Solution ambient-processed hybrid silicon quantum dots and perovskites solar cells
Vladimir Svrcek1, Calum McDonald1, Conor Rocks1,2, Davide Mariotti2, Takuya Matsui1
1National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
/2Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), Ulster University, BT37 0QB, Northern Ireland, UK, Belfast, United Kingdom

Silicon quantum dots (Si QDs) have HOMO/LUMO level positions dependent on the crystal size and can be well controlled via quantum confinement effects and/or plasma induced surface engineering. Furthermore, such free standing and colloidal Si QDs can be easily used for the design of new hybrid materials through blending, thus enabling band offset and junction engineering in nanoscale hetero-structures. Our studies showed that perovskites could be an attractive matrix material for Si QDs particularly due to their ease of processing, band alignment, long carrier diffusion lengths and low non-radiative recombination rates.  Surfactant-free Si QDs could be easily introduced within two different perovskite matrices and leading to the formation of either a type-I or type-II junction. Here, we present comparative studies on the blending of surfactant-free and surface-engineered Si QDs with the non-toxic lead-free material zero-dimensional methylammonium iodo bismuthate (CH3NH3)3(Bi2I9) (MABI) and the most common methylammonium lead iodide (MAPI) perovskite. We show that both MABI and MAPI perovskite can be well blended with Si QDs and achieve successful coupling of their unique opto-electronic properties. Independently both composites of MABI/Si QDs or MAPI/Si QDs films were incorporated into solar cells and showed improvements in PV performance and stability. We demonstrate that MABI/Si QDs interfaces can be organized into a staggered-gap type-II heterojunction. Whereby in the case of narrow gap (1.5 eV) MAPI perovskite with the wide bandgap of Si QD (2 eV) the position of the HOMO and LUMO levels allows the formation of a novel type-I heterojunction where effective carrier extraction could be demonstrated. The specific implementation of Si QDs with two types of perovskites appears to present synergies that can be tuned to enhance both QD and perovskite key features when applied in a solar cell.

Area: Sub-Area 1.2: Quantum-well, Wire, and Dot-Architectured Devices