Novel Molecular Doping Mechanism for n‐Doping of SnO₂ via Triphenylphosphine Oxide and Its Effect on Perovskite Solar Cells

Abstract

Molecular doping of inorganic semiconductors is a rising topic in the field of organic/inorganic hybrid electronics. However, it is difficult to find dopant molecules which simultaneously exhibit strong reducibility and stability in ambient atmosphere, which are needed for n‐type doping of oxide semiconductors. Herein, successful n‐type doping of SnO2 is demonstrated by a simple, air‐robust, and cost‐effective triphenylphosphine oxide molecule. Strikingly, it is discovered that electrons are transferred from the R3P+O−σ‐bond to the peripheral tin atoms other than the directly interacted ones at the surface. That means those electrons are delocalized. The course is verified by multi‐photophysical characterizations. This doping effect accounts for the enhancement of conductivity and the decline of work function of SnO2, which enlarges the built‐in field from 0.01 to 0.07 eV and decreases the energy barrier from 0.55 to 0.39 eV at the SnO2/perovskite interface enabling an increase in the conversion efficiency of perovskite solar cells from 19.01% to 20.69%.

Secondary Ion Mass Spectrometry (SIMS) for Chemical Characterization of Metal Halide Perovskites

“…[92] ToF-SIMS also demonstrated the successful adoption of an electron donor triphenylphosphine oxide in SnO 2 , which realizes n-type doping of SnO 2 and enhances the conductivity of SnO 2 , enabling the increase of PCE from 19.01% to 20.69%. [93]…”

Modification Engineering in SnO2 Electron Transport Layer toward Perovskite Solar Cells: Efficiency and Stability

“…This strategy has been proved to be effective when applying on optoelectronics and energy devices. [82,83] Tu et al [84] successfully demonstrated an n-type doping of SnO 2 with an air-robust and cheap electron donor triphenylphosphine oxide (TPPO). It has three benzene rings at the three vertices in a plane and an oxygen atom at the other vertex.…”

“…In a recent study from our group, [95] we introduced an inorganic compound, NH 4 Cl, into SnO 2 colloid dispersion and Reproduced with permission. [84] Copyright 2019, John Wiley and Sons. c) Energy band of PSCs, d) Current density versus voltage, and e) J-V curves of PSCs with different ETL.…”

Advances in design engineering and merits of electron transporting layers in perovskite solar cells

“…The most popular inorganic ETLs are transition metal oxides such as TiO 2 , 60 ZnO, 46 and SnO 2 . 61 Although the PSC devices using a TiO 2 ETL have achieved a relatively high efficiency (e.g., above 20%), this metal oxide exhibits some drawbacks such as low electronic conductivity and charge transport. 62,63 Hence, ZnO and SnO 2 , well known for their higher electron mobility (bulk mobility: 205-300 cm 2 V À1 s À1 64 and 240 cm 2 V À1 s À1 , 63 respectively) than that of TiO 2 (bulk mobility: 1 cm 2 V À1 s À1 63 ), have emerged as promising ETLs.…”