Impact of Compact TiO2 Interface Modification on the Crystallinity of Perovskite Solar Cells

doi:10.21203/rs.3.rs-3012375/v1

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Impact of Compact TiO2 Interface Modification on the Crystallinity of Perovskite Solar Cells

https://doi.org/10.21203/rs.3.rs-3012375/v1

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published 26 Sep, 2023

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The effect of TiO2 interfacial morphology on perovskite crystallinity was investigated by modifying the micro and nanoscale surface roughness of compact TiO2. The surface treatment of compact TiO2 layer is considered as an effective strategy to improve a photovoltaic performance of perovskite solar cells although there is little discussion about the crystallinity of perovskite on top of TiO2. In this research, we have examined the impact of micro and nano scale surface roughness and its influence on perovskite crystal as well as the device performance. Surprisingly, while any noticeable voids were not observed at the interface between the compact TiO2 and perovskite layer, the morphology of the perovskite crystal showed a remarkable improvement by either the micro or nano scale interfacial modification and eventually resulted in an enhancement in photoconversion efficiency and I-V hysteresis. This result pointed out the importance of an underlayer surface morphology in perovskite crystallization process and the possibility that grain boundaries existing in perovskite layer may also be a factor affecting I-V hysteresis in perovskite solar cells.

Physical sciences/Chemistry/Energy

Physical sciences/Materials science/Materials for energy and catalysis/Solar cells

Organometal halide perovskite solar cell (PSC) has been attracting great attention due to its remarkable optoelectronic properties^1–5 available with a cost-effective fabrication process. PSC has achieved a drastic improvement in a photoconversion efficiency (PCE) since it was first reported in 2009⁶, that PCE now reaches over 25%, which is comparable to that of conventional crystalline silicon photovoltaics^7–10. Among the evolution of PSCs, a sequential structure, which a perovskite layer is deposited on top of an electron transport layer, is employed by a large number of highly efficient PSC devices and titanium oxide (TiO₂) is commonly used as an electron transport layer¹¹. However, it has been reported that an interface between TiO₂ and perovskite layers shows a mismatch in the junction since there is a large difference in a lattice constant between TiO₂ and that of perovskite¹². They also reported that I-V hysteresis, which PCE value differs depending on the scan direction, is caused by the electrostatic capacitance component generated by this mismatch of these interfaces^13,14 though it should be noted that an ionic migration of perovskite^15,16or a ferroelectric characteristic^17,18 of perovskite are also considered as possible origins of I-V hysteresis. At the same time, some paper has reported that PCE and I-V hysteresis improved by a surface treatment of the TiO₂ and perovskite interface^19,20. In these studies, they suggested that the surface treatment resulted in an improvement of a wettability of the TiO₂ surface and/or an adjustment of the valence band position of TiO₂, which thus led to an enhancement of the photo carriers generated in the perovskite layer transfer to the TiO₂ layer. On the other hand, there has been few discussions on deposited perovskite crystal itself affected by the surface treatment in the studies. However, it has been well discussed in the field of heteroepitaxy method in which a crystal or thin film is grown on a substrate with a different lattice constant, that the quality of the deposited crystals changes significantly depending on a condition of the interface of the underlayer crystals as it can cause a formation of dislocations or defects^21,22. Although perovskite thin films in PSC devices are different from the heteroepitaxy method that perovskite films are mainly fabricated by a spin coating method and are basically a multi crystal while heteroepitaxy method mainly performed with a single crystal, not only the junction state but also the crystallinity of the grown perovskite layer may possibly change by an interface modification for TiO₂ and perovskite layers.

In this report, we examined the effect of enhancing the contact of TiO₂ and perovskite interface on the perovskite crystallinity and subsequently evaluated the solar cell device performance. First, we focused on micro-level roughness and attempted to improve the physical gaps between TiO₂ and perovskite layers by introducing a FTO substrate with a flatter surface morphology than the commonly used FTO substrate. Next, we attempted to eliminate gaps at the nanometer level by depositing a mesoporous layer of TiO₂ nanoparticles that serve as scaffolds for perovskite layers on top of a dense layer of TiO₂ and further improved the TiO₂ and perovskite contact. The morphology of the perovskite films exhibited a remarkable improvement by the surface modifications that the grain boundaries observed at the perovskite layer reduced significantly. Our study demonstrated that the surface modification of a perovskite underlayer gives a drastic impact on not only to the interfacial contact but also the perovskite morphology.

The modification of micro scale roughness on the c-TiO₂/perovskite interface

At first, we focused on a micro scale surface roughness of TiO₂ and perovskite interface and adopted a flat FTO substrate as a means of improving the interfacial contact of TiO₂ and perovskite layers as some studies have identified the presence of voids or gaps at the interface as a major issue that leads to poor PCE and stability of the device^12,19. FTO substrate is a common material used as a transparent conductive oxide electrode in PSC devices though its surface typically exhibits a rough surface morphology with a scale of 0.5 to 1.0 μm that can exacerbate the physical gap in the interface. On the other hand, a FTO substrate used in this study has a flatter surface morphology than that of the generally used FTO substrate (Supplementary Figure 1). Thus, an introduction of the flatter FTO substrate is expected to improve the planarity of the interface, thereby reducing the likelihood of voids generates.

PSC device with a planer hetero junction structure was fabricated on the FTO substrate with a different surface morphology and its effect on a perovskite crystal deposited above was examined. For brevity, FTO substrate generally used in PSC device is denoted as “Rough FTO” and FTO substrate with a flatter surface morphology is denoted as “Flat FTO” respectively. Fig. 1 shows cross-sectional scanning electron microscopy (SEM) images of PSC devices prepared with the two FTO substrates having a different surface roughness. Further SEM images showing a wider range of the devices are shown in Supporting Figure 2. According to the SEM observations, few difference was observed in a film thickness of deposited layers depending on their FTO surface textures. The compact TiO₂, perovskite (CH₃NH₃PbI₃, MAPbI₃), spiro-OMeTAD and Au back contact layer had an average thickness of 50 nm, 600 nm, 180 nm, and 80 nm respectively. Moreover, by focusing on the interface between the compact TiO₂ dense layer and the perovskite layer, neither of the device had any noticeable gaps or voids at the TiO₂ and perovskite interface, which had been proposed as a major concern by the previous studies^12,19. This may be due to the fast crystallization deposition, a perovskite fabrication process that drips the antisolvent during the spin coating process²³, that this antisolvent dripping and a following immediate annealing process will facilitate the rapid crystallization of perovskite crystals, which may eventually lead to a formation of a minute nano crystal and thus did not generate a gap between the compact TiO₂ and perovskite layer.

However, when focused on the perovskite layer itself on the other hand, there was a significant difference appeared at the crystal morphology depending on the surface roughness of their FTO substrate. The perovskite layer that was fabricated with the Rough FTO substrate exhibited large crystal grain boundaries toward different directions throughout the film with a grain size of 300 to 500 nm. Furthermore, since the compact TiO₂ layer was deposited along with the rough surface morphology of the FTO substrate, the TiO₂ layer with a thickness of maximum 50 nm seems to be heavily affected by the Rough FTO’s morphology. Consequently, crystal growth direction of the perovskite layer was also likely to be affected by the morphology, which is demonstrated in Fig.1(a). On the other hand, the compact TiO₂ layer deposited on the flat FTO had a flatter and more uniform surface in response to the morphology of the FTO substrate. Surprisingly, the perovskite layer fabricated with the Flat FTO substrate had much fewer grain boundaries than that of the perovskite layer with the Rough FTO. In addition, boundaries were generated more toward the vertical direction than the horizontal direction, which is apparent in Fig. 1(b).

Surface morphology of the perovskite films deposited on the underlayer with a different surface morphology was also examined by the top view SEM observation shown in Supporting Figure 3. Both perovskite films were uniformly covered with a grain size of around 100 to 500 nm without any notable pinholes regardless of the surface morphology of FTO substrates. Further examination by X-ray diffraction (XRD) measurement is also shown in Supporting Figure 4. The diffraction patterns confirmed that both perovskite films have a crystal structure of an unoriented tetragonal MAPbI₃ that is well consistent with the diffraction pattern shown by the previous report²⁴. Despite the basic composition and crystal structure did not exhibit any noticeable differences, their perovskite film quality seems to vary significantly depending on their underlayer’s morphology.

The substantial improvement derived by the surface modification was also examined by the current – voltage (I-V) measurement of the solar cell devices. I-V curves and each photovoltaic parameters of PSC devices fabricated with rough and flat FTO substrates are shown in Fig. 2 and Table 1. For the evaluation of I-V hysteresis, the hysteresis factors¹⁶, defined by Eq. (1) below for the perovskite solar cells was calculated.

$$Hysteresis factor=(PC{E}_{reverse} - PC{E}_{forward}) / PC{E}_{reverse} \cdots Eq.\left(1\right)$$

Despite both samples have the same device structure and material compositions, the introduction of flat FTO in PSC devices also showed a clear enhancement of the photovoltaic performances. The device with flat FTO exhibited an increase in V_oc and fill factor (FF), which resulted in an improvement of overall PCE. Moreover, despite the mismatch between compact TiO₂ and perovskite layer, that had been previously demonstrated as a potential cause of I-V

Table 1 Photovoltaic parameters of solar cells fabricated with rough FTO and flat FTO.

Sample	Scan direction	J_sc (mAcm^-2)	V_oc (V)	FF (-)	PCE (%)	Hysteresis factor (-)
Rough FTO	Fwd	20.9	0.94	0.30	6.0	0.41
Rough FTO	Rev	21.2	1.02	0.46	10.0	0.41
Flat FTO	Fwd	19.5	1.03	0.62	12.4	0.17
Flat FTO	Rev	19.5	1.08	0.72	15.1	0.17

hysteresis, was not observed in our devices, I-V hysteresis behavior also showed a difference by their FTO surface morphology. This result may be induced by the perovskite layer with diminished horizontal grain boundaries, which will facilitate a carrier transportation and eventually led to the better device performance. Indeed, grain boundaries existing in the crystal have been reported to hinder a carrier transport or cause an undesired recombination of carriers, which can eventually lower the photovoltaic performance. These undesirable characteristics have been reported not only for perovskite solar cells but also for multi crystalline silicon solar cells^25,26. deQuilettes and co-workers examined the effect of microstructure on carrier dynamics in perovskite thin films according to the photoluminescence spectroscopy ¹⁸. They reported that grain boundaries showed lower photoluminescence and exhibited a faster nonradiative decay compared with those of bulk perovskite crystals. There is also a report that a device with potassium doped perovskite could diminish the grain boundary of perovskite layer and achieved a hysteresis free photovoltaic performance^27,28. Their results are consistent with our suggestion that carrier recombination and/or internal resistance were successfully prevented by the elimination of grain boundaries, which may eventually lead to the improvement of solar cell performances. Our results also indicate that presence of grain boundaries in the perovskite crystal may also be a crucial factor that causes I-V hysteresis in PSC devices.

The modification of nano scale roughness on the c-TiO₂/perovskite interface

Secondly, based on the abovementioned results we further discuss the effect of TiO₂/perovskite interfacial contact on the deposited perovskite crystal by modifying a nano meter scale surface roughness. Herein, we fabricated a nanoparticle TiO₂ layer on top of the compact TiO₂ dense layer to create a mesoscopic structured PSC device, which has been reported to have a higher efficiency than the device with the planar heterojunction structure. Using two types of FTO substrates, Rough FTO and Flat FTO, a compact TiO₂ dense layer was deposited followed by a TiO₂ mesoporous layer. The deposition of the perovskite layer, the hole transport layer, and the gold electrode was carried out in the same manner as the process for the planer hetero junction structure.

Cross sectional SEM images of PSC devices fabricated with and without mesoporous TiO₂ layer are shown in Fig. 3 (SEM images showing a wider range of the mesoscopic structure device are also shown in Supporting Figure 2). Both devices had almost the same film thickness for the compact TiO₂, perovskite, Spiro-OMeTAD and Au electrode with a thickness of 50 nm, 600 nm, 180 nm, and 80 nm respectively. For the mesoscopic structure device, mesoporous TiO₂ layer was introduced on top of the compact TiO₂ layer with an average thickness of 100 nm. As with the result shown in Fig. 1, while the perovskite layer fabricated with the planer hetero junction structure exhibited the severe grain boundaries toward various directions, the perovskite film fabricated on the mesoporous TiO₂layer appeared with the much smoother surface as well as the much less grain boundaries that their horizontal direction almost disappeared. This feature is consistent with the result obtained in the SEM images of the planer hetero junction structure device fabricated with the flat FTO. This result demonstrates that the introduction of mesoporous TiO₂ layer induced the perovskite crystal to interlock with the pores of TiO₂ nanoparticles with filling the gap produced from the rough surface morphology of the FTO substrates. Therefore, the growth direction of the perovskite crystal was controlled, resulting in a dense film with significantly diminished grain boundaries. According to the top view SEM observation shown in Supporting Figure 3, the perovskite film was uniformly covered with a grain size around 100 to 500 nm and there was no apparent difference in the perovskite morphology compared with other perovskite films. Further examination by XRD measurement confirmed that the perovskite film fabricated on mesoporous TiO₂ layer is a tetragonal MAPbI₃ without any preferential orientations (Supporting Figure 4). While the device with rough FTO presented a considerable development by the application of mesoporous TiO₂, the device with flat FTO did not show such a notable difference in presence of mesoporous TiO₂ layer. However, as the Supporting Figure 5 shows, grain boundaries were effectively diminished, and the perovskite morphology improved slightly compared with the planer hetero junction device. It has been pointed out that among the papers achieving the highly efficient PSC devices, mesoscopic structure account for a large part of the reports and thus the investigations for the reason why mesoscopic structure affords superior performance may be a key for the further improvement of PSCs¹¹. They noted the effective electron extraction derived by a large area contact between the perovskite and TiO₂ layer as a possible advantage of mesoscopic structure, but our results also indicate another possible role of mesoscopic structure, which controls the crystal growth of perovskite leading to the formation of a higher quality film with less grain boundaries.

Table 2 Photovoltaic parameters of solar cells fabricated with planer and mesoscopic structure.

Sample	Scan direction	J_sc (mAcm^-2)	V_oc (V)	FF (-)	PCE (%)	Hysteresis factor (-)
Planer structure	Fwd	20.9	0.94	0.30	6.0	0.41
Planer structure	Rev	21.2	1.02	0.46	10.0	0.41
Mesoscopic structure	Fwd	23.9	1.04	0.59	14.6	0.19
Mesoscopic structure	Rev	23.9	1.08	0.70	18.0	0.19

Solar cell performance of the planer hetero junction and mesoscopic structured devices are summarized in Fig. 4 and Table 2. The device fabricated with Rough FTO which showed I-V hysteresis in planer hetero junction structure achieved a significant improvement by the introduction of the mesoporous TiO₂ layer that the PCE showed more than 1.5 times larger value than that of the planer structured devices. In addition, while the device with planer hetero junction structure showed a large hysteresis in I-V measurement, hysteresis factor decreased as half of the planer hetero junction structure’s value in mesoscopic structure devices.

On the other hand, the device with Flat FTO which showed the improvement of PCE and I-V hysteresis with the planer hetero junction structure did not show a notable improvement in I-V hysteresis, although the photovoltaic parameters and overall PCE improved by introducing a mesoporous TiO₂ layer (Supporting Figure 6). However, Rough FTO obtained a higher short-circuit current value than that of the Flat FTO, as shown in Table S1. This trend was also observed for the device in planer hetero junction structure as shown in Table 1. This may be due to the flat surface morphology that Flat FTO has, which reflects incident light and causes loss of absorbed light, while Rough FTO has a rough surface morphology that causes the reabsorption of reflected light and thus possible to absorb light more than the Flat FTO.

As confirmed by SEM observations, mesoscopic structure devices with both rough and flat FTO exhibited the improvement in perovskite morphology indicating the further efficacy of the surface treatment of TiO₂ layer on perovskite crystallization. In addition to the enhancement in the perovskite crystallinity, an increase in the coverage area of the perovskite layer by TiO₂ nanoparticles will lead to an efficient electron injection, which will be associated with the improved the photovoltaic characteristics of the mesoscopic structure devices. At the same time, since it is deposited with a thickness of around 100 nm, the TiO₂ nanoparticles eliminated the gaps between TiO₂ and perovskite layer within a nano meter scale, and therefore seems to obscure the impact of macro scale surface modification derived by the flat FTO.

In summary, we examined the effect of improving the interfacial contact of TiO₂/perovskite on the crystallinity of the fabricated perovskite layer as well as the subsequent photovoltaic characteristics of the solar cell devices. First, we introduced a FTO substrate with a smoother surface morphology as a method to eliminate the micro scale voids between TiO₂ and perovskite layers. Then a mesoporous TiO₂ layer was introduced for the further nano scale modification of TiO₂ and perovskite contact. SEM observation revealed that not only the interface between the TiO₂ and perovskite layers, but also the perovskite morphology showed a drastic improvement by the introduction of flat FTO substrate. Along with exploring the impact of surface treatment on the perovskite crystallinity, we also confirmed the improvement of PSC device photovoltaic characteristics as well as the I-V hysteresis. The observed enhancement is also confirmed by inducing the mesoporous TiO₂ layer that the presence of grain boundaries across the entire film resulted in a noticeable decrease with a conventional FTO substrate associated with the notable improvement of I-V hysteresis and photovoltaic characteristics. These results clearly demonstrated that the modification of compact TiO₂ and perovskite interface not only improves the contact, but also gives a significant impact on the crystal morphology of the perovskite layer. As the photovoltaic performance including I-V hysteresis changed in response to the perovskite morphology, the presence of grain boundaries inside perovskite layers is also likely to be responsible for the cause of I-V hysteresis. Our results emphasize the importance of underlying surface morphology on the resulting perovskite film quality, which will contribute to the further development of the perovskite crystallization process in future.

Materials.

All chemicals were stored in a drying room with a dew point temperature of –30℃ and employed without having any purification. As for the transparent conductive layer, fluorine doped tin oxide (FTO) substrates were purchased from Nippon Sheet Glass Co. Ltd (NSG) and SPD laboratory Inc (SPD). They are mentioned as “rough FTO” for the one from NSG and “flat FTO” for the one from SPD respectively. Both FTO substrates showed an average sheet resistance of 10 Ω/□ and 80% transmittance in visible range while an average film thickness was 800 nm for rough FTO and 1000 nm for flat FTO. The chemicals to prepare perovskite layer, PbI₂ (99.99%) is obtained from Kojundo Chemical Laboratory Co., LTD and MAI from Tokyo Chemical Industry (TCI). Titanium diisopropoxide bis (acetylacetonate) (75wt% in isopropanol), lithium bis (trifluoro methanesulfonyl) imide (LiTFSI) and 4-tert-butylpyridine (tBP) are purchased from Sigma-Aldrich. TiO₂ paste with a size of 24 nm nano particle was purchased from JGC C&C. Spiro-OMeTAD ((2,20,7,70-tetrakis-(N,N-di-4-methoxyphenylamino)-9,90-spirobifluorene)) is bought from Merck. All the solvents are obtained from Wako Pure Chemical Industries, LTD.

Device fabrication.

The basic device structure of fabricated PSC is FTO / compact TiO₂ / perovskite (MAPbI₃) / Spiro-OMeTAD / Au. For the device with mesoscopic structure, mesoporous TiO₂ was fabricated on the compact TiO₂ layer before the perovskite layer fabrication. All samples were fabricated on same date in the same batch. As for the transparent conductive layer, FTO glasses are cleaned by a sonication in acetone and ethanol for 10 min respectively. A compact TiO₂ layer was deposited on the cleaned FTO glass substrates by spray pyrolysis deposition with the solution of 300 µL titanium diisopropoxide bis (acetylacetonate), dispersed in 4.00 mL of ethanol. Then they were annealed at 430 °C for 15 min. For the device with the mesoscopic structure, a mesoporous TiO₂ layer was fabricated by spin coating 24 nm TiO₂ nano particles dispersed in ethanol with a rotation speed of 6000 rpm for 30 sec. Then the sample was annealed at 550℃ for 15 min. Then a perovskite absorber layer was deposited by the fast deposition-crystallization method. A perovskite precursor solution containing 1.4 M of PbI₂, and 1.4 M of MAI was prepared by dissolving all the powders in solvents mixing 632 µL of DMF and 71.0 µL of DMSO. After dropping the precursor solution, a two-step spin coating with a rotation speed of 1000 rpm for 10 sec and 5000 rpm for 40 sec was conducted to disperse the droplets. During the spin coating, 0.6 mL of chlorobenzene was quickly dropped 22 sec after the beginning of the program. The as-spun films were annealed at 70℃ for 1 min followed by the further anneal at 100℃ for 30 min. Then a hole transport layer was spin coated using a solution of Spiro-OMeTAD (72.3 mg/mL) in chlorobenzene (1.00 mL). To increase conductivity, LiTFSI (520 mg/mL in acetonitrile, 17.5 µL) and tBP (26.8 µL) were added to the solution. The solution was spin coated with a rotation speed of 4000 rpm for 30 sec and annealed for 10 min at 70℃. At last, Au electrode with the thickness of around 80 nm was deposited by a thermal evaporation, and the area of the Au contact was more than 0.18 cm². All processes were performed in the drying room and fabricated devices were stored in the dry room for a day before the measurements.

Device evaluation.

The current -voltage (I-V) curves were measured and recorded under AM 1.5G illumination (100 mW/cm²) with a 450 W xenon light source (YSS-80A; Yamashita Denso Co., Ltd., Japan). The light source was calibrated using a silicon photodiode of BS-520 (Bunkoukeiki Co., Ltd., Japan). Scan speed of the measurement was fixed as 100 mV/s. A black mask was used to confirm the photoactive area of 0.181 cm² during the measurements. Surface and cross section morphology was observed using a field emission scanning electron microscope (SEM, SU 8000, Hitachi). X-ray diffraction (XRD) measurement was carried out on a Bruker D8 Discover with Cu K-alpha radiation (λ = 0.15406 nm).

Data Availability

All data generated or analyzed during this study are included in this published article (and its Supplementary Information files).

Acknowledgements

This paper is based on results obtained from a project, JPNP21016, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Also, this work was supported by JST SPRING, Grant Number JPMJSP2108.

Author contributions

S.T., S.U. and H.S. developed the basic concept. S.T. did all the experiments including the fabrication and evaluation of the PSC devices. S.U. and H.S. provided technical advice regarding PSCs. P.J. and S.K. supplied flat FTO. S.T., S.U., and H.S. analyzed the data and S.T prepared all the figures in this paper. S.T wrote the main manuscript test. All authors discussed the results and revised the paper. H.S. directed the project.

Additional Information

The authors declare no competing financial and non-financial interests.

Green, M. A., Ho-Baillie, A. & Snaith, H. J. The emergence of perovskite solar cells. Nat Photonics 8, 506–514 (2014).
Stranks, S. D. et al. Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber. Science (1979) 342, 341–344 (2013).
Dong, Q. et al. Electron-hole diffusion lengths > 175 m m in solution-grown CH 3 NH 3 PbI 3 single crystals. Science (1979) 347, 967–970 (2015).
Giorgi, G., Fujisawa, J. I., Segawa, H. & Yamashita, K. Small photocarrier effective masses featuring ambipolar transport in methylammonium lead iodide perovskite: A density functional analysis. Journal of Physical Chemistry Letters 4, 4213–4216 (2013).
Yin, W. J., Shi, T. & Yan, Y. Superior photovoltaic properties of lead halide perovskites: Insights from first-principles theory. Journal of Physical Chemistry C 119, 5253–5264 (2015).
Kojima, A., Teshima, K., Shirai, Y. & Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J Am Chem Soc 131, 6050–6051 (2009).
(NREL)The National Renewable Energy Laboratory. Best-Research-Cell-Efficiencies-Rev210726.pdf. https://www.nrel.gov/pv/cell-efficiency.html.
Kim, G. et al. Impact of strain relaxation on performance of a-formamidinium lead iodide perovskite solar cells. Science (1979) 370, 108–112 (2020).
Yoo, J. J. et al. Efficient perovskite solar cells via improved carrier management. Nature 590, 587–593 (2021).
Jeong, J. et al. Pseudo-halide anion engineering for α-FAPbI3 perovskite solar cells. Nature 592, 381–385 (2021).
Nakazaki, J. & Segawa, H. Evolution of organometal halide solar cells. Journal of Photochemistry and Photobiology C: Photochemistry Reviews 35, 74–107 (2018).
Cojocaru, L. et al. Temperature effects on the photovoltaic performance of planar structure perovskite solar cells. Chem Lett 44, 1557–1559 (2015).
Cojocaru, L. et al. Origin of the Hysteresis in I – V Curves for Planar Structure Perovskite Solar Cells Rationalized with a Surface Boundary-induced Capacitance Model. Chem Lett 44, 1750–1752 (2015).
Cojocaru, L. et al. Simulation of current-voltage curves for inverted planar structure perovskite solar cells using equivalent circuit model with inductance. Applied Physics Express 10, 4–7 (2017).
Eames, C. et al. Ionic transport in hybrid lead iodide perovskite solar cells. Nat Commun 6, 2–9 (2015).
Calado, P. et al. Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresis. Nat Commun 7, 1–10 (2016).
Frost, J. M. et al. Atomistic origins of high-performance in hybrid halide perovskite solar cells. Nano Lett 14, 2584–2590 (2014).
Chen, H. W., Sakai, N., Ikegami, M. & Miyasaka, T. Emergence of hysteresis and transient ferroelectric response in organo-lead halide perovskite solar cells. Journal of Physical Chemistry Letters 6, 164–169 (2015).
Cojocaru, L. et al. Surface treatment of the compact TiO2 layer for efficient planar heterojunction perovskite solar cells. Chem Lett 44, 674–676 (2015).
Murakami, T. N. et al. Adjustment of Conduction Band Edge of Compact TiO2 Layer in Perovskite Solar Cells Through TiCl4 Treatment. ACS Appl Mater Interfaces 9, 36708–36714 (2017).
Wu, P. et al. Lattice mismatch induced nonlinear growth of graphene. J Am Chem Soc 134, 6045–6051 (2012).
Kinjo, R., Kawayama, I., Murakami, H. & Tonouchi, M. Thickness Dependence of Dielectric Characteristics of SrTiO 3 Thin Films on MgAl 2 O 4 Substrates. Advances in Materials Physics and Chemistry 2013, 58–61 (2013).
Xiao, M. et al. A Fast Deposition-Crystallization Procedure for Highly Efficient Lead Iodide Perovskite Thin-Film Solar Cells. Angewandte Chemie 126, 10056–10061 (2014).
Stoumpos, C. C., Malliakas, C. D. & Kanatzidis, M. G. Semiconducting tin and lead iodide perovskites with organic cations: Phase transitions, high mobilities, and near-infrared photoluminescent properties. Inorg Chem 52, 9019–9038 (2013).
Grovenor, C. R. M. M. Grain boundaries in semiconductors. Journal of Physics C: Solid State Physics 18, 4079–4119 (1985).
Long, R., Liu, J. & Prezhdo, O. V. Unravelling the Effects of Grain Boundary and Chemical Doping on Electron-Hole Recombination in CH3NH3PbI3 Perovskite by Time-Domain Atomistic Simulation. J Am Chem Soc 138, 3884–3890 (2016).
Tang, Z. et al. Hysteresis-free perovskite solar cells made of potassium-doped organometal halide perovskite. Sci Rep 7, 1–7 (2017).
Tang, Z. et al. Modulations of various alkali metal cations on organometal halide perovskites and their influence on photovoltaic performance. Nano Energy 45, 184–192 (2018).

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