Limits...
The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells.

Chen Q, Zhou H, Fang Y, Stieg AZ, Song TB, Wang HH, Xu X, Liu Y, Lu S, You J, Sun P, McKay J, Goorsky MS, Yang Y - Nat Commun (2015)

Bottom Line: Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency.Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled.The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, USA [2] California NanoSystems Institute, University of California, Los Angeles, California 90095, USA.

ABSTRACT
Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%.

No MeSH data available.


Related in: MedlinePlus

Phase and morphology characterization of perovskite film.(a) XRD patterns corresponding to perovskite films fabricated with different approaches (from bottom to up: Reference, Samples 1 and 2). All three samples show similar crystal structure. (b–d) Top-view SEM images of perovskite films of Reference (b), Sample 1 (c) and Sample 2 (d). Reference and Sample 1 exhibit similar morphology in terms of polycrystalline texture and grain sizes, while Sample 2 presents a distinct film morphology when compared with Reference and Sample 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4490385&req=5

f2: Phase and morphology characterization of perovskite film.(a) XRD patterns corresponding to perovskite films fabricated with different approaches (from bottom to up: Reference, Samples 1 and 2). All three samples show similar crystal structure. (b–d) Top-view SEM images of perovskite films of Reference (b), Sample 1 (c) and Sample 2 (d). Reference and Sample 1 exhibit similar morphology in terms of polycrystalline texture and grain sizes, while Sample 2 presents a distinct film morphology when compared with Reference and Sample 1.

Mentions: XRD was conducted to characterize the crystal structure of each perovskite sample prepared on the TiO2-coated indium tin oxide (ITO) substrates (Fig. 2a). The perovskite films were prepared following the procedure that produces the optimized working device. It is found that both Samples 1 and 2 show similar crystal structures with distinctive (110), (220), (330) diffraction peaks centred at 14.2°, 28.3° and 42.9°, respectively. These peaks are in accordance with the major phases of CH3NH3PbI3, as shown in the Reference, regardless of the method of chlorine incorporation. However, Sample 1 showed slight difference in the diffraction profiles to that of the Reference, where the main peak slightly shifted to a higher degree. By assuming a tetragonal crystal structure in the perovskite, the calculated lattice parameter show ∼0.5% difference of the unit cell volume with respect to the Reference. This observation agrees with a previous claim that a CH3NH3PbI3 structure with a considerably low level of Cl doping is reasonable40. X-ray photoluminescence spectroscopy (XPS) was used to further examine the presence of Cl in the film (Supplementary Fig. 1). The resulting spectra revealed no detectable Cl signal in Sample 1 and the presence of a weak signal in Sample 2, results that are in agreement with recent characterizations of Cl in CH3NH3PbI3−xClx films283033. The rather small changes in lattice constant and scarcely detectable content of Cl clearly suggest that the incorporation of chlorine has negligible impact on the original crystal structure. Moreover, both Samples 1 and 2 exhibited the same diffraction intensity ratio for peaks, for example, (220)/(110), suggesting the similar crystal structure as compared to Reference. It indicates final products possess the same final phase ratios and domain orientation in the polycrystalline films, no matter what crystal growth/reorganization route has taken due to chlorine inclusion. The average crystal size for each sample, calculated according to the Scherrer's equation, was 45.7, 56.3 and 65.4 nm for the Reference, Sample 1 and Sample 2, respectively. In view of our result and previous work5, it would be carefully suggested to use CH3NH3PbI3(Cl) to denote the chemical formula of Samples 1 and 2 in this manuscript for more precise description of chemical composition and crystal structure.


The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells.

Chen Q, Zhou H, Fang Y, Stieg AZ, Song TB, Wang HH, Xu X, Liu Y, Lu S, You J, Sun P, McKay J, Goorsky MS, Yang Y - Nat Commun (2015)

Phase and morphology characterization of perovskite film.(a) XRD patterns corresponding to perovskite films fabricated with different approaches (from bottom to up: Reference, Samples 1 and 2). All three samples show similar crystal structure. (b–d) Top-view SEM images of perovskite films of Reference (b), Sample 1 (c) and Sample 2 (d). Reference and Sample 1 exhibit similar morphology in terms of polycrystalline texture and grain sizes, while Sample 2 presents a distinct film morphology when compared with Reference and Sample 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490385&req=5

f2: Phase and morphology characterization of perovskite film.(a) XRD patterns corresponding to perovskite films fabricated with different approaches (from bottom to up: Reference, Samples 1 and 2). All three samples show similar crystal structure. (b–d) Top-view SEM images of perovskite films of Reference (b), Sample 1 (c) and Sample 2 (d). Reference and Sample 1 exhibit similar morphology in terms of polycrystalline texture and grain sizes, while Sample 2 presents a distinct film morphology when compared with Reference and Sample 1.
Mentions: XRD was conducted to characterize the crystal structure of each perovskite sample prepared on the TiO2-coated indium tin oxide (ITO) substrates (Fig. 2a). The perovskite films were prepared following the procedure that produces the optimized working device. It is found that both Samples 1 and 2 show similar crystal structures with distinctive (110), (220), (330) diffraction peaks centred at 14.2°, 28.3° and 42.9°, respectively. These peaks are in accordance with the major phases of CH3NH3PbI3, as shown in the Reference, regardless of the method of chlorine incorporation. However, Sample 1 showed slight difference in the diffraction profiles to that of the Reference, where the main peak slightly shifted to a higher degree. By assuming a tetragonal crystal structure in the perovskite, the calculated lattice parameter show ∼0.5% difference of the unit cell volume with respect to the Reference. This observation agrees with a previous claim that a CH3NH3PbI3 structure with a considerably low level of Cl doping is reasonable40. X-ray photoluminescence spectroscopy (XPS) was used to further examine the presence of Cl in the film (Supplementary Fig. 1). The resulting spectra revealed no detectable Cl signal in Sample 1 and the presence of a weak signal in Sample 2, results that are in agreement with recent characterizations of Cl in CH3NH3PbI3−xClx films283033. The rather small changes in lattice constant and scarcely detectable content of Cl clearly suggest that the incorporation of chlorine has negligible impact on the original crystal structure. Moreover, both Samples 1 and 2 exhibited the same diffraction intensity ratio for peaks, for example, (220)/(110), suggesting the similar crystal structure as compared to Reference. It indicates final products possess the same final phase ratios and domain orientation in the polycrystalline films, no matter what crystal growth/reorganization route has taken due to chlorine inclusion. The average crystal size for each sample, calculated according to the Scherrer's equation, was 45.7, 56.3 and 65.4 nm for the Reference, Sample 1 and Sample 2, respectively. In view of our result and previous work5, it would be carefully suggested to use CH3NH3PbI3(Cl) to denote the chemical formula of Samples 1 and 2 in this manuscript for more precise description of chemical composition and crystal structure.

Bottom Line: Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency.Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled.The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, USA [2] California NanoSystems Institute, University of California, Los Angeles, California 90095, USA.

ABSTRACT
Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%.

No MeSH data available.


Related in: MedlinePlus