Cation-disorder engineering promotes efficient charge-carrier transport in AgBiS2 nanocrystal films

Journal article

Efficient charge-carrier transport is critical to the success of emergent semiconductors in photovoltaic applications. So far, disorder has been considered detrimental for charge-carrier transport, lowering mobilities and causing fast recombination. This work demonstrates that, when properly engineered, cation disorder in a multinary chalcogenide semiconductor can considerably enhance the charge-carrier mobility and extend the charge-carrier lifetime. Here, the properties of AgBiS₂ nanocrystals (NCs) are explored where Ag and Bi cation-ordering can be modified via thermal-annealing. Local Ag-rich and Bi-rich domains formed during hot-injection synthesis are transformed to induce homogeneous disorder (random Ag-Bi distribution). Such cation engineering results in a six-fold increase in the charge-carrier mobility, reaching ∼2.7 cm²V⁻¹s⁻¹ in AgBiS₂ NC thin films. It is further demonstrated that homogeneous cation disorder reduces charge-carrier localisation, a hallmark of charge-carrier transport recently observed in silver-bismuth semiconductors. This work proposes that cation-disorder engineering flattens the disordered electronic landscape, removing tail states that would otherwise exacerbate Anderson localisation of small polaronic states. Together, these findings unravel how cation-disorder engineering in multinary semiconductors can enhance the efficiency of renewable energy applications.

Authors: Righetto, M; Wang, Y; Elmestekawy, KA; Xia, CQ; Johnston, MB

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Advanced Materials
• Volume: 35
• Issue: 48
• Article number: 2305009
• Publication date: 2023-10-24
• Acceptance date: 2023-09-05
• DOI: 10.1002/adma.202305009
• EISSN: 1521-4095
• ISSN: 0935-9648
• Pmid: 37670455
• Language: English
• Keywords: charge-carrier transport; ultrafast localisation; THz spectroscopy; chalcogenides; FFR; cation disorder; photovoltaic materials