Dr. Jafar I. Khan Profile

Dr. Jafar I. Khan

Research Scientist at King Abdullah Univ of Science and Technology

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Publications (3)

SPIE Journal Paper | 23 August 2022 Open Access

P3HT:PCBM polymer solar cells from a didactic perspective

Shahidul Alam, Aman Anand, Md Moidul Islam, Rico Meitzner, Aurelien Sokeng Djoumessi, Josef Slowik, Zekarias Teklu, Peter Fischer, Christian Kästner, Jafar Khan, Ulrich Schubert, Frédéric Laquai, Harald Hoppe

JPE, Vol. 12, Issue 03, 035501, (August 2022) https://doi.org/10.1117/12.10.1117/1.JPE.12.035501

KEYWORDS: Solar cells, Annealing, Picosecond phenomena, Polymers, Electrodes, Crystals, Resistance, Electroluminescence, Aluminum, Thin films

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Proceedings Article | 10 March 2020 Presentation

Probing carrier extraction from lead halide perovskite to charge transport layers by ultrafast spectroscopy (Conference Presentation)

Jafar Khan, Esma Ugur, Furkan Isikgor, Erkan Aydin, Mindaugas Kirkus, Marios Neophytou, Stefaan De Wolf, Iain McCulloch, Frederic Laquai

Proceedings Volume 11278, 112781J (2020) https://doi.org/10.1117/12.2544566

KEYWORDS: Perovskite, Lead, Ultrafast laser spectroscopy, Solar cells, Interfaces, Luminescence, Polymers, Photovoltaics, Metals, Ultrafast measurement systems

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Solution-processed metal-halide perovskite solar cells (PSCs) have received immense attention in the field of photovoltaic research due to their outstanding power conversion efficiency (PCE), which has surpassed 24% in a relative short time. Understanding carrier losses at metal halide perovskite/charge transport layer interfaces is a pre-requisite to bring the efficiency closer to the Shockley-Queisser limit. Ultrafast transient absorption spectroscopy is a vital tool to study such a processes and specifically interfacial recombination can accessed through these measurements, and further in-sights into losses associated with the open circuit voltage Voc are gained. Transient spectroscopy techniques will be used to unravel the dynamics of processes limiting the photoluminescence quantum efficiency and thus the Voc. Employing both transient photoluminescence and transient absorption techniques, enables differentiation be-tween various recombination processes. Here we study the impact of the different hole transport layers, namely, PDPP-3T, NiO and PTAA hole transport layers and reveal the charge carrier recombination. We report the direct observation of hole extraction and carrier recombination dynamics of mixed-cation lead mixed-halide perovskite layers interfacing with a polymeric hole transport layer: PDPP-3T. The dynamics of the ground state bleach of the polymer, which directly reveals the hole extraction and re-combination at the perovskite/polymer interface. The perovskite hole mobility was found to be 3.08 cm2 V-1 s-1. To gain further insight into the hole extraction dynamics, we vary the thickness of the perovskite film. We observe that the hole extraction time is slower with increasing the perovskite thickness following optical excitation from the perovskite side. Mimicking the device architecture via introducing an electron transport layer to the perovskite/PDPP-3T stack resulted in slower carrier recombination dynamics due to decreased charge carrier recombination in the perovskite.

Proceedings Article | 10 March 2020 Presentation

Impact of PL reabsorption and surface passivation on the internal quantum efficiency of perovskite solar cells (Conference Presentation)

Mingcong Wang, Kai Wang, Yajun Gao, Jafar Khan, Dalia Al Nakdali, Erkki Alarousu, Stefaan De Wolf, Denis Andrienko, Frederic Laquai

Proceedings Volume 11275, 112750E (2020) https://doi.org/10.1117/12.2544139

KEYWORDS: Solar cells, Internal quantum efficiency, Perovskite, Luminescence, Terahertz spectroscopy, Quantum efficiency, Time resolved spectroscopy, Spectroscopy, Diffusion, Probability theory

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