Constructing binary electron transport layer with cascade energy level alignment for efficient CsPbI2Br solar cells

Chen, Cheng; Wu, Cheng; Ding, Xingdong; Tian, Yi; Zheng, Mengmeng; Cheng, Ming; Xu, Hao; Jin, Zhiwen; Ding, Liming

doi:10.1016/j.nanoen.2020.104604

Cited by 60 publications

(35 citation statements)

References 53 publications

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“…Given the VBM of CsPbI 2 Br (−6.08 eV) is too close to that of the PC 61 BM (−6.0 eV), the TiO 2 interlayer with deeper VBM (−7.85 eV) was introduced, which can effectively block the hole back‐transfer from perovskite to PC 61 BM. [ 17,39 ] In addition, as shown in Figure a,b and Figure S7, Supporting Information, a gradient energy alignment of conduction band minimums (CBMs) between perovskite, TiO 2 , PC 61 BM, and ZnO has formed, [ 15,17,38,39,51 ] which will minimize energy transfer barrier and is beneficial for high open‐circuit voltage ( V OC ) and fill factor (FF). To determine the dynamics of charge transfer and extraction characteristics of different ETLs, steady‐state PL and TRPL spectroscopy were performed.…”

Section: Resultsmentioning

confidence: 99%

“…[ 13,14 ] Nevertheless, the PCEs for CsPbI 2 Br PSCs still lag far behind that of the hybrid PSCs, especially for the inverted structured devices (the latest developments for inverted CsPbI 2 Br PSCs are shown in Table S1, Supporting Information). [ 15 ] Compared with the n–i–p structured device, the development of inverted (p–i–n) structured PSCs is quite attractive and has recently drawn ever‐increasingly research interests [ 16,17 ] because it can not only avoid using the unstable hole transport layers (HTLs), such as Spiro‐OMeTAD (where 4‐ tert ‐butyl pyridine and lithium salts were traditionally adopted as the dopants), but also be more compatible with tandem solar cells. Up to date, most of the perovskite/perovskite tandem solar cells are fabricated with the p–i–n structures.…”

Section: Introductionmentioning

confidence: 99%

“…Cheng et al mediated the electron extraction and transport properties of PC 61 BM via blending it with a newly designed nonfullerene electron transport material SFX‐PDI2 to form a binary ETL, resulting in a PCE of 15.12%. [ 17 ] These results indicated that controlling the energy level and charge transport properties of CTLs is as important as the crystallization tailoring for improving the performance of PSCs.…”

Section: Introductionmentioning

confidence: 99%

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Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

Chen

Tang

et al. 2020

Solar RRL

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The certified laboratory power conversion efficiency (PCE) of 25.2% has recently been achieved for hybrid organic-inorganic lead halide perovskite solar cells (PSCs), [1-5] which is now on par with that of the traditional photovoltaic (PV) devices. Despite their high efficiencies, the intrinsic volatility and thermal instability of organic components in hybrid perovskites are considered to be the important factors that limit their practical applications of PSCs. [6,7] As a potential solution to overcome the shortage of hybrid PSCs, allinorganic perovskites (CsPbX 3 , X ¼ Cl, Br, I, or mixed) have been developed in recent years. [8-10] Among them, mixedhalide inorganic perovskites, CsPbI 2 Br, feature excellent thermal stability and suitable direct bandgap (1.92 eV) for potential usage in tandem solar cells, and have gained increased attentions. [11,12] Much efforts have been dedicated to boost the PCEs of normal structured (n-i-p) CsPbI 2 Br PSCs to over 16% via interfacial engineering, crystallization tailoring, ion substitution, and/or doping of the perovskite. [13,14] Nevertheless, the PCEs for CsPbI 2 Br PSCs still lag far behind that of the hybrid PSCs, especially for the inverted structured devices (the latest developments for inverted CsPbI 2 Br PSCs are shown in Table S1, Supporting Information). [15] Compared with the n-i-p structured device, the development of inverted (p-in) structured PSCs is quite attractive and has recently drawn ever-increasingly research interests [16,17] because it can not only avoid using the unstable hole transport layers (HTLs), such as Spiro-OMeTAD (where 4-tert-butyl pyridine and lithium salts were traditionally adopted as the dopants), but also be more compatible with tandem solar cells. Up to date, most of the perovskite/perovskite tandem solar cells are fabricated with the p-in structures. [18,19] However, the development of inverted wide-bandgap PSCs remains limited. Therefore, it is highly desirable to develop novel strategies for high-efficiency inverted wide-bandgap PSCs. It is well known that the key factors influencing the overall device efficiency should be: 1) the film quality of all functional layers, especially for light absorber and charge transport layers (CTLs); 2) optoelectronic properties of CTLs, such as bandgaps, carrier mobility, and energy levels. [20-23] Therefore, obtaining high-quality perovskite film with reduced defects is the prerequisite for high-performance solar cells. Thus, far ion doping, such as Eu 2þ , [24] Mn 2þ , [25] Nb 5þ , [26] Cu 2þ , [27] Cl À , [25] and Br À , [28] has been proven to be an effective strategy to obtain large grains and in situ strengthen original octahedral structural stability in

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

Chen

Tang

et al. 2020

Solar RRL

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show abstract

“…To date, champion PCEs of 17.03% and 15.92% have been achieved for n–i–p‐type (normal) and p–i–n (inverted)‐type PeSCs, respectively, both based on CsPbI 2 Br. [ 12–18 ] Nevertheless, such PCE values are still lower than those of hybrid PeSCs. Further improvement is highly demanded for all‐inorganic PeSCs.…”

Section: Introductionmentioning

confidence: 94%

Enhancing Built‐In Electric Field and Defect Passivation through Gradient Doping in Inverted CsPbI₂Br Perovskite Solar Cells

et al. 2020

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Organic/inorganic hybrid perovskite solar cells (PeSCs) have been of great interest due to their easy fabrication and high power conversion efficiency (PCE) exceeding 25%. [1-4] Nevertheless, hybrid perovskites (PVKs) suffer from low thermal stability due to the volatile nature of organic cations (i.e., methylamine), [5] which limits the commercial applications of hybrid PeSCs. [6,7] Thus, inorganic cations such as Cs þ are used to replace organic cations, [8] yielding all-inorganic PVKs with considerably improved thermal stability. [9,10] Among various Cs-based inorganic PVKs, dual-halide PVKs of CsPbI 2 Br feature a suitable bandgap (E g) of around 1.9 eV and reasonable phase stability, [11] which make it a promising photoabsorber. To date, champion PCEs of 17.03% and 15.92% have been achieved for n-i-p-type (normal) and p-in (inverted)-type PeSCs, respectively, both based on CsPbI 2 Br. [12-18] Nevertheless, such PCE values are still lower than those of hybrid PeSCs. Further improvement is highly demanded for all-inorganic PeSCs. It has been well recognized that solution-processed inorganic PVK films, especially those prepared at a low temperature, are highly defective, [19] which usually result in large energy loss in PeSCs. For example, the highest reported open-circuit voltages (V OC) are 1.40 and 1.27 V for normal and inverted CsPbI 2 Br PeSCs, [15,16] respectively, both much lower than the E g (%1.9 eV) of PVK. Such large energy loss might be attributed to the severe defect-induced nonradiative recombination. [20,21] In addition, high-density interfacial defects also lead to poor contact between the PVK and electrode, which increases device series resistance and reduces short-circuit current density (J SC) and fill factor (FF). [21] To minimize the bulk and interfacial defects associated with inorganic PVKs, a variety of passivation strategies have been used, [21-28] including additive engineering and post-treatment. Nevertheless, most strategies focus on the passivation of either bulk or interfacial defects rather than both. On the other hand, considerable efforts have been devoted to maximizing the built-in electric field (BEF) of PeSCs, which facilitates carrier separation/transport and hence contributes to the V OC of the device. As the BEF is primarily determined by the work function difference between the two electrodes or transport layers (i.e., electron transport layer [ETL] and hole transport layer [HTL]), [29] BEF enhancement still remains

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“…In the past few years, for achieving this target, quite a few strategies have been proposed, [ 28–37 ] among which, additive engineering has significantly encouraged the improvement of power conversion efficiency (PCE) performance and stability. [ 38,39 ] The reported additives not only gift perovskite films with enhanced crystallinity along with enlarged grain size, but also are advantageous to passivate defect states, thereby lessening the detrimental carrier recombination.…”

Section: Introductionmentioning

confidence: 99%

Efficient Bidentate Molecules Passivation Strategy for High‐Performance and Stable Inorganic CsPbI₂Br Perovskite Solar Cells

Yin

2020

Solar RRL

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Cesium-based all-inorganic perovskites have witnessed extraordinary advances owing to their eye-catching thermal-resistance and photoelectric properties in optoelectronics and photonics application, including solar cells, [1-5] light-emitting diodes, [6,7] photodetectors, [8,9] nanolasers application, [9,10] and so on. In particular, inducing a prominent trade-off between the light absorption and phase stability in comparison with CsPbBr 3 and CsPbI 3 perovskites, [11-13] the mixed-halide inorganic CsPbI 2 Br perovskites with the suitable bandgap have great potential in the application of burgeoning tandem solar cells and semitransparent photovoltaic devices. [14-16] Unfortunately, the serious energy losses (E loss) derived from deleterious nonradiative recombination [17,18] and inimical phase transformation to photo-non-active phase upon exposing to high humidity environment [15,19] are still the primary bottleneck hindering the further commercialization. Consequently, fabricating efficient and stable CsPbI 2 Br perovskite solar cells (PSCs) is a challenging but crucial and meaningful task. It is widely reported that the proliferated dangling bonds at the grain boundaries cause the formation of undesired point defects that result in the carrier recombination and propel the phase transformation to nonfunctional δ phase. [20-22] Moreover, the inimical pinholes caused by poor crystallization make grain boundaries the most susceptible to external erosion, such as moisture and oxygen. [23-25] Thus, considering that the detrimental nonradiative recombination and moisture-driven phase transformation preferentially occur along the weakest grain boundaries region, modulating perovskite crystallization to lower grain boundaries density and passivating defects at the grain boundaries are desirable for fabricating high-quality and stable perovskite films. [26,27] In the past few years, for achieving this target, quite a few strategies have been proposed, [28-37] among which, additive engineering has significantly encouraged the improvement of power conversion efficiency (PCE) performance and stability. [38,39] The reported additives not only gift perovskite films with enhanced crystallinity along with enlarged grain size, but also are advantageous to passivate defect states, thereby lessening the detrimental carrier recombination. Moreover, it is worthwhile mentioning that many additives play a crucial role in the stability improvement. Ma et al. found that guanidinium cations (GA þ) additives in the substitutional sites of perovskite lattice could stabilize the α phase and facilitate a high crystalline CsPbI 2 Br through the relaxation of the lattice strain and the formation of hydrogen bonds, which renders a low fabrication temperature of 140 C. Moreover, GA þ-mediated devices exhibited the superior moisture stability and decreased by only 6% of origin PCE value after 1000 h aging. [31] Wang et al. judiciously incorporated CuBr 2

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Constructing binary electron transport layer with cascade energy level alignment for efficient CsPbI2Br solar cells

Cited by 60 publications

References 53 publications

Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

Enhancing Built‐In Electric Field and Defect Passivation through Gradient Doping in Inverted CsPbI₂Br Perovskite Solar Cells

Efficient Bidentate Molecules Passivation Strategy for High‐Performance and Stable Inorganic CsPbI₂Br Perovskite Solar Cells

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Constructing binary electron transport layer with cascade energy level alignment for efficient CsPbI2Br solar cells

Cited by 60 publications

References 53 publications

Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

Multilayer Cascade Charge Transport Layer for High‐Performance Inverted Mesoscopic All‐Inorganic and Hybrid Wide‐Bandgap Perovskite Solar Cells

Enhancing Built‐In Electric Field and Defect Passivation through Gradient Doping in Inverted CsPbI2Br Perovskite Solar Cells

Efficient Bidentate Molecules Passivation Strategy for High‐Performance and Stable Inorganic CsPbI2Br Perovskite Solar Cells

Contact Info

Product

Resources

About

Enhancing Built‐In Electric Field and Defect Passivation through Gradient Doping in Inverted CsPbI₂Br Perovskite Solar Cells

Efficient Bidentate Molecules Passivation Strategy for High‐Performance and Stable Inorganic CsPbI₂Br Perovskite Solar Cells