Optimizing Composition and Morphology for Large-Grain Perovskite Solar Cells via Chemical Control

Tsai, Hsinhan; Nie, Wanyi; Cheruku, Pradeep; Mack, Nathan H.; Xu, Pengwu; Gupta, Gautam; Mohite, Aditya; Wang, Hsing‐Lin

doi:10.1021/acs.chemmater.5b02378

Cited by 82 publications

(82 citation statements)

References 40 publications

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“…Interestingly, in the 400 to 500 nm range, the absorption intensity gradient was increased when the doping concentration was below 9 mg/mL, mainly attributed to the formation of spiro-OMeTAD + . According to Figure 3a, it was vital to achieve the optimum doping concentration of iodine in the layer of spiro-OMeTAD, because iodine has a strong oxidation effect [27] on both perovskite and hole transport material. According to experimental details, the mole concentration of spiro-OMeTAD was approximately 6.452 × 10 −2 mmol/mL.…”

Section: Resultsmentioning

confidence: 99%

Effects of Iodine Doping on Carrier Behavior at the Interface of Perovskite Crystals: Efficiency and Stability

et al. 2018

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Abstract:The interface related to the polycrystalline hybrid perovskite thin film plays an essential role in the resulting device performance. Iodine was employed as an additive to modify the interface between perovskite and spiro-OMeTAD hole transport layer. The oxidation ability of iodine significantly improved the efficiency of charge extraction for perovskite solar cells. It reveals that the Open Circuit Voltage (V oc ) and Fill Factor (FF) of perovskite solar cells were improved substantially due to the dopant, which is mainly attributed to the interfacial improvement. It was found that the best efficiency of the devices was achieved when the dopant of iodine was in equivalent mole concentration with that of spiro-OMeTAD. Moreover, the long-term stability of the corresponding device was investigated.

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Section: Resultsmentioning

confidence: 99%

Effects of Iodine Doping on Carrier Behavior at the Interface of Perovskite Crystals: Efficiency and Stability

et al. 2018

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“…wavelength absorption. [50] This is beyond the scope of the current work and is being investigated separately. Now, taking into account the PLQE of these materials at 1 sun intensity (0.0007 ± 10 −5 and 0.009 ± 10 −4 for 60% and 80% Sn content thin films, respectively) the V OC loss was estimated, using kTln (PLQE), [51][52][53] to be ≈200 and 120 meV, respectively for 60% and 80% Sn content based PVs.…”

Section: Doi: 101002/adma201604744mentioning

confidence: 95%

“…[35,48,49] The EQEs measured for these devices are lower at higher wavelengths due to lower absorption in the IR absorption compared to that in the visible region (see the Supporting Information, Figure S1) and this could potentially limit the J SC 's that we get in our devices. This problem has been attributed to the presence of MAPb x Sn 1-x Cl 3 up to 33% of the total material in the thin film that does not absorb visible light due to its large bandgap (>3 eV), [50] and the longer wavelength absorption and EQE can be increased by adding molecular iodine into the precursor solution that reduces this pure chloride perovskite phase to below 10%, hence, enhancing the longer Adv. Mater.…”

Section: Doi: 101002/adma201604744mentioning

confidence: 99%

High Open‐Circuit Voltages in Tin‐Rich Low‐Bandgap Perovskite‐Based Planar Heterojunction Photovoltaics

et al. 2016

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] Of relevance to this work is the binary metal perovskite CH 3 NH 3 (Pb x Sn 1-x )I 3 [0 ≤ x ≤ 1]. [30,31] Interestingly, the bandgap bows and becomes lower when Sn 2+ is substituted by Pb 2+ for samples with 80% and 60% Sn content compared to 100% Sn-based perovskite, in line with previous observations. [30,31] While such tin-based perovskites offer tunable bandgaps down to 1.1 eV, the fabrication of efficient optoelectronic devices has been impeded by factors including poor semiconductor quality and low surface coverage. [30] As a consequence, solar cells made using these perovskites often exhibit very low efficiencies, with typical PCEs < 1% obtained for planar heterojunction devices. [30] To overcome this challenge, we have developed a novel elevated temperature processing method (depicted in Figure 1A), [32] for preparing CH 3 NH 3 (Pb x Sn 1-x )I 3 perovskites on a Poly(3,4-ethylenedioxythiophene):poly(styrenesulf onate) (PEDOT:PSS)/nickel oxide (NiO) bilayer, which results in the formation of large micron-sized grains ( Figure 1B) with almost complete substrate coverage. Our semiconductors not only exhibit relatively low energetic and structural disorder but also impart high PCEs when fabricated into a PV device. For PVs prepared using the lowest bandgap perovskites, open circuit voltages (V OC 's) approaching the prediction of the Shockley-Queisser (S-Q) model are demonstrated. Such promising performance metrics are obtained against a backdrop of fast radiative recombination and low photoluminescence quantum efficiencies (PLQEs), pointing toward the crucial role of high intrinsic charge carrier mobility in these low-bandgap semiconductors.To study the optical properties of the CH 3 NH 3 (Pb x Sn 1-x )I 3 [0 ≤ x ≤ 1] perovskite thin films, linear absorption and photoluminescence (PL) were measured as shown in Figure S1 (Supporting Information). It can be observed in Figure 1C that the bandgap bows as we substitute Pb 2+ in place of Sn 2+ (until 40% Sn 2+ ions are replaced by Pb 2+ ) and results in a nonmonotonic bandgap lowering similar to what was observed previously by Hao etal. [31] Briefly, the bandgap of the 60% and 80% Sn content films exhibit a lower bandgap than the 100% Sn-substituted films. A similar trend can also be traced in the PL spectra (see Figure S1B of the Supporting Information) where the PL spectra of 80% and 60% Sn content thin-film samples are red-shifted compared to the 100% Sn content thinfilm sample, which is consistent with the absorption spectra. Such anomalous bandgap bowing and lack of conformity with Vegard's law [31,33] have been attributed to the competition The performance of organometallic halide (hybrid) perovskite solar cells has improved dramatically in just a few years, with photovoltaic (PV) power conversion efficiencies (PCEs) now exceeding 22% for state-of-the-art devices. [1][2][3][4][5] This remarkable result, coupled with their low cost, tunability, and versatile lowtemperature preparation methods, makes hybrid perovskites one of the most promising semiconduct...

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“…After confirming the purity of the n = 5 powders, thin films were grown using the previously described hot-casting www.advenergymat.de www.advancedsciencenews.com method [4,7,25,42] (see the Experimental Section for more details). We find that 2D perovskite materials of the same chemical formula (BA 2 MA n-1 Pb n I 3n+1 ) processed under identical conditions (0.225 m in DMF, hot-cast at 110 °C) yield similar morphologies, [25] while the degree of film crystallinity appears to be of inherent nature and is highly sensitive to the [(MA) n−1 Pb n I 3n+1 ] 2− inorganic layer thickness.…”

Section: Impact Of Solvent On Film Microstructure and Morphologymentioning

confidence: 99%

Understanding Film Formation Morphology and Orientation in High Member 2D Ruddlesden–Popper Perovskites for High‐Efficiency Solar Cells

Soe

Nie

Stoumpos

et al. 2017

Advanced Energy Materials

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International audience2D Ruddlesden–Popper (RP) perovskites have recently emerged as promising candidates for hybrid perovskite photovoltaic cells, realizing power-conversion efficiencies (PCEs) of over 10% with technologically relevant stability. To achieve solar cell performance comparable to the state-of-the-art 3D perovskite cells, it is highly desirable to increase the conductivity and lower the optical bandgap for enhanced near-IR region absorption by increasing the perovskite slab thickness. Here, the use of the 2D higher member (n = 5) RP perovskite (n-butyl-NH3)2(MeNH3)4Pb5I16 in depositing highly oriented thin films from dimethylformamide/dimethylsulfoxide mixtures using the hot-casting method is reported. In addition, they exhibit superior environmental stability over thin films of their 3D counterpart. These films are assembled into high-efficiency solar cells with an open-circuit voltage of ≈1 V and PCE of up to 10%. This is achieved by fine-tuning the solvent ratio, crystal growth orientation, and grain size in the thin films. The enhanced performance of the optimized devices is ascribed to the growth of micrometer-sized grains as opposed to more typically obtained nanometer grain size and highly crystalline, densely packed microstructures with the majority of the inorganic slabs preferentially aligned out of plane to the substrate, as confirmed by X-ray diffraction and grazing-incidence wide-angle X-ray scattering mapping

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Optimizing Composition and Morphology for Large-Grain Perovskite Solar Cells via Chemical Control

Cited by 82 publications

References 40 publications

Effects of Iodine Doping on Carrier Behavior at the Interface of Perovskite Crystals: Efficiency and Stability

Effects of Iodine Doping on Carrier Behavior at the Interface of Perovskite Crystals: Efficiency and Stability

High Open‐Circuit Voltages in Tin‐Rich Low‐Bandgap Perovskite‐Based Planar Heterojunction Photovoltaics

Understanding Film Formation Morphology and Orientation in High Member 2D Ruddlesden–Popper Perovskites for High‐Efficiency Solar Cells

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