4 ) into flexible Sn-based PSCs as a crystallization template, which slows crystallization process through size-effect and passivated defects simultaneously (Figure 6c). Consequently, the PSCs achieved a PCE of 8.56% with negligible hysteresis and only lost 9% of their original PCE after 1000 h under N 2 environment [20] (Figure 6d and e).…”

Two-Dimensional Materials for Perovskite Solar Cells with Enhanced Efficiency and Stability

“…Epitaxial growth has been demonstrated to be a favorable technique for preparing perovskite films with preferential orientations on 2D-material-based substrates. Recently, TMDs have been used as substrates for prepared perovskite films through van der Waals epitaxial growth. − Tang et al demonstrated that MAPbI 3 perovskite films were successfully prepared on a MoS 2 -modified poly­(bis­(4-phenyl)­(2,4,6-trimethylphenyl) amine) (PTAA) substrate through solution-phase epitaxial growth. The selected-area electron diffraction (SAED) pattern (Figure a) shows that the perfectly matched (008) plane of MAPbI 3 and the (110) plane of MoS 2 promote preferential orientation along the (110) plane for the growth of perovskite films (Figure b).…”