The efficiencies of perovskite solar cells, PSCs, are now reaching such consistently high levels that scalable manufacturing at low cost is becoming critical. However, this remains challenging due to the expensive hole-transporting materials usually employed, and difficulties associated with the scalable deposition of other functional layers.

By simplifying the device architecture, hole-transport-layer-free PSCs with improved photovoltaic performance were fabricated by researchers in the Huang Group via a scalable doctor-blading process. Molecular doping of halide perovskite films improved the conductivity of the films and their electronic contact with the conductive substrate, resulting in a reduced series resistance. It facilitates the extraction of photoexcited holes from perovskite directly to the conductive substrate. The bladed hole-transport-layer-free PSCs showed a stabilized power conversion efficiency above 20.0%.

An additive-assisted strategy for p-type molecular doping of solution-bladed perovskite films was demonstrated. This effective doping strategy eliminates the HTL preparation step, thus simplifying the PSC fabrication process and reducing costs. Extending the application of this doping technique to a broader range of semiconducting materials will definitely benefit the construction of other high performance, printed optoelectronic devices. This work represents a significant step towards the scalable, cost-effective manufacturing of PSCs with both high performance and simple fabrication processes.