Operando-photoluminescence spectroscopy for accessing radiative and non-radiative losses in perovskite solar cells
Weidong Xu a, Lucy Jessica Fiona Hart a, Benjamin Moss a, Thomas J. Macdonald a, Richard Pacalaj a, Pietro Caprioglio b, Robert DJ Oliver b, James R Durrant a
a Centre for Processable Electronics, Department of Chemistry, Imperial College London W12 0BZ, U.K.
b Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, U.K.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Weidong Xu, presentation 028
DOI: https://doi.org/10.29363/nanoge.hopv.2022.028
Publication date: 20th April 2022

Organic-inorganic metal halide perovskite solar cells (PSCs) have demonstrated great potential to become the next generation solar energy harvesters. Whilst few of the n-i-p structured PSCs have reached over 25% efficiency,[1,2] most of the p-i-n based ones still lag behind due to sever non-radiative losses either/both in the bulk or/and at the perovskite/charge transport layer interface. Therefore understanding the mechanism of these non-radiative recombination processes is a key to further improve the device performance towards Shockley-Queisser (S-Q) limit.

Photoluminescence (PL) spectroscopy is one of the most widely used research techniques to access radiative recombination so as to interpret non-radiative recombination. Recently, this method has shown its success in PSC by calculating the quasi-fermi-level-splitting (QFLS) inside the bulk perovskite through the emitted photons.[3,4] Whilst most of the examples were conducted at open-circuit condition for estimating the VOC losses, the device performance of a PSC is determined by the current-voltage (J-V) scan within the range of 0V to VOC. In order to explore the full loss mechanism of a device under operating, we have built a system to acquire both the operando PL spectrum and the output current of a PSC at each voltage point during a J-V scan. This allows us to get both a PL-V curve showing the bulk information and a J-V curve showing the out-circuit information from a single measurement.

By studying the p-i-n PSCs with different electron transport layers (ETL), our results suggest that strong surface recombination at the perovskite/ETL interface will induce a mismatch between QFLS and qV, resulting in a discrepancy between PL-V and J-V curve in the shape. We’ve also observed all PSCs show large QFLS at short-circuit conditions, demonstrating charge accumulation in the bulk perovskite is a general trend. We suggest that this trend is not only related to the interfacial energetics, but also to the ion migration caused field screening in the bulk, which has been further proved by numerical simulations based on Driftfusion model. [5]

This project is funded by the Application Targeted and Integrated Photovoltaics (ATIP) project (EP/T028513/1) and the SUNRISE project (EP/T032591/1). W.X. gratefully acknowledges the Imperial- China Scholarship Council scholarship.

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