The development of semiconductor thin films from nanocrystal ?inks? is emerging as a powerful alternative to conventional methods of film deposition relying on high-vacuum and high-temperature processing of bulk semiconductors. In addition to the anticipated cost reduction, the integration of solution-processed nanocrystal (NC) films into device architectures is inspired by the possibility of tuning the energy of electrical charges in NCs via nanoparticle size. This opens up an additional degree of freedom for manipulating material?s optoelectronic properties and controlling charge flow rates at heterostructured interfaces in solar cells.
The project will develop a general strategy for processing of all-inorganic solar cells from solutions of colloidal semiconductor nanocrystals, using a matrix- encapsulation approach to yield heteroepitaxial nanocrystal/matrix monoliths, expected to show a bulk-like electrical conductance and compelling photovoltaic energy conversion in solution-processed devices. From the fundamental prospective, this work will lay the necessary groundwork needed for incorporating the unique properties of matter at nanoscale into bulk-size materials, potentially leading to the demonstration of new functionalities and properties. From the material fabrication standpoint, this work will advance the current frontiers of nanoparticle self-assembly, thus serving as a benchmark study to aid the on-going research in the area of NC devices.
At present, the appeal of employing semiconductor NC inks for low-temperature (T < 200 °C) fabrication of solar cells is compromised by the instability of surface ligands, which link neighboring nanocrystals in such devices. To address this issue, the project will go beyond the traditional ligand-linking scheme and develop a novel strategy for assembling colloidal semiconductor NCs into all-inorganic solids. To this end, nanocrystals will be bonded into a surrounding matrix of another semiconductor material, designed to preserve optoelectronic properties of individual nanoparticles, while enabling high mobility of electrical charges and excellent thermal/chemical stability of resulting solids. The distance between adjacent NCs in the matrix will determine the degree of inter- nanoparticle electrical coupling and will be used to tune the conductance of the film towards enhancing the charge transport characteristics. Meanwhile, the use of all-inorganic matrices will help suppressing the interaction of NCs with external environment, thus giving rise to improved device stability.
The successful development of inorganic nanocrystal films will result in an alternative, cost-effective architecture of nanocrystal solids, which will reduce the costs and potentially improve the functionality of solid state optoelectronics. This innovation can be harnessed in diverse fields, including solar energy production, photocatalysis, quantum electronics, environmental science, and semiconductor industry. The educational aspects of this interdisciplinary proposal will focus on elucidating students through research activities, mentoring, specialized workshops on nanotechnology, and graduate curriculum development.
