Highly Photosensitive Colloidal Quantum Well Based Nanocrystal Skins Assisted by Orientation Control

Colloidal quantum wells (CQWs) exhibit superior optical characteristics, including giant oscillator strengths and high absorption cross sections, making them attractive for light-sensing applications. In this study, we fabricated light-sensitive nanocrystal skin (LS-NS) devices using a single-layer edge-up oriented CQW film as the active absorber and achieved a significant enhancement in the performance by leveraging the controlled orientation of the self-assembled CQWs. The LS-NS devices with edge-up oriented CQW film show eight times higher sensitivity and three times higher voltage build-up compared to LS-NS devices with spin-coated CQW films. Such enhancements are due to the trapping of the holes on the edges of the CQWs because of defect-ridden edges, which helps hopping of the holes localized within close proximity to the metal-CQW interface. The LS-NS device with edge-up CQW film exhibited a record-high photovoltage buildup of 600 mV, three times greater than the highest previously reported value for similar LS-NS architectures.