Ligand-Assisted Reconstruction of Colloidal Quantum Dots Decreases Trap State Density

• DOI: 10.1021/acs.nanolett.0c00638
• Publication Date: 2020-03-31T16:55:09Z
• Authors: Bin Sun; Maral Vafaie; Larissa Levina; Mingyang Wei; Yitong Dong; Yajun Gao; Hao Ting Kung; Margherita Biondi; Andrew H. Proppe; Bin Chen; Min-Jae Choi; Laxmi Kishore Sagar; Oleksandr Voznyy; Shana O. Kelley; Frédéric Laquai; Zheng-Hong Lu; Sjoerd Hoogland; F. Pelayo García ...; Edward H. Sargent
• Keywords: Passivation; Trap (plumbing); Surface charge; Potential well

Increasing the power conversion efficiency (PCE) of colloidal quantum dot (CQD) solar cells has relied on improving passivation CQD surfaces, enhancing coupling and charge transport, advancing device architecture. The presence hydroxyl groups nanoparticle surface, as well dimers-fusion between CQDs-has been found to be major source trap states, detrimental optoelectronic properties performance. Here, we introduce a reconstruction step that decreases surface dimers simultaneously. We explored dynamic interaction carriers band-edge states in CQDs using time-resolved spectroscopy, showing ground-state recombination occurs mainly from defects coupled solids passivated simple metal halides. Using reconstruction, demonstrate 60% reduction density 25% improvement diffusion length. These translate into PCE 12.5% compared 10.9% for control CQDs.