Air-Induced High-Quality CH₃NH₃PbI₃ Thin Film for Efficient Planar Heterojunction Perovskite Solar Cells

Abstract

Efficient planar heterojunction perovskite solar cells (PHJ–PSCs) with a structure of ITO/PEDOT:PSS/CH3NH3PbI3/PCBM/Al were fabricated using air-induced high-quality CH3NH3PbI3 perovskite thin films, in which the air-inducing process was controlled with a humidity of ∼40%. The air exposure of CH3NH3PbI3 thin films could dramatically improve their properties with large grains and smooth surface, as well as uniform morphology, resulting in an impressive enhancement in carrier lifetime. The ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy results proved that the CH3NH3PbI3 film was n-doped by the absorption of H2O on the surface but was very stable without obvious degradation for 10 days’ exposure in air. The power conversion efficiency (PCE) of PHJ–PSCs with an air exposure process showed a significant increase up to 16.21% as compared to reference PHJ–PSCs with a PCE of 12.02%. The research work demonstrated that an air-exposure process with a suitable humidity could produce high-quality perovskite thin film for efficient PHJ–PSCs, which may pave a boulevard for fabricating high-efficiency PHJ–PSCs in atmospheric environment.

Low‐Temperature Processed, Efficient, and Highly Reproducible Cesium‐Doped Triple Cation Perovskite Planar Heterojunction Solar Cells

“…Meanwhile, Figure d shows the photovoltage decay lifetime of FA/MA/Cs devices also increases from 6.2 to 8.1 µs, indicating the reduced carrier recombination in ternary FA/MA/Cs photovoltaic devices . The reduction of recombination at the perovskite/interface is beneficial to improve the V oc , which can be attributed to prevent charge accumulation at the perovskite interface …”

“…The grain feature of enhanced uniformity and larger grain size in the FA/MA/Cs film is likely associated with enhanced film reconstruction and mass transport due to the Cs + incorporation, where a promoted crystallization and grain growth occurs. It could be deduced that the perovskite film with larger crystal grains can reduce the number of grain boundaries, which are beneficial to the carrier transport and reduce carrier recombination . The cross‐sectional SEM image with the stack structure of ITO/SnO 2 /perovskite is presented in Figure S2b (Supporting Information), indicating that the thickness of FA/MA/Cs film is about 750 nm and the vertical perovskite is also well‐distributed.…”

“…As shown in Figure a, the time‐resolved PL measurement indicates that the PL lifetime remarkably improves from 19.7 to 27.5 ns with adding Cs into perovskite system. It would result from the reduced crystal defects and less grain boundaries, resulting in suppressed non‐radiative recombination and improved charge transport . Except for the perovskite films, the overall device is a direct mean to detect the film‐dependent photovoltaic properties.…”

Low‐Cost Carbazole‐Based Hole‐Transport Material for Highly Efficient Perovskite Solar Cells

“…[11][12][13] To date, the record PCE of more than 20 %w as achieved using this organic HTM combined with state-of-the-artp erovskite materials as light absorber. [15][16][17][18] Liu et al reporteds piro[fluorene-9,9'-xanthene]-basedH TMs for PSCs, in which not only ah igh PCE but also improved stabilityw ere achieved. Therefore, plenty of effortsw ere made to explore substitutes for this imperfect HTM.…”

“…Therefore, plenty of effortsw ere made to explore substitutes for this imperfect HTM. [15][16][17][18] Liu et al reporteds piro[fluorene-9,9'-xanthene]-basedH TMs for PSCs, in which not only ah igh PCE but also improved stabilityw ere achieved. [19] Xu et al [20] and Bi et al [21] achieved high PCEs of over 19 % using similarly structured small-molecule materials (X59 and X60).…”