Abstract
Auger recombination (AR) can be an important loss mechanism for optoelectronic devices, but it is typically not very efficient at low excitation densities. Here we show that in conductive quantum-dot solids, AR is the dominant charge carrier decay path even at excitation densities as low as 10−3 per quantum dot, and that AR becomes faster as the charge carrier mobility increases. Monte Carlo simulations reveal that this efficient AR results from charge carrier congregation in ‘Auger hot spots’: lower-energy sites that are present because of energy disorder. Disorder-enhanced AR is a general effect that is expected to be active in all disordered materials. The observed efficient AR is an issue of concern for devices that work at charge carrier densities in excess of ~10−3 charge carriers per quantum dot. At the same time, efficient carrier congregation could be exploited for fast optical switching or to achieve optical gain in the near infrared.
Highlights
Auger recombination (AR) can be an important loss mechanism for optoelectronic devices, but it is typically not very efficient at low excitation densities
From Monte Carlo simulations, we find that this efficient AR stems from charge carrier congregation in lowenergy sites that are present because of energy disorder, which we term ‘Auger hot spots’
These carrier densities are high compared with the charge carrier densities in quantum dots (QDs) solar cells and light-emitting diodes (LEDs) under operational conditions
Summary
Auger recombination (AR) can be an important loss mechanism for optoelectronic devices, but it is typically not very efficient at low excitation densities. The observed efficient AR is an issue of concern for devices that work at charge carrier densities in excess of B10 À 3 charge carriers per quantum dot. AR can be an important loss mechanism for many optoelectronic devices, but as it is a higherorder process it is typically not efficient at low excitation densities. We present photoconductivity and transient absorption (TA) studies on QD solids over a wide range of excitation densities and observe higher-order decay at excitation densities as low as 10 À 3 per QD. From Monte Carlo simulations, we find that this efficient AR stems from charge carrier congregation in lowenergy sites that are present because of energy disorder, which we term ‘Auger hot spots’. Fast carrier congregation in low-energy sites could possibly be exploited for fast optical switching or to achieve optical gain in the near infrared (NIR)
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