For semitransparent devices with n‐i‐p structures, a metal oxide buffer material is commonly used to protect the organic hole transporting layer from damage due to sputtering of the transparent conducting oxide. Here, a surface treatment approach is addressed for tungsten oxide‐based transparent electrodes through slight modification of the tungsten oxide surface with niobium oxide. Incorporation of this transparent electrode technique to the protective buffer layer significantly recovers the fill factor from 70.4% to 80.3%, approaching fill factor values of conventional opaque devices, which results in power conversion efficiencies over 18% for the semitransparent perovskite solar cells. Application of this approach to a four‐terminal tandem configuration with a silicon bottom cell is demonstrated.
In semitransparent perovskite solar cells with n–i–p configuration, thermal evaporation is the common method to deposit the sputter buffer material, such as molybdenum oxide and tungsten oxide. Buffer layers are especially necessary when using organic hole transporting layers, as they are more susceptible to get damaged when sputtering the top transparent conducting oxide. However, there is a limited selection of possible materials and limited control of the materials properties by thermal evaporation, which leads to inefficient protection against sputtering and poor air stability. While there have been well‐established buffer layers by atomic layer deposition, including tin oxide, for p–i–n structured semitransparent perovskite solar cells, this is not the case for n–i–p structured devices. Here, copper oxide is demonstrated by pulsed‐chemical vapor deposition incorporated into perovskite solar cells for the sputter buffer layer, which result in stable encapsulated semitransparent devices maintaining over 95% of the maximum efficiency under AM 1.5 G at maximum power point tracking for 150 h without any temperature control.
This report addresses indium oxide
doped with titanium and tantulum
with high near-infrared transparency to potentially replace the conventional
indium tin oxide transparent electrode used in semitransparent perovskite
devices and top cells of tandem devices. The high near-infrared transparency
of this electrode is possibly explained by the lower carrier concentration,
suggesting less defect sites that may sacrifice its optical transparency.
Incorporating this transparent electrode into semitransparent perovskite
solar cells for both the top and bottom electrodes improved the device
performance through possible reduction of interfacial defect sites
and modification in energy alignment. With this indium oxide-based
semitransparent perovskite top cell, we also demonstrated four-terminal
perovskite–silicon tandem configurations with improved photocurrent
response in the bottom silicon cell.
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