Abstract
AbstractThere has been a meteoric rise in the commercial potential of lead halide perovskite optoelectronic devices since photovoltaic cells and light‐emitting diodes based on these materials were first demonstrated. One key challenge common to each of these optoelectronic devices is the need to suppress nonradiative recombination, a process that limits the maximum achievable efficiency in photovoltaic cells and light‐emitting diodes. In this Progress Report, recent studies that seek to minimize this loss pathway in perovskites through a photobrightening treatment, whereby the luminescence efficiency is enhanced through a light illumination passivation process are examined. The sensitivity of this effect to various experimental considerations is examined, including atmosphere, photon energy, photon dose, and also the role of perovskite composition and morphology; under certain conditions there can even be photodarkening effects. Consideration of these factors is critical to resolve seemingly conflicting literature reports. Proposed mechanisms are scrutinized, revealing that there is now some consensus but further work is needed to identify the specific defects being passivated and elucidate universal mechanisms. Finally, the prospects for these treatments to minimize halide migration and push the properties of polycrystalline films towards those of their single‐crystal counterparts are discussed.
Highlights
Over the past decade, hybrid perovskites have re-energised interest in high-performance, lowcost devices for energy harvesting and light emission thanks to their remarkably clean semiconductor properties and solution processability.[1]
Facile composition engineering enables the development of perovskite solar cells (PSCs) with band gaps tuned for maximum power conversion efficiency (PCE) in both single junction and tandem solar cell configurations,[2,3,4] and perovskite light emitting diodes (PeLEDs) that can be designed to emit at energies across the visible and near-IR regions of the electromagnetic spectrum.[5]
A combination of all of the above may be required to achieve the maximum luminescence yields and film stabilities. In this Progress Report, we scrutinised the literature on photobrightening and photodarkening processes in lead halide perovskites, where photobrightening refers to the enhancement in luminescence efficiency through continued light illumination
Summary
Hybrid perovskites have re-energised interest in high-performance, lowcost devices for energy harvesting and light emission thanks to their remarkably clean semiconductor properties and solution processability.[1]. As reported by our group and others, this process, hereafter referred to as photobrightening, can substantially enhance luminescence yields of polycrystalline thin films,[35] reaching extremely low trap densities with corresponding improvements in PSC performance Atmospheric molecules such as oxygen and water (and their derivatives) are known to degrade perovskite films over extended exposure periods.[33,36,37] the question over the universality of the effect with different systems and conditions and long-term stability issues could limit the commercial viability of this treatment. This work presents a framework that will direct future research on defect passivation approaches and our fundamental understanding of carrier recombination in perovskites
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