Efficient Passivation Strategy on Sn Related Defects for High Performance All‐Inorganic CsSnI₃ Perovskite Solar Cells

Abstract

Despite remarkable progress in hybrid perovskite solar cells (PSCs), the concern of toxic lead ions remains a major hurdle in the path towards PSC's commercialization; tin (Sn)‐based PSCs outperform the reported Pb‐free perovskites in terms of photovoltaic performance. However, it is of a particularly great challenge to develop effective passivation strategies to suppress Sn(II) induced defect densities and oxidation for attaining high‐performance all‐inorganic CsSnI3 PSCs. Herein, a facile yet effective thioamides passivation strategy to modulate defect state density at surfaces and grain boundaries in CsSnI3 perovskites is reported. The thiosemicarbazide (TSC) with SCN functional groups can make strong coordination interaction with charge defects, leading to enhanced electron cloud density around defects and increased vacancy formation energies. Importantly, the surface passivation can reduce the deep level trap state defect density originated from undercoordinated Sn2+ ion and Sn2+ oxidation, significantly restraining nonradiative recombination and elongating the carrier lifetime of TSC treated CsSnI3 PSCs. The surface passivated all‐inorganic CsSnI3 PSCs based on an inverted configuration delivers a champion power conversion efficiency (PCE) of 8.20%, with a prolonged lifetime over 90% of initial PCE, after 500 h of continuous illumination. The present strategy sheds light on surface defect passivation for achieving highly efficient all‐inorganic lead‐free Sn‐based PSCs.

Fully Inorganic CsSnI3 Mesoporous Perovskite Solar Cells with High Efficiency and Stability via Coadditive Engineering

“…As the vibrational frequency is proportional to the square root of the force constant in the harmonic motion of the diatomic model, the reduction in the vibration of the Lewis base (amino group) signifies the bond strength between the amino group (nitrogen), and carbon decreases upon the formation of APZ and Sn 4+ , suggesting a strong Lewis acid–base addition reaction between CsSnI 3 perovskite compound and the amino group of APZ (Figure 2a). [ 32 ] We first stored unencapsulated CsSnI 3 films without and with APZ addition in ambient environment at disparate times to certify the impact of APZ on inhibiting Sn 2+ oxidation. As shown in Figure S7, Supporting Information, the CsSnI 3 film with APZ nearly kept its initial color (black) after 3 h of exposure to ambient air and turned into yellow slightly after 6 h, whereas the film without APZ became yellow completely after 6 h of exposure to ambient air.…”

Enhanced Stability of Tin Halide Perovskite Photovoltaics Using a Bathocuproine—Copper Top Electrode

“…Despite the aforementioned advantages there are very few reports pertain to use of Cu as the top contact in perovskite PVs. [18,20,21,[25][26][27][28][29] Those that do show that the initial performance is comparable to that using a Ag electrode [21] and that the device shelf-life can exceed that of identical devices using a Ag electrode, [18] although initial device performance is rarely a good indicator of stabilized device performance under continuous illumination and load. Similarly a long shelf-life does not necessarily translate to high operational stability, since some degradation mechanisms of metal halide perovskites are light and heat and electric field induced and/or accelerated.…”

“…However, such accelerated tests are useful because they help researchers to quickly identify promising materials and device designs for long-life applications such as PVs. Without device encapsulation wholly inorganic tin perovskites have proved to be the most stable type of tin perovskite PV when tested in ambient air; Table S1, Supporting Information, [28,[31][32][33][34][35][36][37] although it is notable that none of the reports relate to device testing under load. Similar to the case of lead perovskites, the power conversion efficiency of inorganic tin perovskites lags far behind that of organo-tin halide perovskites and so there is a need to find ways to stabilize organo-tin halide perovskites for PV applications.…”

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

“…at GBs would cause nonradiative recombination and cause the loss of photo-generated carriers (Figure 14a), V OC and PCE. [108,168,169] Most importantly, loosely grooved GBs resemble prominent leaching pathways that lead to direct contact between charge transport layers below and above perovskite layers, thus causing small shunt resistances and shortcircuit behaviors in solar cell performance. Therefore, protecting the GBs and passivating defect is particularly important for obtaining high-efficiency and stable PSCs.…”