Light absorption and recycling in hybrid metal halide perovskites photovoltaic devices
Advanced Energy Materials Wiley 10:10 (2020) 1903653
Abstract:
The production of highly efficient single‐ and multijunction metal halide perovskite (MHP) solar cells requires careful optimization of the optical and electrical properties of these devices. Here, precise control of CH3NH3PbI3 perovskite layers is demonstrated in solar cell devices through the use of dual source coevaporation. Light absorption and device performance are tracked for incorporated MHP films ranging from ≈67 nm to ≈1.4 µm thickness and transfer‐matrix optical modeling is utilized to quantify optical losses that arise from interference effects. Based on these results, a device with 19.2% steady‐state power conversion efficiency is achieved through incorporation of a perovskite film with near‐optimum predicted thickness (≈709 nm). Significantly, a clear signature of photon reabsorption is observed in perovskite films that have the same thickness (≈709 nm) as in the optimized device. Despite the positive effect of photon recycling associated with photon reabsorption, devices with thicker (>750 nm) MHP layers exhibit poor performance owing to competing nonradiative charge recombination in a “dead‐volume” of MHP. Overall, these findings demonstrate the need for fine control over MHP thickness to achieve the highest efficiency cells, and accurate consideration of photon reabsorption, optical interference, and charge transport properties.Time-resolved THz spectroscopy of metal-halide perovskite single crystals and polycrystalline thin films
Institute of Electrical and Electronics Engineers (IEEE) 00 (2019) 1-2
Structural and Optical Properties of Cs2AgBiBr6 Double Perovskite
ACS Energy Letters American Chemical Society (ACS) (2018) 299-305
Electronic Traps and Phase Segregation in Lead Mixed-Halide Perovskite
ACS Energy Letters (2018) 75-84
Abstract:
© 2018 American Chemical Society. An understanding of the factors driving halide segregation in lead mixed-halide perovskites is required for their implementation in tandem solar cells with existing silicon technology. Here we report that the halide segregation dynamics observed in the photoluminescence from CH3NH3Pb(Br0.5I0.5)3 is strongly influenced by the atmospheric environment, and that encapsulation of films with a layer of poly(methyl methacrylate) allows for halide segregation dynamics to be fully reversible and repeatable. We further establish an empirical model directly linking the amount of halide segregation observed in the photoluminescence to the fraction of charge carriers recombining through trap-mediated channels, and the photon flux absorbed. From such quantitative analysis we show that under pulsed illumination, the frequency of the modulation alone has no influence on the segregation dynamics. Additionally, we extrapolate that working CH3NH3Pb(Br0.5I0.5)3 perovskite cells would require a reduction of the trap-related charge carrier recombination rate to ≲105s-1 in order for halide segregation to be sufficiently suppressed.Bimolecular recombination in methylammonium lead triiodide perovskite is an inverse absorption process.
Nature communications 9:1 (2018) 293-293