Solar energy is the most important energy source on Earth and the natural choice for renewable and environmentally safe energy. In one year the Earth receives 3,850,000 exajoules, orders of magnitude more than the annual global human energy consumption of 550 exajoules in 2010. However, the cost of solar energy is still higher than carbon-based and nuclear energy mainly due to the high cost of crystalline silicon used in commercial solar cells. Therefore, developing higher-efficiency solar cells with lower cost materials is an important requirement for clean and sustainable energy.
The objective of the project was to combine the remarkable optical and electronic properties of two-dimensional (2-D) materials and semiconducting quantum dots (QDs) to obtain higher photovoltaic efficiencies. QDs have excellent light absorption that can be tuned and optimized for sunlight spectrum. In the case of 2-D atomic materials (e.g. graphene, MoS2), they are semi-transparent, with high charge mobility and strong optoelectronic properties. The key idea behind this proposal is combining the advantages of these materials into a hybrid 2-D/QD solar cell to fully exploit the properties of these materials for solar energy photovoltaic harvesting. In this project, we set two specific objectives: 1) Study graphene as a layer to enhance the current collection at the interface between the quantum dots and the metallic electrode, and 2) Develop a novel architecture hybrid solar cells with a Graphene/QuantumDots/Graphene configuration, using QDs as light absorbers and graphene as charge extractor and electric conductor.
Our results concluded that graphene can enhance the current collection since we observed an increase in the short circuit current from 14 mA/cm2 to 18 mA/cm2. The power efficiency increase using graphene is from 4.5% to 5.5%.
