Abstract
Lead-free double perovskites have recently attracted growing attention as possible alternatives to lead-based halide perovskites in photovoltaics and other optoelectronic applications. The most prominent compound Cs2AgBiBr6, however, presents issues such as a rather large and indirect band gap, high exciton binding energies, and poor charge carrier transport, especially in thin films. In order to address some of these challenges, we systematically modified the stoichiometry of the precursors used for the synthesis of thin films toward a BiBr3-deficient system. In combination with a stoichiometric excess of AgBr, we obtained highly oriented double perovskite thin films. These modifications directly boost the lifetime of the charge carriers up to 500 ns as observed by time-resolved photoluminescence spectroscopy. Moreover, time-resolved microwave conductivity studies revealed an increase of the charge carrier mobility from 3.5 to around similar to 5 cm(2)/(V s). Solar cells comprising the modified films as planar active layers reached power conversion efficiency (PCE) values up to 1.11%, exceeding the stoichiometric reference film (similar to 0.97%), both on average and with champion cells. The results in this work underline the importance of controlling the nanomorphology of the bulk film. We anticipate that control of precursor stoichiometry will also offer a promising approach for enhancing the efficiency of other perovskite photovoltaic absorber materials and thin films.
| Item Type: | Journal article |
|---|---|
| Faculties: | Chemistry and Pharmacy > Department of Chemistry |
| Research Centers: | Center for NanoScience (CENS) |
| Subjects: | 500 Science > 540 Chemistry 500 Science > 500 Science |
| ISSN: | 2574-0962 |
| Language: | English |
| Item ID: | 89859 |
| Date Deposited: | 25. Jan 2022 09:33 |
| Last Modified: | 25. Jan 2022 09:33 |
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