Organic‐Free and Lead‐Free Perovskite Solar Cells with Efficiency over 11%

Abstract

photovoltaic devices (23.3%), showing great potential toward practical applications. [1] However, thermal instability of organic components (e.g., methylammonium (MA) and formamidinium (FA)) and high toxicity of heavy metal lead (Pb) pose challenges for practical applications. [2][3][4][5] To address these issues, a new perovskite family of organic-free and lead-free cesium tin tri-iodide (CsSnI 3 ) has been proposed and attracted considerable attention. [6][7][8] One of the potential candidates within the new perovskite family is the inorganic CsSnI 3 . This kind of perovskite possesses favorable direct bandgap (around 1.3 eV), high optical absorption coefficient (about 10 4 cm −1 in the visible range), and ultralow exciton binding energy (18 meV), making it very promising as a photoactive layer for PSCs' construction. [9][10][11] Since the first report in 2014 by Kumar et al., the efficiency of CsSnI 3based perovskite solar cells has witnessed steady improvement from 2.02% to 10.1% in 2021. [12,13] Such development has mainly been attributed to addressing the factors that affect the performance of the devices, such as annealing temperature, [14] film fabrication method, [15] and interface regulation. [16,17] However, little efforts have been made to Organic-free and lead-free CsSnI 3 perovskite solar cells (PSCs) have recently gained growing attention as a promising template to mitigate the thermal instability and lead toxicity of hybrid lead-based PSCs. However, the relatively low device efficiency due to the high content of Sn(II)-related defects hinders its further development. Herein, highly performed CsSnI 3−x Br x compositional perovskite-based PSCs are achieved by using dimethyl ketoxime (C 3 H 7 NO, DMKO) as a multifunctional additive. As a commercially used deoxidant, DMKO can effectively neutralize the oxygen molecule and reduce Sn 4+ back to Sn 2+ , enhancing the oxidation resistance of the film. Besides, the electron-rich oxime group (NOH) in DMKO tends to interact with Sn 2+ ions with extremely low adsorption energy less than −15 eV and inhibits defect formation, resulting in films with low defect density. The corresponding PSCs deliver a considerable open-circuit voltage (V oc ) of 0.75 V with a record efficiency as high as 11.2%, which represents the highest reported efficiency for lead-free all-inorganic PSCs thus far. More importantly, the grain surface distributed DMKO provides an in situ encapsulation of the perovskite, which results in greatly enhanced ambient stability of the un-encapsulated devices.

Halide Chemistry in Tin Perovskite Optoelectronics: Bottlenecks and Opportunities

“…Chemie beneficial to the operational stability of Sn HaP solar cells, further research in this direction is needed. We expect these approaches to boost hole extraction in archetypal Sn HaP device architectures based on PEDOT:PSS and other less commonly employed HTLs such as nickel oxide (NiO x ) [83] or ambipolar tin oxide (SnO x ). [84] Recently, Song et al demonstrated the use of self-assembled monolayers (SAMs) on indium tin oxide (ITO) anodes in p-i-n, FASnI 3 -based solar cells.…”

Halide Chemistry in Tin Perovskite Optoelectronics: Bottlenecks and Opportunities

“…beneficial to the operational stability of Sn HaP solar cells, further research in this direction is needed. We expect these approaches to boost hole extraction in archetypal Sn HaP device architectures based on PEDOT:PSS and other less commonly employed HTLs such as nickel oxide (NiO x ) [83] or ambipolar tin oxide (SnO x ). [84] Recently, Song et al demonstrated the use of self-assembled monolayers (SAMs) on indium tin oxide (ITO) anodes in p-i-n, FASnI 3 -based solar cells.…”

Comparative Study of the Correlation between Diffusion Length of Charge Carriers and the Performance of CsSnGeI3 Perovskite Solar Cells

“…In particular, Sn-based perovskite materials have been attracting a lot of interest since they share many of the same features as the other options and have shown the most promise in terms of device performance. − The direct band gaps of these perovskites are significantly smaller and more appealing than those of their Pb-based counterparts, ranging from around 1.2–1.4 eV. , These perovskites exhibit direct band gaps between 1.2 and 1.4 eV, which are significantly smaller and more desirable than their Pb-based counterparts. Also, the all-inorganic Pb-free cesium tin triiodide (CsSnI 3 ) perovskite is currently the best candidate owing to its enhanced optoelectronic features, making it a potential alternative to Pb-based light absorption perovskites. , Substituting Cs for the organic cation in the perovskites has been shown to greatly improve their thermal stability and ambient cell performance .…”

“…23−25 The direct band gaps of these perovskites are significantly smaller and more appealing than those of their Pb-based counterparts, ranging from around 1.2−1.4 eV. 26,27 These perovskites exhibit direct band gaps between 1.2 and 1.4 eV, which are significantly smaller and more desirable than their Pb-based counterparts. Also, the allinorganic Pb-free cesium tin triiodide (CsSnI 3 ) perovskite is currently the best candidate owing to its enhanced optoelectronic features, making it a potential alternative to Pb-based light absorption perovskites.…”