Publication date: 7th February 2022
Thanks to their high absorption coefficient and ideal band-gap [1], perovskite materials are good candidates for the next generation of solar cells with an impressive power conversion efficiency of 25.5 % certified [2]. However, the development of perovskite based solar cells is impeded by obstacles including degradation of the perovskite layer by oxygen and moisture under illumination. Photoluminescence is a measure of photoexcited carrier radiative recombinations and is thus a great tool for studying charge carrier processes in solar cells as the later operates through the absorption of light. Especially, time-resolved PL (TRPL) allows to study transient phenomenon such as carrier recombination and injection. However, the measurement and interpretation TRPL of perovskites is usually complicated due to the complex recombination processes happening in these materials. We present here the PEARS (PErovskite cArrier Recombination Simulator) web tool for easily fitting experimental TRPL decays of perovskite materials. This free-to-use tool allows to fit TRPL decays using two model previously used in the literature [3]: the bimolecular-trapping and bimolecular-trapping-detrapping models. Both models consider the direct bimolecular recombination of electron and holes but differ in their treatment of non-radiative recombinations through trap states. The bimolecular-trapping-detrapping model considers the filling and emptying of trap states through trapping and detrapping respectively, while the bimolecular-trapping model assumes that the detrapping is fast enough such that the trap states remain mostly empty. Including the input data, the user only needs to provide the initial carrier concentration calculated from the excitation fluence used. If parameter values (e.g., doping concentration) are known, the user can fix them or set guess values otherwise. The web tool provides an analysis of the fitting by calculating the different process contributions and potential carrier accumulation due to incomplete carrier recombination between excitation pulses if the excitation repetition period is provided.
We are grateful for the financial support of the EPSRC (EP/R016666/1 and EP/S001336/1) and both the EPSRC and Innovate UK for the SPECIFIC Innovation and Knowledge Centre and the European Regional Development Fund through the Welsh Government for support to the Sêr Solar program. MLD is grateful for funding through the EPSRC GCRF SUNRISE project (EP/P032591/1). We would like to acknowledge the assistance provided by the European Regional Development Fund through the Welsh Government (80708), the Ser Solar project via Welsh Government and Edinburgh Instruments.