Boosting the performance and stable mesoporous perovskite solar cells by using novel dopant-free quinacridone-based hole transporting materials
Hong Duc Pham a, Sagar Jain M. b, Jinhyun Kim c, Sergei Manzhos d, Krishna Ferron e f, Durrant James R. b c, Sonar Prashant a
a School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), Australia, George Street, 2, Brisbane City, Australia
b SPECIFIC, College of Engineering Swansea University, SPECIFIC, Baglan Bay Innovation Centre, Central Avenue, Baglan, Port Talbot, SA12 7AX, United Kingdom
c Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London, United Kingdom
d Department of Mechanical Engineering, Faculty of Engineering, National University of Singapore, Block EA #07-08, 9 Engineering Drive 1, Singapore 117576
e Centre for Organic Electronics, University of Newcastle, University Drive, Callaghan, NSW 2308
f CSIRO Energy, Newcastle Energy Centre, Australia
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Poster, Hong Duc Pham, 012
Publication date: 23rd October 2018

Up to date, perovskite solar cells (PSCs) have attracted lots of attention from the research community in the world because its power conversion efficiency (PCE) increased quickly from 3.8% to 23.3% within last seven years.[1-2] In spite of achieving the world record PCE rapidly, the commercialization of PSCs still remains challenging due to its high production cost and less stability. The main reason is the intensive use of 2,2’,7,7’-tetrakis(N,N’-di-pmethoxyphenylamino)-9,9’-spirbiuorene (Spiro-OMeTAD) as standard hole transporting material (HTM). Although Spiro-OMeTAD based devices achieved a remarkable performance of 21.1%,[3] there are still some main shortcomings of Spiro-OMeTAD, including high cost and multistep synthesis.[4-5] Extraordinarily, Spiro-OMeTAD requires additives, which enhance the performance of the device, however, at the cost of stability stability.[6-7] These bottlenecks can hamper the progress of low cost and large area flexible PSCs.

Recently, the use of inexpensive organic dyes as hole transporting materials (HTMs)as an alternative to Spiro-OMeTAD for perovskite solar cells (PSCs) has paid attention because it paves way for the development of cost-effective and printable solar cells. Currently, the design of HTMs based on anthanthrone (ANT),[8-9] carbazole (CAZ),[10-12] diketopyrrolopyrrole (DPP),[13-14] and isoindigo (IS)[15] dyes exhibited promising power conversion energy (PCE) in perovskite devices. Among a few dopant-free these dyes-based HTMs, there are several dyes-based HTMs required the additives to enhance the device performance. Though the PCE is enhanced, the presence of these salt dopants leads to the decrease in the stability of the devices and the increase in the cost production. Therefore, the exploration of novel dopant-free organic dyes-based HTMs has been developed.

In this work, we report three novel simple cost efficient solution processable small molecular HTMs based on quinacridone (QA) dye, denoted as ACE-QA-ACE, TPA-QA-TPA, and DPA-QA-DPA. In this design, acenaphthylene (ACE), triphenylamine (TPA) and diphenylamine (DPA) are selected as end-capping groups whereas QA plays a role of the central core. These HTMs were fabricated in mesoscopic TiO2/CH3NH3PbI3/HTM solid-state PSCs without additives. Under 1 sun condition, the devices achieve the maximum efficiency of 17% for ACE-QA-ACE, 6% for TPA-QA-TPA, and 12% for DPA-QA-DPA. First time, we have used QA dye for making such non-doped HTMs for high-performance Perovskite solar cells. Meanwhile, the reference device with doped Spiro-OMeTAD as HTM showed a PCE of 18%. Most importantly, the unencapsulated devices based on these novel pristine HTMs show impressive stability in comparison with the reference devices. These linear symmetrical HTMs pave the way for new classes of the organic hole transporting materials for cost-efficient and large area applications of printed perovskite solar cells.

H.D.P and S.M.J. share equal contribution for this work. H.D.P is thankful to QUT for offering here QUTPRA scholarship to conduct his research work. He is also thankful to Manufacturing with Advanced Materials and the discipline of Molecular Design and Synthesis for funding support of this travel. Author S. M. J. is thankful to Welsh assembly Government funded Sêr Cymru Solar project, EPSRC grants EP/M025020/1 (Supergen Solar Challenge) and Marie-Curie COFUND fellowship for financial support. P.S. is thankful to QUT for financial support and to the Australian Research Council for the Future Fellowship grant FT130101337.

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