Microsecond Carrier Lifetimes, Controlled p-Doping, and Enhanced Air Stability in Low-Bandgap Metal Halide Perovskites.

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Bowman, Alan R 
Klug, Matthew T 
Doherty, Tiarnan AS 
Farrar, Michael D 
Senanayak, Satyaprasad P 

Mixed lead-tin halide perovskites have sufficiently low bandgaps (∼1.2 eV) to be promising absorbers for perovskite-perovskite tandem solar cells. Previous reports on lead-tin perovskites have typically shown poor optoelectronic properties compared to neat lead counterparts: short photoluminescence lifetimes (<100 ns) and low photoluminescence quantum efficiencies (<1%). Here, we obtain films with carrier lifetimes exceeding 1 μs and, through addition of small quantities of zinc iodide to the precursor solutions, photoluminescence quantum efficiencies under solar illumination intensities of 2.5%. The zinc additives also substantially enhance the film stability in air, and we use cross-sectional chemical mapping to show that this enhanced stability is because of a reduction in tin-rich clusters. By fabricating field-effect transistors, we observe that the introduction of zinc results in controlled p-doping. Finally, we show that zinc additives also enhance power conversion efficiencies and the stability of solar cells. Our results demonstrate substantially improved low-bandgap perovskites for solar cells and versatile electronic applications.

3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 3406 Physical Chemistry, 40 Engineering, 4016 Materials Engineering
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ACS Energy Lett
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American Chemical Society (ACS)
Royal Society (UF150033)
European Research Council (756962)
Engineering and Physical Sciences Research Council (EP/M005143/1)
Engineering and Physical Sciences Research Council (EP/R023980/1)
EPSRC (1948703)
EPSRC (EP/M005143/1 and DTP funding) Royal Society ERC