Suppressing Charge Extraction Loss in Quantum Dot Infrared Photovoltaics by Optimizing the Charge Transport Layer.

Infrared solar cells (IRSCs), capable of converting low-energy infrared photons to electron-hole pairs, are promising infrared optoelectronic devices because of their extended utilization region of the solar to short-wavelength infrared region. For PbS QDs IRSCs, charge extraction loss, easily generated at the interfaces, has been one of the dominate obstacles impeding the improvement of device efficiencies due to too many trap states and mismatched energy levels between the photoactive layer and electron transport layer (ETL). Herein, an advanced ZnO ETL was developed to improve the extraction of photogenerated charges from the PbS QD photoactive layer to ETLs. The advanced ETL film exhibited effectively suppressed trap states and better-matched energy levels compared with the QD layer. As a consequence, high-performance PbS QD IRSCs with the highest infrared power conversion efficiencies of 1.26% under 1100 nm filtered solar illumination are achieved, suggesting an effective and facile route for enhancing the charge extraction in infrared photovoltaics.