Nanocrystal Quantum Dot Photovoltaics

The ability to control structure and composition of materials at the nanoscale has introduced new opportunities to study fundamental light-matter interactions and to apply that understanding towards the development of nanomaterial-enabled optoelectronic devices.  Semiconductor nanostructures in particular have garnered immense interest from fundamental and applied research communities due to the tunable electronic properties (e.g.: energy gap and electron affinity) afforded by precise control over the size, shape, and composition of the nanostructure. Creating materials with programmable electronic structure has potentially major benefits for next-generation of optoelectronic devices, most prominently photovoltaics (PV) and light emitting diodes (LED).  

(a) NQD solar cell device structure (b) surface chemistry treatments and (c) charge generation, recombination, trapping, and extraction

(a) NQD solar cell device structure (b) surface chemistry treatments and (c) charge generation, recombination, trapping, and extraction

Significant recent advances in the fabrication of prototype devices have substantiated the technological potential of semiconductor nanocrystals however, many basic aspects of device performance remain poorly understood.  For example, whether charge collection in a PV cell or injection in a LED is limited by electron or hole transport is largely unknown. Yet optimizing the operation of these devices depends critically on balancing the transfer of both charges. Progress towards realizing the much-heralded technological promise of NCs risks stalling if fundamental knowledge gaps related to the collection or injection of charges into or out of the nanomaterial are not resolved.

Our work, in collaboration with Engstrom and Wise groups pursues use-inspired fundamental studies of charge transport from NCs into other semiconductor materials with two principal goals for the period of the proposed work: (1) to understand and control electronic structure and transport properties across NC interfaces, and (2) to create confined-but-connected nanostructures that balance quantum-confinement and -coupling for optimized light capture and charge transport.

We are excited about opportunities at the confluence of NC solar cells and self-assembly and are intrigued by the prospect of applying recent insights to the discovery of novel ways to: (i) direct the self assembly of nanoscopic building blocks into functional superstructures and (ii) tailor the physiochemical properties of nanostructured surfaces to optimize interfacial charge transport.  Synthetic access to the structures created in the proposed work opens new opportunities to study and resolve important questions concerning the collection or injection of charges in nanostructured semiconductors. Beyond providing new scientific insights, the novel structures introduced here have potentially important implications for new PV and LED technologies.

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