Enhanced Crystallinity of Low‐Temperature Solution‐Processed SnO₂ for Highly Reproducible Planar Perovskite Solar Cells

Abstract

Low-temperature solution-processed SnO as a promising electron-transport material for planar perovskite solar cells (PSCs) has attracted particular attention because of its outstanding properties such as high optical transparency or high electron mobility. However, low-temperature sol-gel processes used in the synthesis are inevitably affected by the humidity of the atmosphere, which results in a wide distribution in the performance of the prepared PSCs owing to the inability to control crystallinity and defects. Herein, a highly crystalline SnO film is synthesized using a simple water bath post-treatment, which can remove the surface residuals of SnCl on the SnO films, which is beneficial for the interface charge transport from the perovskite to the SnO electron-transport layer. An improved performance of the PSCs can be easily obtained applying this treatment, giving rise to a high power conversion efficiency (PCE) of 19.17 %, much higher than that of the pristine SnO -based device (17.59 %). Most importantly, the reproducibility of the devices has been greatly improved, independent of the environmental humidity. Therefore, the enhanced crystallinity of SnO has shown promise for future commercial PSC applications: 5 cm×5 cm PSC modules have achieved a PCE of 16.16 %.

Room-temperature synthesized SnO2 electron transport layers for efficient perovskite solar cells

“…The residual Cl À on the surface leads to partial decomposition of perovskite. 26 The XRD of the perovskites validates the PbI 2 existence (Fig. S2d †).…”

“…[13][14][15][16][17] Among the candidates, SnO 2 exhibits salient features, such as wide optical band gap (3.6-4.0 eV), good transparency, high mobility up to 240 cm 2 V À1 s À1 , excellent chemical stability, and easy lowtemperature preparation. [18][19][20] There have been many reported processes for preparing SnO 2 ETLs, embracing spin-coating, [21][22][23][24][25][26] slot die coating, 27 atomic layer deposition, 28,29 chemical bath deposition, 30,31 sol-gel method, [32][33][34] etc. Besides, all methods above require a proper temperature treatment in the fabrication process or post-treatment, and sometimes even involve a high temperature annealing.…”

High performance perovskite sub-module with sputtered SnO2 electron transport layer

“…There is also exclusive superiority for PSC in tandem solar cells (Leijtens et al, 2018;Zhao et al, 2018a;Albrecht et al, 2016;, semitransparent solar cells (Xue et al, 2018;Zhang et al, 2018;Xie et al, 2018), and flexible devices (Feng et al, 2018;Bu et al, 2018). However, the instability of perovskite absorber materials (Correa-Baena et al, 2017) and difficulty in large area fabrication devices (Li et al, 2018b) is still serious problems for future commercialization of p e r o v s k i t e -b a s e d s o l a r c e l l . So far, the planar n-i-p structured PSCs (Halvani Anaraki et al, 2018;Yang et al, 2018a) shows great promise due to their easier upscaling deposition of electron transport layers (ETLs) compared to mesostructured PSCs (Petrović et al, 2017).…”

“…And there are lots of fabrication methods (Chen et al, 2019) have been reported to efficiently deposit thin ETL films, however, not all the methods are suitable for achieving uniform large area high quality thin films for large area perovskite solar modules (PSMs). For example, solution based preparation methods such as spin-coating (Yang et al, 2018b) and chemical bath deposition (Anaraki et al, 2016) suffer from necessary annealing process, and the quality of the sintered films are sensitive to the external environmental conditions including humidity (Li et al, 2018a;Bu et al, 2016), oxygen and, etc., which results in poor reproducibility and is fatal to industrial production. Another widely reported method of atomic layer deposition (Wang et al, 2016;Correa Baena et al, 2015) (ALD) to fabricate ETLs for PSCs exhibits excellent stability and reproducibility, which can be attributed to the homogeneity of monolayer deposition.…”

Perylene Diimide‐Based Electron‐Transporting Material for Perovskite Solar Cells with Undoped Poly(3‐hexylthiophene) as Hole‐Transporting Material

“…The majorityo fh igh-efficiency PVSCsr eported so far have utilized the conventional n-i-p device configurationw ith titanium dioxide (TiO 2 )o rs tannic oxide (SnO 2 )a sE TLs. [18][19][20] However,t he preparation of those inorganic n-type semiconducting metal oxide ETLs involves high-temperature sintering, especially fort he mesoporousT iO 2 scaffold, whichr equires more than 450 8Ct os inter. [21,22] This has negative effects on mass production and flexible device architecture.…”