Origin of Open-Circuit Voltage Losses in Perovskite Solar Cells Investigated by Surface Photovoltage Measurement

Dabóczi, Mátyás; Hamilton, Iain; Xu, Shiyu; Luke, Joel; Limbu, Saurav; Lee, Jinho; McLachlan, Martyn A.; Lee, Kwang-Hee; Durrant, James R.; Baikie, Iain D.; Kim, Jinhyun

doi:10.1021/acsami.9b16394

Cited by 75 publications

(82 citation statements)

References 54 publications

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“…Photoemission spectroscopy typically generates non-equilibrium conditions with some degree of SPV and band flattening at semiconductor surfaces, on MHP surfaces in particular. [31][32][33] This circumstance places some uncertainty on the equilibrium surface position of E F measured via UPS. To sort out this issue in the present case, we performed KP-CPD/SPV measurements on all the films, in the dark and under controlled white light intensity.…”

Section: Understanding the Origin And Distribution Of Electronic Gap mentioning

confidence: 99%

Gap States in Methylammonium Lead Halides: The Link to Dimethylsulfoxide?

et al. 2020

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Understanding the origin and distribution of electronic gap states in metal halide perovskite (MHP) thin films is crucial to the further improvement of the efficiency and long‐term stability of MHP‐based optoelectronic devices. In this work, the impact of Lewis‐basic additives introduced in the precursor solution on the density of states in the perovskite bandgap is investigated. Ultraviolet photoemission spectroscopy and contact potential difference measurements are conducted on MHP thin films processed from dimethylformamide (DMF)‐based solutions to which either no additive, dimethylsulfoxide (DMSO), or N‐methylpyrrolidine‐2‐thione (NMPT) is added. The results show the presence of a density of states in the gap of methylammonium lead halide films processed from DMSO‐containing solution. The density of gap states is either suppressed when the methylammonium concentration in mixed cation films is reduced or when NMPT is used as an additive, and eliminated when methylammonium (MA) is replaced with cesium or formamidinium (FA). These results are consistent with the notion that reaction products that result from DMSO reacting with MA+ in the precursor solution are responsible for the formation of gap states.

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Section: Understanding the Origin And Distribution Of Electronic Gap mentioning

confidence: 99%

Gap States in Methylammonium Lead Halides: The Link to Dimethylsulfoxide?

et al. 2020

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“…Therefore, the corresponding energy level schematic of the p-i-n planar PSCs is shown in Figure 1h. [29,31] The well-matched energy level between HTL and perovskite layer will reduce the carrier recombination at the interface and simultaneously suppress the energy loss of hole transport, [47,48] contributing to higher V OC and outstanding PSCs performance. [34,49] Then the surface properties of different HTLs are evaluated by measuring the contact angles of dimethyl sulfoxide (DMSO) droplets on PEDOT:PSS, SBS-3-PEDOT:PSS, SBS-9-PEDOT: PSS, and SBS-15-PEDOT:PSS films.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the corresponding energy level schematic of the p‐i‐n planar PSCs is shown in Figure 1h. [ 29,31 ] The well‐matched energy level between HTL and perovskite layer will reduce the carrier recombination at the interface and simultaneously suppress the energy loss of hole transport, [ 47,48 ] contributing to higher V OC and outstanding PSCs performance. [ 34,49 ]…”

Section: Resultsmentioning

confidence: 99%

Sodium Benzenesulfonate Modified Poly (3,4‐Ethylenedioxythiophene):Polystyrene Sulfonate with Improved Wettability and Work Function for Efficient and Stable Perovskite Solar Cells

Wang

et al. 2020

Solar RRL

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The increasing interest in high-performance and economical photovoltaic materials has heightened the emergency to develop the organic-inorganic hybrid halide perovskite solar cells (PSCs). Since the debut of PSCs proposed by Miyasaka et al. in 2009, the PSCs community has achieved great success such as the rocketing power conversion efficiency (PCE) from the initial 3.8% to the latest 25.5% in 2020 in single-junction architectures, and to 29.1% in silicon-based tandem cells. [1-5] This eye-catching breakthrough is contributed by the numerous merits of perovskite material such as long carrier-diffusion length, proper bandgap (1.5-1.6 eV), and facile solution processing. [6-10] In general, the PSCs are classified by architecture into normal (n-i-p) and inverted (p-in) structures, where the perovskite layer is sandwiched between the electron transport layer (ETL) and hole transport layer (HTL). [11,12] For the normal-structured PSCs, metal oxides such as SnO 2 and TiO 2 are commonly used as the bottom ETL, whereas the organic materials such as Spiro-OMeTAD are used as HTL. [13,14] The PSCs feature high efficiency up to 24.82% by introducing fluorinated isomeric analogs in Spiro-OMeTAD. [15] However, the normal-structured PSCs with high PCE are usually based on mesoscopic n-type TiO 2 or insulating Al 2 O 3 to accelerate electron mobility, while the high sintering temperature (>450 C) limits the application in low-cost flexible devices. [16,17] Meanwhile, the upper HTL used organic materials is extremely costly and unstable in air. In contrast, the bottom HTL of inverted (p-in) PSCs is low-temperature processable (<100 C) and cheaper. Therefore, the inverted planar PSCs have a wider application prospect on account of lowtemperature preparation, excellent reproducibility, and negligible hysteresis. [18,19] In addition, the efficiency of the small-area inverted planar PSCs has reached a certified value of 22.3%. [20] Also the record efficiency of over 18% for a mini-module has been achieved in an aperture area of 19.276 cm 2. [21] These results indicate that the inverted structure may be more suitable for manufacturing large-area cells with long-term stability and outstanding efficiency, which means inverted planar PSCs have a better prospect in commercialization. The most common structure of the inverted PSCs is indium tin oxide (ITO)/Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS)/perovskite/PCBM/metal electrode. [22,23] PEDOT:PSS is the most extensively used hole transfer material in inverted PSCs due to its optical transparency, high thermal stability, and good mechanical flexibility.

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“…Hence, every factor involved to influencing the recombination will also have an effect on the V OC . Generally, larger energy gap between perovskite and charge transport layers results in higher V OC loss [ 25 ] and higher recombination rate in these devices.…”

Section: Resultsmentioning

confidence: 99%

Elucidating the Roles of Hole Transport Layers in p‐i‐n Perovskite Solar Cells

Ali

Gao

Zhou

et al. 2020

Adv Elect Materials

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The hole‐transport layer (HTL) is critical to high performance of perovskite solar cells (PSCs) in terms of hole extraction, transportation, and mediation of the following film formation. Here, the interplay between HTLs and open‐circuit voltage (VOC) in PSCs is directly targeted. The results suggest that there is no evident relation between the obtained VOC and the work function of HTLs and it is directly controlled by the recombination losses inside the perovskite material (grain boundaries and trap states) as well as at the interfacial contacts. Additionally, an insight understanding about the charge transfer behavior in PSCs is provided and it is pointed out that the nature of interfacial contacts is a critical factor in defining charge accumulation and recombination at the interfaces. Analysis of the electroluminescence efficiency and transient absorption spectroscopy confirms the better interfacial contact of HTL/perovskite, and larger grain size of perovskite films mediated by the hydrophobic nature of HTLs can collectively and efficiently eliminate nonradiative recombination, resulting in faster charge transfer and lower resistance at the interfaces. This work provides a profound understanding of how the surface hydrophobicity and the interface contact are correlated in terms of nonradiative losses and J–V characters in real devices.

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Origin of Open-Circuit Voltage Losses in Perovskite Solar Cells Investigated by Surface Photovoltage Measurement

Cited by 75 publications

References 54 publications

Gap States in Methylammonium Lead Halides: The Link to Dimethylsulfoxide?

Gap States in Methylammonium Lead Halides: The Link to Dimethylsulfoxide?

Sodium Benzenesulfonate Modified Poly (3,4‐Ethylenedioxythiophene):Polystyrene Sulfonate with Improved Wettability and Work Function for Efficient and Stable Perovskite Solar Cells

Elucidating the Roles of Hole Transport Layers in p‐i‐n Perovskite Solar Cells

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