Limits...
Insight into Evolution, Processing and Performance of Multi-length-scale Structures in Planar Heterojunction Perovskite Solar Cells.

Huang YC, Tsao CS, Cho YJ, Chen KC, Chiang KM, Hsiao SY, Chen CW, Su CJ, Jeng US, Lin HW - Sci Rep (2015)

Bottom Line: The result is complementary to the currently microscopic study.The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance.The result can provide the insight into formation mechanism and rational synthesis design.

View Article: PubMed Central - PubMed

Affiliation: Institute of Nuclear Energy Research, Longtan, Taoyuan 32546, Taiwan.

ABSTRACT
The structural characterization correlated to the processing control of hierarchical structure of planar heterojunction perovskite layer is still incomplete due to the limitations of conventional microscopy and X-ray diffraction. This present study performed the simultaneously grazing-incidence small-angle scattering and wide-angle scattering (GISAXS/GIWAXS) techniques to quantitatively probe the hierarchical structure of the planar heterojunction perovskite solar cells. The result is complementary to the currently microscopic study. Correlation between the crystallization behavior, crystal orientation, nano- and meso-scale internal structure and surface morphology of perovskite film as functions of various processing control parameters is reported for the first time. The structural transition from the fractal pore network to the surface fractal can be tuned by the chloride percentage. The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance. The result can provide the insight into formation mechanism and rational synthesis design.

No MeSH data available.


(a) GISAXS profiles of the perovskite films prepared with 20% of chloride at 75 °C for 1, 5, 10, 15, 60 min, respectively. (b) Two dimensional GIWAXS patterns corresponding to Fig. 9a.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4559897&req=5

f9: (a) GISAXS profiles of the perovskite films prepared with 20% of chloride at 75 °C for 1, 5, 10, 15, 60 min, respectively. (b) Two dimensional GIWAXS patterns corresponding to Fig. 9a.

Mentions: From the mechanistic viewpoint, it is interesting to understand how both the film morphology and crystallization concurrently evolve with annealing time. The GISAXS profiles and 2D GIWAXS patterns of the perovskite films prepared with 20% of chloride at 100 °C for 1, 5, 10, 15, 60 min, respectively, are shown in Fig. 9. The GISAXS profiles annealed for 1 and 5 min have the characteristic of surface fractal morphology with surface fractal dimension of Ds = 2.6 (α = 3.4). Their morphology is very similar and may be similar to one before annealing. They seem to be almost stable to the annealing time. The GIWAXS measurement presented here is of much higher resolution compared to the previous measurement because a new 2D high-efficiency detector was adopted here and the experimental technique was updated. The corresponding GIWAXS pattern of the film annealed for 1 min (Fig. 9b) shows the so-called “crystalline precursor structure”, which is consistent with that observed by the other group23. This structure partly has the typical perovskite structure with the (110) and (220) spots at Q = 10 and 20 nm−1. There is also a distinctive set of scattering spots at lower Q values (<9 nm−1; as indicated in Fig. 9b). The corresponding GIWAXS pattern of the film annealed for 5 min shows the increasing crystallinity of perovskite structure. The peaks at lower Q region of the “crystalline precursor structure” disappear and accompany with the formation of the other precursor peak23 at Q = 11 nm−1. However, there additionally appears a signature peak of PbI2 at Q = 9 nm−1, revealing the occurrence of decomposition. This decomposition situations occurring for the short annealing time for the solution-processed perovskite film and at the low substrate temperature for the vacuum-deposited perovskite film (presented in this study) may be due to the oxygen and humidity during handling in the air1923. Their common point is the insufficient thermal effect. It can be explained that the incomplete crystallization has more paths to allow the entrance of oxygen and humidity. The GISAXS profiles annealed for 10, 15 and 60 min have the similar characteristic of surface fractal morphology with fractal dimension of Ds = 2.3 (α = 3.7). It seems that the morphological evolution of these films get into the other regime (Fig. 9a), different from those annealed for short times (1 & 5 min). Their corresponding GIWAXS patterns and intensities show the stable and complete crystallization. It agrees with the kinetic theory that the development of crystallization tends to be saturation. The PCE values of the devices based on the films annealed for 5, 10 and 15 min are 11, 13.8 and 12.7%, respectively. (J-V curves and EQE spectra are in the Supporting Information, Figure S2). The device based on the film annealed for 5 min has the lower PCE due to the incomplete crystallization. However, The PCE values decreases with the annealing time starting from 10 min (the optimum condition). Because their crystallinities are almost the same, the reduction in PCE may be attributed to the morphological change. According to the GISAXS result (Fig. 9a), the surface fractal dimension gradually increases (the slope of power-law scattering curves decreases) with the annealing time from 10 min to 60 min. It reflects the surface roughness becomes larger; suggesting that smooth interface in the full-coverage perovskite film with complete crystallization is favorable to the performance. This present study demonstrates that GISAXS/GIWAXS characterization can provide the complementary information to the usual XRD and microscopic results.


Insight into Evolution, Processing and Performance of Multi-length-scale Structures in Planar Heterojunction Perovskite Solar Cells.

Huang YC, Tsao CS, Cho YJ, Chen KC, Chiang KM, Hsiao SY, Chen CW, Su CJ, Jeng US, Lin HW - Sci Rep (2015)

(a) GISAXS profiles of the perovskite films prepared with 20% of chloride at 75 °C for 1, 5, 10, 15, 60 min, respectively. (b) Two dimensional GIWAXS patterns corresponding to Fig. 9a.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4559897&req=5

f9: (a) GISAXS profiles of the perovskite films prepared with 20% of chloride at 75 °C for 1, 5, 10, 15, 60 min, respectively. (b) Two dimensional GIWAXS patterns corresponding to Fig. 9a.
Mentions: From the mechanistic viewpoint, it is interesting to understand how both the film morphology and crystallization concurrently evolve with annealing time. The GISAXS profiles and 2D GIWAXS patterns of the perovskite films prepared with 20% of chloride at 100 °C for 1, 5, 10, 15, 60 min, respectively, are shown in Fig. 9. The GISAXS profiles annealed for 1 and 5 min have the characteristic of surface fractal morphology with surface fractal dimension of Ds = 2.6 (α = 3.4). Their morphology is very similar and may be similar to one before annealing. They seem to be almost stable to the annealing time. The GIWAXS measurement presented here is of much higher resolution compared to the previous measurement because a new 2D high-efficiency detector was adopted here and the experimental technique was updated. The corresponding GIWAXS pattern of the film annealed for 1 min (Fig. 9b) shows the so-called “crystalline precursor structure”, which is consistent with that observed by the other group23. This structure partly has the typical perovskite structure with the (110) and (220) spots at Q = 10 and 20 nm−1. There is also a distinctive set of scattering spots at lower Q values (<9 nm−1; as indicated in Fig. 9b). The corresponding GIWAXS pattern of the film annealed for 5 min shows the increasing crystallinity of perovskite structure. The peaks at lower Q region of the “crystalline precursor structure” disappear and accompany with the formation of the other precursor peak23 at Q = 11 nm−1. However, there additionally appears a signature peak of PbI2 at Q = 9 nm−1, revealing the occurrence of decomposition. This decomposition situations occurring for the short annealing time for the solution-processed perovskite film and at the low substrate temperature for the vacuum-deposited perovskite film (presented in this study) may be due to the oxygen and humidity during handling in the air1923. Their common point is the insufficient thermal effect. It can be explained that the incomplete crystallization has more paths to allow the entrance of oxygen and humidity. The GISAXS profiles annealed for 10, 15 and 60 min have the similar characteristic of surface fractal morphology with fractal dimension of Ds = 2.3 (α = 3.7). It seems that the morphological evolution of these films get into the other regime (Fig. 9a), different from those annealed for short times (1 & 5 min). Their corresponding GIWAXS patterns and intensities show the stable and complete crystallization. It agrees with the kinetic theory that the development of crystallization tends to be saturation. The PCE values of the devices based on the films annealed for 5, 10 and 15 min are 11, 13.8 and 12.7%, respectively. (J-V curves and EQE spectra are in the Supporting Information, Figure S2). The device based on the film annealed for 5 min has the lower PCE due to the incomplete crystallization. However, The PCE values decreases with the annealing time starting from 10 min (the optimum condition). Because their crystallinities are almost the same, the reduction in PCE may be attributed to the morphological change. According to the GISAXS result (Fig. 9a), the surface fractal dimension gradually increases (the slope of power-law scattering curves decreases) with the annealing time from 10 min to 60 min. It reflects the surface roughness becomes larger; suggesting that smooth interface in the full-coverage perovskite film with complete crystallization is favorable to the performance. This present study demonstrates that GISAXS/GIWAXS characterization can provide the complementary information to the usual XRD and microscopic results.

Bottom Line: The result is complementary to the currently microscopic study.The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance.The result can provide the insight into formation mechanism and rational synthesis design.

View Article: PubMed Central - PubMed

Affiliation: Institute of Nuclear Energy Research, Longtan, Taoyuan 32546, Taiwan.

ABSTRACT
The structural characterization correlated to the processing control of hierarchical structure of planar heterojunction perovskite layer is still incomplete due to the limitations of conventional microscopy and X-ray diffraction. This present study performed the simultaneously grazing-incidence small-angle scattering and wide-angle scattering (GISAXS/GIWAXS) techniques to quantitatively probe the hierarchical structure of the planar heterojunction perovskite solar cells. The result is complementary to the currently microscopic study. Correlation between the crystallization behavior, crystal orientation, nano- and meso-scale internal structure and surface morphology of perovskite film as functions of various processing control parameters is reported for the first time. The structural transition from the fractal pore network to the surface fractal can be tuned by the chloride percentage. The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance. The result can provide the insight into formation mechanism and rational synthesis design.

No MeSH data available.