Fe3+ Doped into MAPbCl3 Single Crystal: Impact on Crystal

Subscriber access provided by UNIV OF LOUISIANA

C: Energy Conversion and Storage; Energy and Charge Transport 2+

3+

3

Fe /Fe Doped into MAPbCl Single Crystal: Impact on Crystal Growth, Optical and Photoelectronic Properties Xiaohua Cheng, Lin Jing, Ye Yuan, Songjie Du, Jun Zhang, Xiaoyuan Zhan, Jianxu Ding, Hao Yu, and Guodong Shi J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b12428 • Publication Date (Web): 04 Jan 2019 Downloaded from http://pubs.acs.org on January 8, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Fe2+/Fe3+ Doped into MAPbCl3 Single Crystal: Impact on Crystal Growth, Optical and Photoelectronic Properties Xiaohua Cheng 1, Lin Jing 1, Ye Yuan 1, Songjie Du 1, Jun Zhang 1, Xiaoyuan Zhan 1, Jianxu Ding*, 1, Hao Yu*, 2, Guodong Shi 3 1. College of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China; 2. College of Chemical and Environmental Engineering, Shandong University of Science and Technology, 266590, Qingdao, China; 3. Taishan University, 271000, Taian, China *Corresponding author: E-mail: [email protected] (J. X. Ding); [email protected] (H. Yu)

1

ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

ABSTRACT: As one type of organic-inorganic hybrid lead halide perovskites, MAPbX3 has attracted immense interests in applications of optoelectronic devices because of their remarkable properties. However, the toxicity lead is considered as the biggest concerns which cause environment pollutions. The introduction of impurity ions deliberately to replace Pb in crystal structure is deemed to an effective way to minimize the effect of lead toxicity while maximizing energy conversion efficiency. On the other hand, iron (Fe) impurities are inevitable impurities presenting in raw materials. However, the influence of Fe ions on both crystal structure and photoelectric properties is still unknown. So, it is worth exploring the effects of heterovalent Fe2+/Fe3+ on hybrid lead halide perovskite. Here, we firstly incorporate Fe2+/Fe3+ into the crystal lattice of MAPbCl3 single crystals, and successfully grown MAPbCl3 single crystals with various doping concentrations of Fe2+/Fe3+ (0, 10, 20%), and report the crystal growth process, crystal structures and optical properties of MAPbCl3 single crystals doped with Fe2+/Fe3+. Moreover, the effect of Fe2+/Fe3+ incorporated into MAPbCl3 single crystals on the optoelectronic properties were investigated by utilizing planar photo-detectors.

2


Page 3 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction The outstanding optoelectronic properties of organic-inorganic hybrid lead halide perovskites, such as direct optical band gap, large optical absorption coefficient, long-range diffusion lengths and high charge carrier mobility,

1-7

have led to their

rapid enhancement in the power conversion efficiency (PCS) and enormous potential in solar cells and optoelectronic applications.8-10 After several years of booming development, the energy conversion efficiency of hybrid lead halide perovskite based solar cell has been improved to 23.2% till now.11 Especially, hybrid methylamine lead halide (MAPbX3, MA=CH3NH3+, X=Cl, Br, I) has attracted immense attention for solar cells, photodetectors, lasing, light-emitting diodes and hydrogen production.12-15 The

perovskites-based

photodetectors,

particularly,

have

been

intensively

investigated,16-18 and revealing the promising properties in terms of high detectivity and fast response speed. Although such hybrid all most of Pb-based perovskite have lots of high performance mentioned above, but one of the biggest concerns with this type of materials is the toxicity of lead which lead to damage upon both human and environment.19-23 Lead-free perovskites were now considered to be the new frontier that deserves special attention for development of perovskite materials. Therefore, finding alternative elements of lead with good performance is especially critical. According to previous reports, the element Pb could be fully or partially replaced by Bi,24 Sn,25-27 Ge,28 Sb,29 or other transition metals (e. g. Fe, Cu, Mn).30-34 However, the optoelectronic performance of the lead-free perovskites based devices is not as 3



Page 4 of 28

satisfactory as expectation. Therefore, partially replacement of Pb by other cations is proposed to decrease toxicity from Pb, and to optimize the photoelectric properties. For instance, 50% Sn-based planar perovskite solar cell was successfully designed and its PCE reached to 13.6%.35 In addition, there are many reports on the effects that the incorporation of metal cations on the synthesis, properties and optoelectronic applications of perovskite,36-38 as well as the effects of heterovalent doping in organic-inorganic metal halide perovskite crystals.39,40 These have given us a lot of inspiration. Fe ions (both Fe2+ and Fe3+), one of the most abundant elements on earth, exhibit excellent characterizations, such as good conductivity, low cost, environment friendly, etc. In theory, the gradual realization of replacing lead ions with iron ions is a worthy research direction to pursue energy efficiency while avoiding lead toxicity. On the other hand, irons (Fe) are inevitable impurities in raw materials for synthesis of hybrid perovskites,41 but till now, there is still lacking systematic investigation about how Fe2+/Fe3+ affects perovskites, such as, increasing crystal stability,42 impacting electronic transport and limiting charge-carrier lifetimes.43-45 Therefore, it is worth exploring the effects of heterovalent Fe2+/Fe3+ on organic-inorganic metal halide perovskite crystals. In the present work, we choose MAPbCl3 as the target, and large scale MAPbCl3 single crystals with various concentrations of Fe2+/Fe3+ were harvested by adjusting the concentrations of Fe2+/Fe3+ in growth solutions, respectively. Here, we demonstrate and discuss the influence of Fe2+/Fe3+ on MAPbCl3 single crystal growth process, crystal structures, optical properties and optoelectronic properties. Especially, 4


Page 5 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the incorporation of Fe2+/Fe3+ into crystal lattice and ionic transportation performances are discussed as well. In addition, planar photo-detectors based on MAPbCl3 single crystals with various Fe2+/Fe3+ concentrations were fabricated and the optoelectronic properties of MAPbCl3 doped with Fe2+/Fe3+ were compared.

Experimental section Growth of MAPbCl3 single crystals doping with Fe2+/Fe3+ According to previous reports,46,47 pure MAPbCl3 single crystals can be grown by dissolving stoichiometric amounts of PbCl2 and MACl in mixed solvent of DMSO and DMF (Volume ratio DMSO:DMF=1:1). This single crystal growth method was chosen to grow MAPbCl3 single crystals doping with Fe2+/Fe3+ as well. In our experiments, in order to grow MAPbCl3 single crystals with Fe2+/Fe3+, FeCl2·4H2O and FeCl3·6H2O were added to the precursor solutions (1 M). As shown in Figure 1(a), it can be observed that the precursor solutions doped with FeCl2·4H2O and FeCl3·6H2O appear red-brown and orange-yellow, respectively. Then, the precursor solutions were sealed and maintained at 60℃ for 7~9 days, and small cubic MAPbCl3 single crystals doped with Fe2+/Fe3+ with sizes of 2~5mm were harvested, as displayed in Figure 1(b). It is worth mentioning that the contents of Fe2+/Fe3+ were controlled by varying the doping concentration of FeCl2/FeCl3 in precursor solutions.

5



Page 6 of 28

Fabrications of photo-detectors Planar photo-detectors were fabricated on (100) facets of MAPbCl3 single crystals doped with Fe2+/Fe3+. Firstly, the surface was well-polished by using dried silk in order to minimize the effects of surface decomposition, hydration and pollutants on optoelectronic properties. And then, the alloy hollow contact pattern masks were laid on the polished (100) facets of MAPbCl3 single crystals doped with Fe2+/Fe3+ as soon as possible. Ultimately, the Au electrodes were formed on the blank area of the hollowed mask after the sputtering processes were carried out. It should be mentioned that the width of light absorption area was designed as 1 mm.

Characterizations and measurements The powder X-ray diffraction of MAPbCl3 single crystals doped with Fe2+/Fe3+ were carried out under a D/Max2500PC X-ray diffractometer with Cu KαI irradiation at 40 kV and 100 mA. The UV-vis absorption spectra of MAPbCl3 single crystals doped with Fe2+/Fe3+ were obtained by a UV-2550 spectrometer with an integrating sphere in the range of 250-800 nm. The surface morphology and elemental analysis of MAPbCl3 single crystal doped with Fe2+/Fe3+ were performed using field-emission scanning electron microscope (SEM), coupled with Energy-dispersive X-ray spectroscopy (EDS). A series of photocurrents of the planar photo-detectors based on MAPbCl3 single crystals doped with Fe2+/Fe3+ were obtained by using a semiconductor measurement system (Keithley 2450) under the irradiation of laser diode with excitation wavelength 6


Page 7 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


of 405 nm. Besides, the continuous on-off photocurrents under various applied voltages were harvested through setting the on-off interval time (10 s). The whole measurements were conducted in dark space in order to eliminate the effect of light on experimental. The optoelectronic properties of MAPbCl3 single crystals doped with Fe2+/Fe3+ were compared with pure MAPbCl3 single crystals.

Results and discussion Figure 1(b-c) presents the photographs of MAPbCl3 single crystals doped with various Fe2+/Fe3+ concentrations (0%, 10%, 20%), respectively. After carefully measurement, the thickness of pure MAPbCl3 single crystals are 3mm, and MAPbCl3 single crystals doped Fe2+/Fe3+ are about 2mm. Obviously, the transparent cubic MAPbCl3 single crystals present colorful, and the color becomes deeper as a rise of doping concentrations of Fe2+/Fe3+. In detail, the color of Fe2+ doped MAPbCl3 single crystal is brown, while the Fe3+ doped crystal exhibits pale yellow, in good agreement with the solution color dissolved with Fe2+ or Fe3+. This gives apparent proof that both Fe2+ and Fe3+ have successfully entered into crystal lattice of MAPbCl3 single crystal. Furthermore, the color of precursor solution of MAPbCl3 doped with Fe2+/Fe3+ matches that of MAPbCl3 doped with Fe2+/Fe3+ single crystals, so we think the valence of Fe2+/Fe3+ in crystal are not changed during the process of crystal growth. To reveal the concrete Fe2+ and Fe3+ contents and elemental distribution in crystal lattice, EDS were carried out, which were shown in Figure S1. The detail Fe2+/Fe3+ contents in the corresponding doped MAPbCl3 single crystals are shown in 7



Page 8 of 28

Figure 1(d), and which gives clear evidence that the Fe3+ contents are higher than Fe2+ for the equivalent doping concentrations in growth solutions. The easier accessible into crystal of Fe3+ brings more macroscopic defects in crystals even causes cracks. As shown in Figure 1(c), the 20% Fe3+ doped MAPbCl3 single crystal displays opaque, with some macroscopic defects in it. We also grew some MAPbCl3 single crystals doped with 50% Fe3+ in growth solutions, which are shown in Figure S2. It also proves that Fe3+ could causes crystal cracks.

8


d5 4

MAPbCl3-Fe

2+

MAPbCl3-Fe

3+

4.42

e 3.3

MAPbCl3-Fe MAPbCl3-Fe

3.2

3.21 3 2

3.13

0.36 0

0.61

10% 20% Doping concentration()

2.9

3+

3.11

3

3.0

1

2+

3.18

3.1

2+

3+

Fe /Fe contents()

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Stoichiometric ratio of Cl:Pb

Page 9 of 28

10% 20% Doping concentration(%)

Figure 1(a) Precursor solutions dissolved with FeCl2·4H2O and FeCl3·6H2O, respectively. (b-c) Photos of MAPbCl3 single crystals doped with various concentrations of Fe2+ and Fe3+. (d-e) Histograms of Fe2+/Fe3+ contents and stoichiometric ratio of Cl to Pb in Fe2+/Fe3+ doped MAPbCl3 single crystals.

The existences of Fe2+/Fe3+ in single crystal have two possible sites after entering into crystal lattice: at the positions of Pb2+ or MA+. To reveal the real positions of Fe2+/Fe3+ in single crystal, the concrete stoichiometric ratios of Cl: Pb of MAPbCl3 doped with various concentration Fe2+/Fe3+ are shown in Figure 1(e) as a histogram. By comparing the atomic percentages of various elements, the ratios of Cl: Pb in pure MAPbCl3 single crystal is 3.0, while they reach to 3.13 (10%) and 3.18 (20%) in Fe2+ doped MAPbCl3 single crystals. The deficiency of Pb element suggests that Pb2+ being replaced by Fe2+. However, the incorporation of Fe3+ into crystal lattice is quite different from that of Fe2+. The ratio of Cl: Pb is 3 and 3.11 in 10% and 20% Fe3+ doped single crystals, respectively. It seems that the incorporation capacity of Fe3+ is 9



Page 10 of 28

not as excellent as Fe2+. However, the EDS data show that more Fe3+ is in existence than Fe2+. Thus, we believe that Fe2+ replaces only Pb2+ after entering into crystal lattice and results that the percentage of Pb decreases as the increase of concentration of doped Fe2+. Besides, combined with the optoelectronic performance we conducted later, it can be seen that the dark current of MAPbCl3 doped with Fe2+ single crystal did not increase much. This confirms that Fe2+ replaces only Pb2+ after entering into crystal lattice. As for Fe3+, the lower Cl: Pb ratio and the higher Fe contents than Fe2+ in single crystals, implies that it is difficult to replace Pb2+ by Fe3+ in MAPbCl3 single crystal. This is attributed to the higher chemical valence of Fe3+ than Pb2+. The crystal structure is displayed in Figure S3, once a Pb2+ is replacing by a Fe3+, the [PbCl6]4would change to [FeCl6]3-. The nonequivalent octahedral brings single crystal to collapse because Pb plays a pivotal role in the crystal structure. On the side, the ratio of Cl: Pb is 3 in MAPbCl3 doped with 10% Fe3+ single crystals also indicated Pb2+ has not replaced by Fe3+, but there is still a part of Fe3+ that replaces Pb2+ when the Fe3+ doping concentration is high. For example, the ratio of Cl: Pb is 3.11 in MAPbCl3 single crystals doped with 20% Fe3+. Thus, these data explain that Fe3+ replaces MA+ when low doping concentration of Fe3+ enters the lattice of MAPbCl3 single crystal, accompanied with vacancies MA+, while Fe3+ replaces Pb2+ under high doping concentration of Fe3+. In terms of optoelectronic performance, it is manifested by an increase of internal carriers and dark-current we obtained later.

10


Page 11 of 28

a

b

MAPbCl3-10%Fe2+ a=5.6871Å Pure MAPbCl3 a=5.6768Å 20

30

40 2

50

3+

MAPbCl3-20%Fe a=5.6910Å

Intensity(a.u.)

Intensity(a.u.)

MAPbCl3-20%Fe2+ a=5.6881Å

10

3+

MAPbCl3-10%Fe a=5.6907Å

Pure MAPbCl3 a=5.6768Å

60

70

10

20

30

40 2

50

60

70

c 2+

Intensity(a.u.)

20%Fe

2+

10%Fe

Pure 14.5 15.0 15.5 16.0 16.5 21.5

22.0

22.5 34.5 35.0 35.5 36.0 36.5 45

2

46

47

48

46

47

48

d 3+

Intensity(a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


20%Fe

3+

10%Fe

Pure 14.5 15.0 15.5 16.0 16.5

21.5

22.0

22.5

34.5 35.0 35.5 36.0 36.5

2

45

11



Page 12 of 28

Figure 2(a-b) Powder XRD patterns of MAPbCl3 single crystal with different Fe2+/Fe3+ doping concentrations. (c-d) Magnified view of XRD patterns, respectively.

The powder XRD characterizations of MAPbCl3 doped with various Fe2+/Fe3+ concentrations are displayed in Figure 2(a-b). All the samples are in excellent agreement with the pure cubic MAPbCl3 XRD pattern as previous reports,5, 46-47 and the space group is assigned to Pm3̅m. According to the XRD data, no impurities are detected which suggests both Fe2+ and Fe3+ are successfully entered into crystal lattice. Interestingly, we discover that almost all the peaks of MAPbCl3 doped with Fe2+/Fe3+ shift to small angles than pure MAPbCl3, which is clearly shown in the corresponding local magnified views of XRD patterns in Figure 2(c-d). According to the Bragge equation 2dsinθ=nλ, the shift to small diffraction angles implies that both Fe2+ and Fe3+ bring lattice expansion. After fitting the powder XRD data, the unit cell parameters were calculated and listed in Figure 2(a-b). We found that the unit cell parameters become larger as an increase of Fe2+/Fe3+ doped concentrations. Moreover, the unit cell parameters of Fe3+ doped MAPbCl3 are larger than those of doped with equivalent Fe2+. These confirms that the incorporation of Fe2+/Fe3+ leads to lattice expansion, and the incorporation of Fe3+ is more influential than Fe2+. We believe that the lattice expansion brought by Fe2+/Fe3+ is attributed to the lattice distortion and octahedral distortion after Fe2+/Fe3+ replacing Pb2+ and MA+. For instance, the single crystal doping with 20% Fe3+ exhibits macroscopic cracks might be caused by large lattice expansions. 12


Page 13 of 28

a

b

Pure MAPbCl3

Pure MAPbCl3 MAPbCl3-10Fe

2+

MAPbCl3-20Fe

2+

MAPbCl3-20Fe

3+

Absorption(a.u.)

Absorptuion(a.u.)

MAPbCl3-10Fe

2+

465nm 436nm 300

c

400

436nm 447nm

500nm 500

600

700

Wavelength(nm)

d

800

300

d

Pure MAPbCl3 MAPbCl3-10Fe2+

400

500

600

700

Wavelength(nm)

800

Pure MAPbCl3 2+

MAPbCl3-10Fe

MAPbCl3-20Fe3+

3+

MAPbCl3-20Fe

Normalized

Normalized

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.75eV

2.45eV 1

2

2.81eV 3

hveV

2.75eV 4

5

1

2

2.81eV 3

hv(eV)

4

5

Figure 3(a-b) UV-vis absorption spectra, (c-d) Band gaps of MAPbCl3 single crystals doped with Fe2+/Fe3+, respectively.

The UV-vis absorption spectra of MAPbCl3 doped with Fe2+/Fe3+ single crystals were displayed in Figure 3(a-b), respectively. Apparently, a red-shift occurs according to the absorption edges of MAPbCl3 doped with Fe2+/Fe3+ single crystal compared with pure MAPbCl3 single crystal. The influence of Fe2+ on optical absorption is greater than that of Fe3+. In detail, the absorption edges of pure MAPbCl3, MAPbCl3-10% Fe2+ and MAPbCl3-20% Fe2+ are at 436, 465 and 500 nm, respectively. 13



While the absorption edges of MAPbCl3 doped with Fe3+ single crystal are all at about 447 nm. Moreover, the absorption between 500-800 nm is greatly enhanced after Fe2+ entering into crystal lattice, and this phenomena after doping with Fe3+ is not as obvious as doping with Fe2+. According to the optical absorption spectra, the band gaps of pure MAPbCl3, MAPbCl3-10% Fe2+ and MAPbCl3-20% Fe2+ are calculated as 2.81, 2.75 and 2.45 eV, respectively. The band gaps of MAPbCl3 single crystal doped with Fe3+ are 2.75 eV, as shown in Figure 3(c-d). These data further demonstrated that Fe2+ and Fe3+ in crystal lattice behave different approaches to its band structures. Remarkably, both the absorption edge and band gap revealed that MAPbCl3 doped with Fe2+/Fe3+ single crystal has a wider absorption spectrum and a smaller optical band gap than pure MAPbCl3 single crystal, which means that MAPbCl3 doped with Fe2+/Fe3+ single crystal as light harvester can utilize more sunlight in photovoltaic field.

b CurrentA

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 28

Pure MAPbCl3 MAPbCl3-10%Fe2+

0.2

MAPbCl3-10%Fe3+

0.0

-0.2 -0.4

-4

-2

0

2

4

Voltage(V)

Figure 4(a) Schematic diagram of planar photo-detector structure. (b) Dark currents of pure MAPbCl3, MAPbCl3 doped with 10% Fe2+ and 10% Fe3+, respectively.

14


Page 15 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In order to explore the influence of Fe2+/Fe3+ on optoelectronic performances of MAPbCl3 single crystal, planar photo-detectors based on pure MAPbCl3, 10% Fe2+ and 10% Fe3+ doped MAPbCl3 single crystals were fabricated, respectively. Figure 4(a) manifests the schematic diagram of planar photo-detector structure. As shown in Figure 4(a), the exposed crystal surface with width of 1 mm was irradiated under 405 nm laser and the Au electrodes covered the crystal surface were connected with the semiconductor

measurement

system

through

probes.

The

photograph

of

photo-detector prepared well was displayed in Figure S4. A series of dark-currents and photo-currents were collected based photo-detectors of MAPbCl3 single crystal doped with Fe2+/Fe3+. In Figure 4 (b), the dark currents of pure MAPbCl3, doped with 10% Fe2+ and 10% Fe3+ single crystals based photo-detectors are compared. It can be seen that the dark-currents of pure MAPbCl3 and MAPbCl3 doped with 10% Fe2+ are almost the same, indicating that Fe2+ has little effect on intrinsic carriers (electron-hole pairs generated by thermal excitation) after replacing Pb2+ in crystal lattice. However, the dark current of 10% Fe3+ doped MAPbCl3 is an order of magnitude enhanced. The larger dark current of 10% Fe3+ doped MAPbCl3 implies that it possesses a stronger charge transportation capacity. We believe that the larger dark current of 10% Fe3+ doped MAPbCl3 is attributed to the replacement of MA+ with Fe3+ that causes more MA+ vacancies.

15



a

b 0.08

Pure MAPbCl3

MAPbCl3-Fe

c

2+

MAPbCl3-Fe3+

1.0

0.06

Current(A)

2 0.5

Current(A)

0.04

Current(uA)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 28

0.0

0.02

0

0.00

Dark 0.5mW 1mW 2mW 3mW

-2

-4

-2

0

Voltage(V)

2

4

-0.5


-0.02

-0.04

-4

-2

0

Voltage(V)

2


-1.0

2.2v

-1.5

4

-4

-2

0

Voltage(V)

2

4

Figure 5(a-c) The photo-current curves of photo-detector based MAPbCl3 doped with 0% Fe, 10% Fe2+ and 10% Fe3+ single crystal, respectively.

Figure 5(a-c) displays the photo-currents of photo-detectors based on pure MAPbCl3, doped with 10% Fe2+ and 10% Fe3+ single crystals under various illumination powers using a 405 nm semiconductor laser, respectively. The photo-currents increased with rise of voltages and illumination powers. Moreover, we noticed that the photo-currents of MAPbCl3 doped with 10% Fe2+ are much smaller than pure MAPbCl3 and MAPbCl3 doped with 10% Fe3+. In detail, the photo-current of MAPbCl3 doped with 10% Fe2+ is 0.074 μA at an applied voltage of 5 V under illuminations power of 3 mW, whereas they are as high as 3.176 and 1.270 μA under the same conditions. This result implies that both Fe2+ replacing Pb2+ and Fe3+ replacing MA+ reduced the internal currieries. On the other hand, compared to the photo-currents of pure MAPbCl3 and MAPbCl3 doped with 10% Fe2+, the photo-current curves of MAPbCl3 doped with 10% Fe3+ exhibit inflexion points before which the photocurrents increase rapidly (low voltage region) and after which 16


Page 17 of 28

they increase slowly (high voltage region). It is obvious that the inflexion points of MAPbCl3 doped with 10% Fe3+ in Figure 5(c) appears at about 2.2 V. The appearance of inflection points is attributed to the increase of MA+ vacancy defects and resulting in intrinsic carriers being trapped by MA+ vacancies when incorporation of Fe3+ into MAPbCl3 crystal lattice. In addition, compared to the photo-currents of pure MAPbCl3, quite weak photo-currents of MAPbCl3 doped with 10% Fe2+ and Fe3+ single crystals occur when applied voltage was 0 V. We believe that the incorporation of Fe2+/ Fe3+ into MAPbCl3 single crystal brings more piled ion charges, which suppresses the excited electrons moving towards to the Au electrodes and generates built-in electric fields. The establishment of the built-in electric field depends on the doping concentration in some extent.48 This can be also seen from the comparison the dark-currents in Figure 4(b), this phenomenon is very obvious, especially the photo-currents of MAPbCl3 doped with 10% Fe3+.

a 0.20 Pure MAPbCl 1V

3

2V

3V

4V

5V

0.15

Current(A)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.10

0.05

0.00

Time(10s/div)

17



b 0.010 MAPbCl1V -10%Fe 2V Current(A)

3

2+

3V

4V

5V

0.005

0.000

c

Time(10s/div) MAPbCl3-10%Fe 1V

2V

3+

3V

4V

5V

0.03

Current(A)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 28

0.02

0.01

0.00

Time(10s/div)

Figure 6(a-c) Continuous five on-off circles under various applied voltages of the MAPbCl3 doped with 0%, 10% Fe2+ and 10% Fe3+ single crystals, respectively.

The switch feature is another important parameter to compare optoelectronic properties, which is revealed by the time-dependent photocurrent measurements at various applied voltages with an illumination wavelength of 405 nm. Figure 6(a-c) represents five continuous on-off circles under various applied voltages of photo-detectors under 2 mW power illuminations, and the time interval between on-off is 10 seconds. The amplification response features are displayed in Figure S5. For pure MAPbCl3 photo-detector, the photo-currents increase slowly at lower 18


Page 19 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


voltages (1-3V) and decrease at higher voltages (4-5V) when the illumination turns on. The switch features are different when Fe2+ and Fe3+ incorporating into crystal lattices. The photo-currents of MAPbCl3 doped with 10% Fe2+ reach to the maximum when the illumination turns on and slightly decrease under continuous illumination for all the measurement voltages. Whereas, it shows an obvious upward tendency when illumination turns on for MAPbCl3 doped with 10% Fe3+. On the other hand, the maximum on/off ratios of pure MAPbCl3 single crystals doped with 0%, 10% Fe2+ and 10% Fe3+ at 5 V are 45, 6 and 24, respectively.

Conclusions In conclusion, a series of MAPbCl3 single crystals doping with various concentrations of heterovalent Fe2+/Fe3+ (0, 10, 20%) were successfully grown. The incorporation of Fe2+/Fe3+ into crystal lattice leads to lattice expansion and brings MAPbCl3 single crystals colorful. Elemental analysis reveals that Fe2+ is prone to replacing Pb2+ in MAPbCl3 single crystal. Therefore, the optoelectronic properties are greatly deteriorated, embodying the lower photo-currents and on/off ratios. However, Fe3+ is inclined to replace MA+ and thereby causes more vacancies. Such defect makes a higher dark current and lower on/off ratios. Our results suggest that both Fe2+ and Fe3+ should be avoided in hybrid perovskite materials. Acknowledgements This work was financially supported by Natural Science Foundation of Shandong Province (ZR2016EMQ10), National Natural Science Foundation of China (No. 51202131 and 21805169). The authors declare no competing financial interest.

19



Page 20 of 28

Supporting Information The detail descriptions of MAPbCl3 single crystals doped with various concentrations of Fe2+/Fe3+, including the analysis of EDS, growth of doped 50% Fe2+/Fe3+ contents of MAPbCl3 single crystal, the structure diagram of MAPbCl3 single crystal, the photograph of photo-detector prepared well and the amplification response features are found in the supporting information.

References (1) Saidaminov, M. I.; Abdelhady, A. L.; Murali, B.; Alarousu, E.; Burlakov, V. M.; Peng, W.; Dursun, I.; Wang, L. F.; He, Y.; Maculan, G.; et al. High-Quality Bulk Hybrid Perovskite Single Crystals Within Minutes by Inverse Temperature Crystallization. Nat. commun. 2015, 6: 7586. (2) Zhu, X.; Su, H.; Marcus, R. A.; Michel-Beyerle, M. E. Computed and Experimental Absorption Spectra of The Perovskite CH3NH3PbI3. J. Phys. Chem. Lett. 2014, 5(17): 3061-3065. (3) Xing, G. C.; Mathews, N.; Sun, S. Y.; Lim, S. S.; Lam, Y. M.; Grätzel, M.; Mhaisalkar, S.; Sum, T. C. Long-Range Balanced Electron and Hole Transport Lengths in Organic-Inorganic CH3NH3PbI3. Science 2013, 342(6156): 344-347. (4) Shi, D.; Adinolfi, V.; Comin, R.; Yuan, M. J.; Alarousu, E.; Buin, A.; Chen, Y.; Hoogland, S.; Rothenberger, A.; Katsiev, K.; et al. Low Trap-State Density and Long Carrier Diffusion in Organolead Trihalide Perovskite Single Crystals. Science 2015, 347(6221): 519-522. 20


Page 21 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(5) Liu, Y. C.; Yang, Z.; Cui, D.; Ren, X. D.; Sun, J. K.; Liu, X. J.; Zhang, J. R.; Wei, Q. B.; Fan, H. B.; Yu, F. Y.; et al. Two‐Inch‐Sized Perovskite CH3NH3PbX3 (X= Cl, Br, I) Crystals: Growth and Characterization. Adv. Mater. 2015, 27(35): 5176-5183. (6) Tian, W. M.; Zhao, C. Y.; Leng, J.; Cui, R. R.; Jin, S. Y. Visualizing Carrier Diffusion in Individual Single-Crystal Organolead Halide Perovskite Nanowires and Nanoplates. J. Am. Chem. Soc. 2015, 137(39): 12458-12461. (7) Stranks, S. D.; Eperon, G. E.; Grancini, G.; Menelaou, C.; Alcocer, M. J. P.; Leijtens, T.; Herz, L. M.; Petrozza, A.; Snaith, H. J. Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in An Organometal Trihalide Perovskite Absorber. Science 2013, 342(6156): 341-344. (8) Correa-Baena, J. P.; Saliba, M.; Buonassisi, T.; Grätzel, M.; Abate, A.; Tress, W.; Hagfeldt, A. Promises and Challenges of Perovskite Solar Cells. Science 2017, 358(6364): 739-744. (9) Zhang, P.; Zhang, G. D.; Liu, L.; Ju, D. X.; Zhang, L. Z.; Cheng, K.; Tao, X. T. Anisotropic Optoelectronic Properties of Melt-Grown Bulk CsPbBr3 Single Crystal. J. Phys. Chem. Lett. 2018, 9(17): 5040-5046. (10)Zhao, Y. X.; Zhu, K. Organic–Inorganic Hybrid Lead Halide Perovskites for Optoelectronic and Electronic Applications. Chem. Soc. Rev. 2016, 45(3): 655-689.

21



Page 22 of 28

(11)Jeon, N. J.; Na, H.; Jung, E. H.; Yang, T. Y.; Lee, Y. G.; Kim, G.; Shin, H. W.; Seok, S.; Lee, J.; Seo, J. A Fluorene-Terminated Hole-Transporting Material for Highly Efficient and Stable Perovskite Solar Cells. Nat. Energy 2018: 3(8): 682. (12)Choi, J. J.; Yang, X. H.; Norman, Z. M.; Billinge, S. J. L.; Owen, J. S. Structure of Methylammonium Lead Iodide Within Mesoporous Titanium Dioxide: Active Material in High-Performance Perovskite Solar Cells. Nano. Lett. 2013, 14, 127-133. (13)Ding, J. X.; Du, S. J.; Zhao, Y.; Zhang, X. J.; Zuo, Z. Y.; Cui, H. Z.; Zhan, X. Y.; Gu, Y. J.; Sun, H. Q. High-Quality Inorganic-Organic Perovskite CH3NH3PbI3 Single Crystals for Photo-Detector Applications. J. Mater. Sci. 2017, 52, 276-284. (14)Chen, Y. S.; Manser, J. S.; Kamat, P. V. All Solution-Processed Lead Halide Perovskite-BiVO4 Tandem Assembly for Photolytic Solar Fuels Production. J. Am. Chem. Soc. 2015, 137, 974-981. (15)Tan, Z. K.; Moghaddam, R. S.; Lai, M. L.; Docampo, P.; Higler, R.; Deschler, F.; Price, M.; Sadhanala, A.; Pazos, L. M.; Credgington, D.; et al. Bright Light-Emitting Diodes Based on Organometal Halide Perovskite. Nat. Nanotech. 2014, 9, 687-692. (16)Dou, L. T.; Yang, Y.; You, J. B.; Hong, Z. R.; Chang, W. H.; Li, G.; Yang, Y. Solution-Processed Hybrid Perovskite Photodetectors with High Detectivity. Nat. commun. 2014, 5: 5404.

22


Page 23 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(17)Xia, H. R.; Li, J.; Sun, W. T.; Peng, L. M. Organohalide Lead Perovskite Based Photodetectors with Much Enhanced Performance. Chem. Commun. 2014, 50(89): 13695-13697. (18)Lin, Q. Q.; Armin, A.; Lyons, D. M.; Burn, P. L.; Meredith, P. Low Noise, IR‐Blind Organohalide Perovskite Photodiodes for Visible Light Detection and Imaging. Adv. Mater. 2015, 27(12): 2060-2064. (19)Hao, F.; Stoumpos, C. C.; Cao, D. H.; Chang, R. P. H.; Kanatzidis, M. G. Lead-Free Solid-State Organic–Inorganic Halide Perovskite Solar Cells. Nat. Photon. 2014, 8(8): 489-494. (20)Iefanova, A.; Adhikari, N.; Dubey, A.; Khatiwada, D.; Qiao, Q. Q. Lead Free CH3NH3SnI3 Perovskite Thin-Film with P-Type Semiconducting Nature and Metal-Like Conductivity. Aip Adv. 2016, 6(8):6050. (21)Volonakis, G.; Filip, M. R.; Haghighirad, A. A.; Sakai, N.; Wenger, B.; Snaith, H. J.; Giustino, F. Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals. J. Phys. Chem. Lett. 2016, 7(7):1254-1259. (22)Savory, C. N.; Walsh, A.; Scanlon, D. O. Pb-Free Halide Double Perovskites Support High-Efficiency Solar Cells? Acs Energy Lett. 2016, 1(5): 949-955. (23)Zhao, X. G.; Yang, J. H.; Fu, Y. H.; Yang, D. W.; Xu, Q. L.; Yu, L. P.; Wei, S. H.; Zhang, L. J. Lead-Free Inorganic Halide Perovskites for Solar Cells via Cation-Transmutation. J. Am. Chem. Soc. 2017, 139(7): 2630-2638.

23



Page 24 of 28

(24)Slavney, A. H.; Hu, T.; Lindenberg, A. M.; Karunadasa, H. I. A Bismuth‐Halide Double Perovskite with Long Carrier Recombination Lifetime for Photovoltaic Applications. J. Am. Chem. Soc. 2016, 138(7): 2138-2141. (25)Liao, W. Q.; Zhao, D. W.; Yu, Y.; Grice, C. R.; Wang, C. L.; Cimaroli, A. J.; Schulz, P.; Meng, W. W.; Zhu, K.; Xiong, R. G.; et al. Lead‐Free Inverted Planar Formamidinium Tin Triiodide Perovskite Solar Cells Achieving Power Conversion Efficiencies up to 6.22%. Adv. Mater. 2016, 28(42): 9333-9340. (26)Qiu, X. F.; Jiang, Y. N.; Zhang, H. L.; Qiu, Z. W.; Yuan, S.; Wang, P.; Cao, B. Q. Lead‐Free Mesoscopic Cs2SnI6 Perovskite Solar Cells Using Different Nanostructured ZnO Nanorods as Electron Transport Layers. Phys. Status Solidi RRL 2016, 10(8): 587-591. (27)Marshall, K. P.; Walker, M.; Walton, R. I.; Hatton, R. A. Enhanced Stability and Efficiency in Hole-Transport-Layer-Free CsSnI3 Perovskite Photovoltaics. Nat. Energy 2016, 1(12): 16178. (28)Oku, T.; Ohishi, Y.; Suzuki, A.; Miyazawa, Y. Effects of Cl Addition to Sb-Doped Perovskite-Type CH3NH3PbI3 Photovoltaic Devices. Metals 2016, 6(7): 147. (29)Sun, P. P.; Li, Q. S.; Yang, L. N.; Li, Z. S. Theoretical Insights into A Potential Lead-Free Hybrid Perovskite: Substituting Pb2+ with Ge2+. Nanoscale 2016, 8(3): 1503-1512. (30)Gu, X. L.; Wang, Y. F.; Zhang, T.; Liu, D. T.; Zhang, R.; Zhang, P.; Wu, J.; Chen, Z. D.; Li, S. B. Enhanced Electronic Transport in Fe3+-doped TiO2 for

24


Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


High Efficiency Perovskite Solar Cells. J. Mater. Chem. C. 2017, 5(41): 10754-10760. (31)Cortecchia, D.; Dewi, H. A.; Yin, J.; Bruno, A.; Chen, S.; Baikie, T.; Boix, P. P.; Grätzel, M.; Mhaisalkar, S.; Soci, C.; et al. Lead-free MA2CuClxBr4–x Hybrid Perovskites. Inorg. chem. 2016, 55(3): 1044-1052. (32)Zhang, X. X.; Yin, J., Nie, Z. H.; Zhang, Q.; Sui, N.; Chen, B. L.; Zhang, Y. T.; Qu, K. G.; Zhao, J. S.; Zhou, H. W. Lead-Free and Amorphous Organic– Inorganic

Hybrid

Materials

for

Photovoltaic

Applications:

Mesoscopic

CH3NH3MnI3/TiO2 Heterojunction. RSC Adv. 2017, 7(59): 37419-37425. (33)Parobek, D.; Roman, B. J.; Dong, Y. T.; Jin, H.; Lee, E.; Sheldon, M.; Son, D. H. Exciton-to-Dopant Energy Transfer in Mn-Doped Cesium Lead Halide Perovskite Nanocrystals. Nano lett. 2016, 16(12): 7376-7380. (34)Liu, H. W.; Wu, Z. N.; Shao, J. R.; Yao, D.; Gao, H.; Liu, Y.; Yu, W. L.; Zhang, H.; Yang, B. CsPbxMn1–x Cl3 Perovskite Quantum Dots with High Mn Substitution Ratio. ACS nano, 2017, 11(2): 2239-2247. (35)Li, Y. L.; Sun, W. H.; Yan, W. B.; Ye, S. Y.; Rao, H. X.; Peng, H. T.; Zhao, Z. R.; Bian, Z, Q.; Liu, Z. W.; Zhou, H. P.; et al. 50% Sn‐Based Planar Perovskite Solar Cell with Power Conversion Efficiency up to 13.6%. Adv. Energy Mater. 2016, 6(24): 1601353. (36)Du, S. J.; Jing, L.; Cheng, X. H.; Yuan, Y.; Ding, J. X.; Zhou, T. L.; Zhan, X. Y.; Cui, H. Z. Incorporation of Cesium Ions into MA1–xCsxPbI3 Single Crystals:

25



Page 26 of 28

Crystal Growth, Enhancement of Stability and Optoelectronic Properties. J. phys. Chem. Let. 2018, 9: 5833-5839. (37)Stam, W. V.; Geuchies, J. J.; Altantzis, T.; Bos, K. H.; Meeldijk, J. D.; Aert, S. V.; Bals, S.; Vanmaekelbergh, D.; Donega, C. M. Highly Emissive Divalent-Ion-Doped Colloidal CsPb1–xMxBr3 Perovskite Nanocrystals through Cation Exchange. J. Am. Chem. Soc. 2017, 139(11): 4087-4097. (38)Zhou, Y.; Chen, J.; Bakr, O. M.; Sun, H. T. Metal-Doped Lead Halide Perovskites: Synthesis, Properties and Optoelectronic Applications. Chem. Mater. 2018, 30(19): 6589–6613. (39)Nayak, P. K.; Sendner, M.; Wenger, B.; Wang, Z. P.; Sharma, K.; Ramadan, A. J.; Lovrinčić, R.; Pucci, A.; Madhu, P. K.; Snaith, H. J. Impact of Bi3+ Heterovalent Doping in Organic–Inorganic Metal Halide Perovskite Crystals. J. Am. Chem. Soc. 2018, 140(2): 574-577. (40)Volonakis, G.; Filip, M. R.; Haghighirad, A. A.; Sakai, N.; Wenger, B.; Snaith, H. J.; Giustino, F. Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals. J. phys. Chem. lett. 2016, 7(7): 1254-1259. (41)Poindexter, J. R.; Jensen, M. A.; Morishige, A. E.; Looney, E. E.; Youssef, A.; Correa, J.; Wieghold, S.; Rose, V.; Lai, B.; Cai, Z. H.; et al. Distribution and Charge State of Iron Impurities in Intentionally Contaminated Lead Halide Perovskites. IEEE J. Photovolt. 2018, 8(1): 156-161. (42)Niu, G. D.; Guo, X. D.; Wang, L. D. Review of Recent Progress in Chemical Stability of Perovskite Solar Cells. J. Mater. Chem. A. 2014, 3(17):8970-8980. 26


Page 27 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(43)Davis, J. R.; Rohatgi, A.; Hopkins, R. H.; Blais, P. D.; Rai-Choudhury, P.; McCormick, J. R.; Molle, H. C. Impurities in Silicon Solar Cells. IEEE T. electron dev. 1980, 27(4): 677-687. (44)Coletti, G. Sensitivity of State-of-The-Art and High Efficiency Crystalline Silicon Solar Cells to Metal Impurities. Prog. Photovoltaics Res. & Appl. 2013, 21(5):1163-1170. (45)Collord, A. D.; Xin, H.; Hillhouse, H. W. Combinatorial Exploration of The Effects of Intrinsic and Extrinsic Defects in Cu2ZnSn(S,Se)4. IEEE J. Photovolt. 2017, 5(1): 288-298. (46)Cheng, X. H.; Jing, L.; Zhao, Y.; Du, S. J.; Ding, J. X.; Zhou, T. L. Crystal Orientation-Dependent Optoelectronic Properties of MAPbCl3 Single Crystals. J. Mater. Chem. C. 2018, 6(6): 1579-1586. (47)Ding, J. X.; Cheng, X. H.; Jing, L.; Zhou, T. L.; Zhao, Y.; Du, S. J. Polarization-Dependent

Optoelectronic

Performances

in

Hybrid

Halide

Perovskite MAPbX3 (X= Br, Cl) Single-Crystal Photodetectors. ACS appl. mater. & inter. 2017, 10(1): 845-850. (48)Turkulets, Y.; Shalish, I. Franz-Keldysh Effect in Semiconductor Built-in Fields. J. Appl. Phys. 2018, 124(7): 075102.

27



Page 28 of 28

Table Of Contents

Heterovalent Fe2+ and Fe3+ can bring lattice expansion, extend optical absorption range and cause more point defects of perovskites.

28


Fe3+ Doped into MAPbCl3 Single Crystal: Impact on Crystal

Recommend Documents