Journal
JOURNAL OF MATERIALS CHEMISTRY A
Volume 7, Issue 38, Pages 21662-21667Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9ta08995k
Keywords
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Funding
- National Natural Science Foundation of China [51703183]
- HKUST President's Office through SSTSP [FP201]
- Basic research and Frontier Exploration of Chongqing Municipal Science and Technology Commission [cstc2018jcyjAX0568]
- Shen Zhen Technology and Innovation Commission [JCYJ20170413173814007, JCYJ20170818113905024]
- Hong Kong Research Grants Council [R6021-18, 16305915, 16322416, 606012, 16303917]
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PEDOT:PSS is widely used in perovskite solar cells (PSCs) as the most popular hole transporting layer (HTL). However, p-i-n type inverted planar PSCs based on the PEDOT:PSS HTL typically exhibit up to 200 mV more voltage loss compared to conventional planar PSCs (n-i-p) that generally show open circuit voltages (V-OC) of around 1.1 V. In this study, we develop a simple, inexpensive and effective interfacial engineering strategy by doping PEDOT:PSS with cesium iodide (CsI) to reduce the voltage loss and achieve highly efficient inverted PSCs. SEM, AFM, and XPS measurements suggest that CsI modifies the interface between PEDOT:PSS and perovskite by reacting with PbI2 to form CsPbI3, thus facilitating interfacial contact and charge transport. Moreover, after CsI-modification (CsI-PEDOT:PSS), the hole transport properties of PEDOT:PSS and the hole extraction are enhanced, while the energy levels are more favorable and charge recombination is suppressed. Importantly, compared to pristine PEDOT:PSS that suffers from a large non-radiative recombination loss (0.375 V), CsI-PEDOT:PSS makes the device to realize an impressively low non-radiative voltage loss (only 0.287 V). As a result, inverted PSCs based on CsI-PEDOT:PSS show a small voltage loss, an excellent power conversion efficiency (PCE) of 20.22%, and no hysteresis and achieve a high V-OC (1.084 V), while the control device without CsI shows an inferior efficiency of 16.57%. Both the high V-OC and PCE are an improvement over literature data on modified PEDOT:PSS-based inverted PSCs.
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