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SnO2 compact layer (c‐SnO2) frequently suffers from degradation in high temperature processes (HTP) such as crack, worse interfacial contact, and electrical properties, that is, annealing effect. To solve this problem, a kind of bifunctional SnO2 colloid is developed by using small molecular oxalate whose organic components can be removed clearly at a low temperature process (LTP). The c‐SnO2 and SnO2 mesoporous layer (m‐SnO2) derived from the fresh and aged sols with the same colloid show no annealing effect, decreasing oxygen vacancy, and adsorbing water on increasing annealing temperature. The champion devices of LTP and HTP SnO2 planar perovskite solar cells (PSCs) achieve, respectively, stabilized photoelectric conversion efficiencies (PCEs) of 20.74% and 20.70%. In contrast, the performance of champion devices of their mesoporous counterparts is significantly improved, showing nearly hysteresis free character with stabilized PCEs of 22.40% and 22.37%, respectively. The inclusion of m‐SnO2 plays a role of an energy bridge, improving electrons collection efficiency, which is supported by photoluminescence and transient photoluminescence characterizations. HTP SnO2 mesoporous PSCs can preserve 97.6% and 80% of their initial PCEs after aging for 25 weeks and 8‐h irradiated/16‐h dark cycle within 104 h. The high stability of HTP SnO2 PSCs may ascribe to low oxygen vacancy and adsorbed water of HTP SnO2. [ABSTRACT FROM AUTHOR]

Abstract: SnO2 has been well investigated in many successful state‐of‐the‐art perovskite solar cells (PSCs) due to its favorable attributes such as high mobility, wide bandgap, and deep conduction band and valence band. Several independent studies show the performances of PSCs with SnO2 are higher than that with TiO2, especially in device stability. In 2015, the first planar PSCs were reported with a power conversion efficiency over 17% using a low temperature sol‐derived SnO2 nanocrystal electron transport layer (ETL). Since then, many other groups have also reported high performance PSCs based on SnO2 ETLs. SnO2 planar PSCs show currently the highest performance in planar configuration devices (21.6%) and are close to the record holder of TiO2 mesoporous PSCs, suggesting their high potential as ETLs in PSCs. The main concerns with the application of SnO2 as ETL are that it suffers from degradation in high temperature processes and that its much lower conduction band compared to perovskite may result in a voltage loss of PSCs. Here, notable achievements to date are outlined, the unique attributes of SnO2 as ETLs in PSCs are described, and the challenges facing the successful development of PSCs and approaches to the problems are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Planar perovskite solar cells (PSCs) based on low‐temperature‐processed (LTP) SnO2 have demonstrated excellent photovoltaic properties duo to the high electron mobility, wide bandgap, and suitable band energy alignment of LTP SnO2. However, planar PSCs or mesoporous (mp) PSCs based on high‐temperature‐processed (HTP) SnO2 show much degraded performance. Here, a new strategy with fully HTP Mg‐doped quantum dot SnO2 as blocking layer (bl) and a quite thin SnO2 nanoparticle as mp layer are developed. The performances of both planar and mp PSCs has been greatly improved. The use of Mg‐SnO2 in planar PSCs yields a high‐stabilized power conversion efficiency (PCE) of close to 17%. The champion of mp cells exhibits hysteresis free and stable performance with a high‐stabilized PCE of 19.12%. The inclusion of thin mp SnO2 in PSCs not only plays a role of an energy bridge, facilitating electrons transfer from perovskite to SnO2 bl, but also enhances the contact area of SnO2 with perovskite absorber. Impedance analysis suggests that the thin mp layer is an “active scaffold” selectively collecting electrons from perovskite and can eliminate hysteresis and effectively suppress recombination. This is an inspiring advance toward high‐performance PSCs with HTP mp SnO2. [ABSTRACT FROM AUTHOR]

Inverted planar perovskite solar cells (PSCs) exhibit advantages in terms of simple device fabrication, good reproducibility, and less hysteresis. However, there still remain challenges to passivate the trap states within the perovskite film and reduce interface instability arising from penetration of moisture and the diffusion of metal electrode. In this work, perovskite passivation is reported using gradiently distributed nonfullerene electron‐rich Lewis bases small molecule IDIC (a π‐conjugated Lewis base: indacenodithiophene end‐capped with 1.1‐dicyanomethylene‐3‐indanone), which is realized through an antisolvent dropping process. Additionally, an inorganic wide band gap Ga2O3 is introduced as a tunneling nanolayer into interface between the metal electrode and electron transport layer that effectively passivate interface and mitigate moisture and metal ion diffusion. These treatments enable the fabrication of CH3NH3PbI3‐based inverted PSCs with excellent power conversion efficiencies up to 19.86% as well as enhanced ambient stability. This work provides new strategies to improve the performance and stability for the inverted PSCs. A perovskite film passivation is reported using gradiently distributed small molecule indacenodithiopheneend‐capped with 1.1‐dicyanomethylene‐3‐indanone. Additionally, inorganic Ga2O3 as a tuneling nanolayer is introduced at electrode interface that effectively passivate interface and mitigate moisture and metal ion diffusion. These treatments enable the fabrication of CH3NH3PbI3‐based inverted perovskite solar cells with excellent power conversion efficiencies up to 19.86% as well as enhanced ambient stability. [ABSTRACT FROM AUTHOR]