HYBRID QUANTUM-DOT/TWO-DIMENSIONAL MATERIALS PHOTOVOLTAIC CELLS

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The development of high-efficiency and low-cost solar cells is one of the most crucial challenges to secure a clean and sustainable energy source. The novel and tunable optoelectronic properties of nanomaterials are a very promising but still challenging route to achieve this goal. In this project, we propose to combine the advantages of two important nanoscale materials, semiconductor quantum dots (QD) and two-dimensional atomic layered (2-D) materials, to realize high-efficiency hybrid solar cells. Quantum dots are one of the best absorbing and carrier photogenerators due to multiple exciton generation and their size-tunable and direct band gap, however, their poor dot-to-dot conductivity has been a major limitation for photovoltaic devices. We propose to overcome this limitation by intercalating 2-D materials that have shown high charge mobility and strong optoelectronic properties. We propose a tandem configuration based on a stack of QD layers for strong carrier photogeneration, with intercalated 2-D atomic layers for efficient charge and photocurrent extraction. We will study the charge transfer and separation at the interface of QDs and 2-D layers, both of which are strongly affected by quantum confinement. The co-supervisors of this project, Prof. Konstantatos and Prof. Koppens at ICFO, have demonstrated a QD/2-D(graphene) phototransistor with a photoresponse up to 5 orders of magnitude higher than phototransistors based on single graphene or MoS2 atomic layers without QDs, showing the potential of QD/2-D hybrid devices for photovoltaics. In addition to QDs, we will also use small band gap materials, such as phosphorene and other 2-D semiconductors that can harvest energy from infrared hot sources in dark conditions. The proposed hybrid QD/2-D solar cell architecture can have a strong technological impact since both materials can be produced in large scale by chemical synthesis and surpass the performance of current photovoltaic technologies.