Colloidal Quantum dots (QDs) are heavily researched and now even used in common consumer electronic devices. The nanoscale electronic confinement and surface properties offer a wealth of features that can be exploited for many applications. CsPbI3 is an all-inorganic analog to the hybrid organic cation halide perovskites, but the cubic phase of bulk CsPbI3 (a-CsPbI3)—the variant with desirable band gap—is only stable at high temperatures under conventional constructs. We describe the formation of α-CsPbI3 QD films through a colloidal quantum dot route that are phase-stable for months in ambient air. The films exhibit long-range electronic transport and are used to fabricate colloidal perovskite quantum dot solar cells. The QD solar cells have fascinating performance with an open-circuit voltage of 1.23 volts and power conversion efficiency of 13.4%. Despite very little research on this specific material system to date, the performance surpasses that of any other QD solar cell. This new material system has incredible potential for many applications in optoelectronics, including multijunction photovoltaics, solid-state lighting and display technology. Here, I will present the basics behind the perovskite revolution over the past several years and a look forward into how the QDs offer even more opportunities. We have developed a process whereby the surface of CsPbI3 QDs can be specifically tuned to promote higher conductivity while still retaining quantum confinement. Various ionic species containing a halide are applied as a posttreatment. The specific case of formamidinium iodide is characterized in detail and shows greatly improved mobility within the CsPbI3 QD array while retaining long excited state lifetimes thus showing the ability of QD films to approach optoelectronic figures of merit previously shown in thin films, but with the added benefit of the advantageous QD properties.

Quantum dot perovskite solar cells: Realizing the best of both worlds for revolutionary optoelectronic applications

255th National Meeting (2018)

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