Tailoring organic bulk-heterojunction for charge extraction and spectral absorption in CsPbBr 3 perovskite solar cells
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Published online 30 October 2020 | https://doi.org/10.1007/s40843-020-1499-8
Tailoring organic bulk-heterojunction for charge extraction and spectral absorption in CsPbBr3 perovskite solar cells 1
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Jian Du , Jialong Duan , Yanyan Duan and Qunwei Tang ABSTRACT All-inorganic CsPbBr3 perovskite solar cells (PSCs) are promising candidates to balance the stability and efficiency issues of organic-inorganic hybrid devices. However, the large energy barrier for charge transfer and narrow spectral response are still two challenging problems for performance improvement. We present here an organic bulkheterojunction {poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C61 butyric acid methyl ester (P3HT : PCBM)} photoactive layer to boost the charge extraction and to widen the spectral absorption, achieving an enhanced power conversion efficiency up to 8.94% by optimizing the thickness of P3HT: PCBM photoactive layer, which is much higher than 6.28% for the pristine CsPbBr3 device. The interaction between the carbonyl group in PCBM and unsaturated Pb atom in the perovskite surface can effectively passivate the defects and reduce charge recombination. Furthermore, the coupling effect between PCBM and P3HT widens the spectral response from 540 to 650 nm for an increased short-circuit current density. More importantly, the devices are relatively stable over 75 days upon persistent attack by 70% relative humidity in air condition. These advantages of high efficiency, excellent long-term stability, cost-effectiveness and scalability may promote the commercialization of inorganic PSCs. Keywords: inorganic CsPbBr3 perovskite solar cells, bulk-heterojunction, charge extraction, spectral absorption, stability
INTRODUCTION High power conversion efficiency (PCE) and good longterm stability are two persistent objectives to forward photovoltaic commercialization [1,2]. Organic-inorganic hybrid perovskite solar cells (PSCs) have been a new star in the photovoltaic community in recent years. However, 1 2
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the biggest challenge is to overcome the performance degradation under persistent light, heat and/or moisture attack although the certified efficiency of organic-inorganic hybrid PSC is up to 25.2% [3–6]. The complete substitution of organic species such as + + + + CH3NH3 (MA ) or HC(NH2)2 (FA ) in hybrid per+ ovskites with inorganic Cs to form all-inorganic perovskites demonstrates a great potential to increase the environmental tolerance [7–9]. Among them, all-inorganic CsPbBr3 perovskite with high carrier mobility and stable crystal structure in high-humidity and hightemperature atmospheres is preferred to balance the efficiency and stability for PSC application [10]. Since the birth of the first CsPbBr3 PSC prototype free of holetransporting layer by replacing precious metal electrodes with a cost-effective carbon electrode in 2016 [10,11], the state-of-the-art all-inorganic CsPbBr3 PSCs have achieved the best PCE (>10%) by optimizing the interfacial charge transfer and perovskite film quality [12–14]. However, the PCEs of th
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