Efficient and Stable Tin Perovskite Solar Cells Enabled by Graded Heterostructure of Light‐Absorbing Layer

Abstract

Lead‐free tin perovskite solar cells (TPSCs) have attracted widespread attention in recent years due to their low toxicity, suitable bandgap, and high carrier mobility. However, the photovoltage and efficiency of TPSCs are still much lower than those of the lead counterparts because of the high trap density and unfavorable band structure in tin perovskite films. To overcome these issues, efficient and stable TPSCs with a graded heterostructure of light‐absorbing layer are reported, in which the narrow‐bandgap tin perovskite dominates at the bulk, whereas the wide‐bandgap tin perovskite is distributed with a gradient from bulk to surface. This heterostructure can selectively extract the photogenerated charge carriers at the perovskite/electron transport layer interface, reduce the density of trap states, and impede the oxidation process of Sn2+ to Sn4+ in air. As a consequence, this graded heterostructure of tin perovskite layer contributes to an increase of 120 mV in the open‐circuit voltage and a maximum power conversion efficiency of 11% for TPSCs with longer operational stability.

Additive Engineering toward High‐Performance Tin Perovskite Solar Cells

“…The tin halide perovskites show a similar crystal structure with that of the lead perovskites with an ABX 3 lattice. The A‐site cations dominate at the cubic vacancy of the corner‐sharing frameworks, [ 49 ] while the B‐site metallic cations fill the octahedral cavity, which are enveloped by the X‐site anions. For a typical tin perovskite structure (ASnX 3 ), methylammonium (MA + ), formamidinium (FA + ), and cesium (Cs + ) have been reported as the A‐site cations.…”

“…[ 82 ] This wide‐bandgap 2D phase on tin perovskite surface could also serve as passivation agents to increase the open‐circuit voltage ( V OC ) of tin PSCs. [ 49 ] Chemical structures of the reported monovalent organic ammoniums are shown in Figure .…”

Suppression of Nonradiative Recombination by Vacuum‐Assisted Process for Efficient Lead‐Free Tin Perovskite Solar Cells

“…[12,13] Additionally, the bandgaps of Pb-based perovskites (≈1.55 eV) are far from ideal (≈1.4 eV), which theoretically limits the highest achievable PCE. [14] Thus, fast development of low-toxicity Pb-free and bandgap-suitable PVSCs is in high demand.Various alternative metal elements to Pb, such as tin (Sn), [15,16] germanium (Ge), [17] bismuth (Bi), [18] and antimony (Sb), [19] etc., have been explored. Among them, Pb-free Sn-based perovskites have been regarded as the most promising candidate due to their lower toxicity and superior optoelectrical properties.…”

“…Various alternative metal elements to Pb, such as tin (Sn), [15,16] germanium (Ge), [17] bismuth (Bi), [18] and antimony (Sb), [19] etc., have been explored. Among them, Pb-free Sn-based perovskites have been regarded as the most promising candidate due to their lower toxicity and superior optoelectrical properties.…”

Low‐Dimensional Inorganic Tin Perovskite Solar Cells Prepared by Templated Growth

“…In recent years, the fabrication and inclusion of lowdimensional structure significantly prompted the efficiency and stability development of organic-inorganic hybrid tin perovskite solar cells (TPSCs). [8] The exploration of lowdimensional inorganic tin perovskite with high lattice energy presents another opportunity to further improve the stability and efficiency of TPSCs. [9] Recently, the efficiencies of allinorganic CsSnI 3 perovskite solar cells based on both thermal evaporation and solution process are significantly enhanced.…”