Organometallic Halide Perovskites: Sharp Optical Absorption Edge and Its Relation to Photovoltaic Performance

Wolf, Stefaan De; Holovský, Jakub; Moon, Soo‐Jin; Löper, P.; Niesen, Bjoern; Ledinský, Martin; Haug, Franz‐Josef; Yum, Jun‐Ho; Ballif, Christophe

doi:10.1021/jz500279b

Cited by 2,242 publications

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References 44 publications

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“…6b 32,33 . The extent of the absorption tail below the band gap is correlated with the degree of electronic disorder within the material, which could originate from thermal fluctuation of the ions composing the material but also from defects of the crystalline structure.…”

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confidence: 99%

Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells

et al. 2015

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To date, there have been a plethora of reports on different means to fabricate organicinorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.

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Section: Resultsmentioning

confidence: 99%

Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells

et al. 2015

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“…[ 20,21 ] Furthermore, low Urbach energies, which are extracted from near band edge optical absorption measurements and serve as a benchmark for crystalline phase disorder, indicate low disorder and sharp band edges for lead tri-halide perovskites (15-23 meV). [ 22,23 ] All of these properties contribute to high open-circuit voltages, long charge-carrier lifetimes, and micrometer diffusion lengths, which are crucial for planar-hetero junction photovoltaics. [ 1,24 ] Nonetheless, these parameters are also expected to depend on the infl uence of crystallization condition on perovskite morphology in fabricated fi lms.…”

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Charge‐Carrier Dynamics and Mobilities in Formamidinium Lead Mixed‐Halide Perovskites

et al. 2015

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by at least four orders of magnitude. [ 17,18 ] MAPbI 3 also appears to exhibit only shallow trap-levels and although the grain boundaries have recently been shown to induce nonradiative decay, [ 19 ] regions only a few tens of nm away from the grain boundaries appear to be unaffected. [ 20,21 ] Furthermore, low Urbach energies, which are extracted from near band edge optical absorption measurements and serve as a benchmark for crystalline phase disorder, indicate low disorder and sharp band edges for lead tri-halide perovskites (15-23 meV). [ 22,23 ] All of these properties contribute to high open-circuit voltages, long charge-carrier lifetimes, and micrometer diffusion lengths, which are crucial for planar-hetero junction photovoltaics. [ 1,24 ] Nonetheless, these parameters are also expected to depend on the infl uence of crystallization condition on perovskite morphology in fabricated fi lms. [ 25 ] A distinct benefi t of organic-inorganic perovskite materials (e.g., over silicon) is that their bandgap can be tuned relatively easily with chemical composition, allowing attractive coloration and multijunction or tandem cell designs. For example, changing the metal cation at the M site from Pb 2+ to the less toxic Sn 2+ to form CH 3 NH 3 SnI 3 shifts the optical bandgap from 1.55 to 1.3 eV into the range of the "ideal" single-junction solar cell bandgap between 1.1 and 1.4 eV. [ 26,27 ] However, stability issues arising from the oxidation of tin have so far prevented widespread use. Alternatively, tuning the size of the A site cation has been proven to change optical and electronic properties of the perovskite and to signifi cantly infl uence solar cell performance. [ 28 ] Replacing MA in MAPbI 3 by the larger cation formamidinium HC(NH 2 ) 2 + (FA) was found to decrease the bandgap from 1.57 to 1.48 eV, [29][30][31] yield long photoluminescence (PL) lifetimes, high PCEs, [ 28 ] and lower recombination and device hysteresis. [ 32 ] Highest PCEs of 20.1% have been reported [12][13][14] to date for solar cells based on FAPbI 3 making this an attractive system to explore. In addition, the gradual replacement of the MA cation by FA through the fi lm was shown to create a mixed cation-lead-iodide PSC allowing for energetic gradients. [ 33 ] However, mixing of the halide component in the perovskite offers the fi nest tuning of the optical properties of the perovskite fi lm. Here, the mixed organic lead iodide/bromide system has recently gained strong interest for application in PSCs. [ 11,28 ] By changing the ratio between bromide and iodide (at the X site anion), the bandgap can be tailored between 1.55 eV (MAPbI 3 ) and 2.3 eV (MAPbBr 3 ), which results in the coverage of much of the visible spectrum and paves the way for the development of tandem solar cells. [ 11 ] In addition to MAPb(Br y I 1-y ) 3 , its formamidinium relative FAPb(Br y I 1-y ) 3 has been explored. [ 28 ] Most fractional mixtures of FAPb(Br y I 1-y ) 3 were found to be crystalline, with the exception of the region between y = 0.3 and Recent year...

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“…To the best of our knowledge, this is the highest carrier mobility for the perovskite PFETs. [17] The incorporation of Cs cation (Cs = 0%-30%) has notable effect on the performance of ambipolar triple cation PFETs.We have exposed freshly prepared PFETs to ambient air and monitored the p-and n-channel performance as a function of Organolead halide perovskites (ABX 3 where A is organic or inorganic cation, B is metal cation, and X is halogen anion) have significant attention as light absorber for highly efficient perovskite solar cells. Although having optimal bandgap, high absorption coefficient, and long-range exciton diffusion length, [1][2][3] methylammonium lead iodide (MAPbI 3 ) deteriorates at 85 °C due to the volatility of MA (methylammonium) cation.…”

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Ambipolar Triple Cation Perovskite Field Effect Transistors and Inverters

et al. 2016

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and inverters exhibit the best performance among perovskite PFETs. The present work demonstrates that triple cation perovskite can provide the ambipolar PFETs and complementary metal-oxide-semiconductor (CMOS)-like circuits for next generation, large-area microelectronics with low manufacturing cost.The PFETs with bottom contacts and a top gate were constructed by spin coating the triple cation precursor solution in anhydrous dimethylformamide:dimethylsulfoxide (DMF:DMSO) 4:1 (v:v) on the substrates (Figure 1a). The perovskite solution was deposited in two steps at 1000 and 6000 rpm for 10 and 30 s, respectively. Solvent treatment was conducted during the second step, where 100 µL chlorobenzene was poured on the spinning substrate followed by annealing at 100 °C for 1 h. Triple cation PFETs with various Cs amounts were fabricated, and their respective transfer and output characteristics are compared in Figures S1-S6 (Supporting Information). Figures S1-S6 (Supporting Information) illustrate transfer curves of the ambipolar triple cation PFETs, and I DS 1/2 versus V DS plot as a function of Cs cation. As Cs increased from 0% to 10%, the mobility increased monotonically from 1.95 × 10 −2 to 1.25 cm 2 V −1 s −1 for holes and from 4.81 × 10 −2 to 4.11 × 10 −2 cm 2 V −1 s −1 for electrons (Table S1, Supporting Information). However, no significant change in the charge-carrier mobilities was observed when Cs is higher than 15%. Figure 1b,c demonstrates the transfer characteristics for the p-and n-channel PFETs (Cs = 15%), respectively, with poly(methyl methacrylate) (PMMA) as a gate dielectric, in which ambipolar charge-transport characteristics were observed. Figure 1d,e represents the typical output characteristics with good current modulation. PMMA was selected since it can be processed at low temperature, soluble in a solvent orthogonal to triple cation, and contains negligible OH groups that could trap electrons. When V DS is low, the potential for the hole and electron injection cannot exceed the threshold voltage simultaneously. As a result, only one carrier can be accumulated, and the devices work in the unipolar model. Under these conditions, the transistors exhibit a very high I ON /I OFF ratio, typically higher than 10 4 at a high gate voltage (V GS = 130 V). The charge-carrier mobilities were determined using the drain current (I DS ) in the saturation region; Table S1 (Supporting Information) summarizes the maximum and average p-and n-channel mobilities. The maximum µ h and µ e mobilities are calculated to be 2.1 and 2.5 cm 2 V −1 s −1 , respectively. To the best of our knowledge, this is the highest carrier mobility for the perovskite PFETs. [17] The incorporation of Cs cation (Cs = 0%-30%) has notable effect on the performance of ambipolar triple cation PFETs.We have exposed freshly prepared PFETs to ambient air and monitored the p-and n-channel performance as a function of Organolead halide perovskites (ABX 3 where A is organic or inorganic cation, B is metal cation, and X is halogen anion) have signi...

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Organometallic Halide Perovskites: Sharp Optical Absorption Edge and Its Relation to Photovoltaic Performance

Cited by 2,242 publications

References 44 publications

Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells

Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells

Charge‐Carrier Dynamics and Mobilities in Formamidinium Lead Mixed‐Halide Perovskites

Ambipolar Triple Cation Perovskite Field Effect Transistors and Inverters

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