真空熱アニーリングによる屋内ペロブスカイト太陽電池用の堅牢なペロブスカイト形成

Oct 14, 2023

Scientific Reports volume 13、記事番号: 10933 (2023) この記事を引用

2171 アクセス

19 オルトメトリック

メトリクスの詳細

ペロブスカイト材料は、次世代の太陽電池デバイスの魅力的な候補です。 電荷キャリアの寿命が長いため、メタルハライドペロブスカイトは、低照度での採取に適した候補であることが知られています。 屋内光の放射照度スペクトルに一致させるために、適切な含有量の臭化物と塩化物を含むトリプルカチオン ペロブスカイト材料 (FA0.45MA0.49Cs0.06Pb(I0.62Br0.32Cl0.06)3) を構成し、最適なバンド ギャップ (例) \(\sim\)1.80 eV。 屋内条件では光子束が少ないため、再結合を最小限に抑えることが非常に望ましいです。 この目標を達成するために、私たちは初めて、反溶媒の堆積と真空熱アニール、つまり VTA の併用を組み合わせて、高品質のペロブスカイト膜を作製しました。 VTA は、励起子損失の主な原因である表面と粒界のトラップ状態を抑制しながら、コンパクトで緻密で硬い形態をもたらします。 低コストのカーボン電極アーキテクチャを採用した VTA デバイスは、平均電力変換効率 (PCE) 27.7 ± 2.7%、ピーク PCE 32.0% (ショックレー クワイサー限界 50 ～ 60%)、平均開路電圧 (Voc) を示しました。 0.93 ± 0.02 V、ピーク Voc は 0.96 V で、対照および加熱前の真空処理の値よりも大幅に大きくなっています。

Energy demand has been dramatically increasing owing to population explosion and industrial expansion. Metal-halide perovskite-based materials are fascinating candidates for the next-generation solar devices. Because of exceptional light to electricity conversion characteristic and rapid increase of PCE over time to more than 25%, they are extremely promising for future commercial applications with PCE rivaling those of silicon solar cells1,2. Furthermore, perovskite solar cells (PSCs) have good optoelectronic properties such as high absorption over the visible spectrum3, low exciton binding energies4, low non-radiative recombination rates5, long charge carrier diffusion lengths in the \(\mu\)m range, and tunable energy band gaps (Eg) from 1.47 to more than 3.06 eV6,7. Interestingly, fabrication processes of PSCs are facile and economical with low consumption of energy due to high solubility at temperatures less than 100 °C8,9. Perovskite materials can be deposited by using several approaches, such as spin coating, vapor assisted solution deposition, thermal vapor deposition, inkjet printing, slot-die coating, and spray coating10,11,12,13. However, spin-coating deposition is a simple method for laboratory scale perovskite fabrication. One-step spin coating is a technique where precursor solution is directly spin–coated onto substrates14,15. Using antisolvent in one–step deposition, repeated cation doping, or adding some additives could be used to obtain large grain size, along with uniform and dense perovskite films10,16. Interestingly, Eg of perovskite-based materials with ABX3 structure can be tuned by substitution engineering at any site (A, B, and/or X), which is an advantage of perovskite technology, enabling several applications such as light emitting diodes (LEDs), photodetectors (PDs), and solar cells for both outdoor and indoor conditions. Up until now, researchers have paid a lot of attention to photovoltaics for low light that can be applied to portable electronics and wireless telecommunication technologies because of the rise of Internet of Things (IoTs)17,18,19. Perovskite–based materials are widely tunable in terms of energy band gaps, allowing a variety of Eg values each for an optimal performance under a specific light condition20,21. As indoor light sources provide different spectrum outputs compared to those of sunlight; according to computational calculation21,22, the well-fit energy band gap for indoor applications ranges from 1.8 to 1.9 eV, which can be achieved by partial substitution of A-site with cesium (Cs), methylammonium (MA), and/or formamidinium (FA) and/or X-site via iodine (I), bromine (Br), and/or chlorine (Cl)22,23,24,25,26. Cheng, R. et al. reported energy band gap tuning by the introduction of Br and Cl into pristine MAPbI3 perovskite. The Eg can be enlarged from 1.61 to 1.80 eV (MAPbI2−xBrClx). Moreover, the addition of chlorine reduces trap-state density, halide migration, and non-radiative recombination while improving crystallization, resulting in high open circuit voltage (Voc) of 1.028 V and PCE of 36.2% under 1000 lux fluorescent light21. Cheng, R. et al. demonstrated that perovskite solar cell performance was improved, particularly for indoor light applications by chlorine additive. The chlorine doping contributes to higher extraction capability at the perovskite/hole transport layer interface, which is attributed to lower defects19. With proper addition of Br, the grain sizes of perovskite were enlarged, suppressing non-radiative recombination. Moreover, the stability was improved by the formation of a pseudo-cubic phase and PCE of 34.5% was realized 34 %) of perovskite photovoltaics with controlled bromine doping”. Nano Energy 75, 104984. https://doi.org/10.1016/j.nanoen.2020.104984 (2020)." href="/articles/s41598-023-37155-4#ref-CR27" id="ref-link-section-d5183487e721"27. Apart from the perovskite absorber layer, electron transport layer (ETL) also plays important roles. Ann, M. H. et al. reported that compact TiO2 (c-TiO2) layer was more efficient for indoor light applications than mesoporous TiO2 (m-TiO2) layer owing to the high density of interfacial traps from using m-TiO2, although m-TiO2 was better for one sun condition28. Dagar, J. et al. also reported tin oxide (SnO2) as the electron transport layer for perovskite solar cell tested under indoor illumination, showing PCE of 21.3% at 400 lux29. From previous studies, the trap states at the interfaces and/or the grain boundaries are the main sources of non-radiative recombination22,23,28. Especially for low light applications, trap-state density is of great importance as there are less photo-generated charges under indoor light environment. To circumvent this problem under one sun, researchers have paid attention to the application of vacuum treatment to boost nucleation during crystallization and remove residual solvents without using antisolvent30,31,32. Li, X. et al. applied vacuum treatment to fabricate FA0.81MA0.15PbI2.51Br0.45 in DMSO-GBL solvent system and put the wet film under a vacuum environment for a few seconds to promote DMSO-PbI1.7Br0.3-(FAI)0.85(MABr)0.1 intermediate phase by eliminating solvent. The intermediate phase could delay crystal growth, leading to larger grain size and a high PCE of 20.5% under one sun30. In another study, low band gap FA0.8MA0.2Sn0.5Pb0.5I3 was deposited by applying vacuum-assisted growth control (VAGC) instead of antisolvent technique; the wet spin-coated films were placed under vacuum at 10 Pa for 10 s and further annealed under N2 atmosphere, resulting in smooth surfaces, no pin holes, large columnar grain orientations, fast transportation of charge carriers, and improved charge-carrier lifetime32. Zhang, J. et al. fabricated quasi-2D PEA2MAn-1PbnI3n+1 film by spin coating and vacuum treatment of the wet film to create uniform dispersion of different-n-value nanoplates to boost nucleations and limit the grain sizes by fast evaporation of residual solvents. The vacuum-treated films exhibited high fill factor (FF) of 82.4% and PCE of 18.04%31. Bi, D. et al. reported that perovskite solution (FA0.9Cs0.1PbI3) was added with molecular modulators (S, N, and SN) and fabricated by the one-step deposition method and then applied with a short vacuum treatment after spin coating to remove N, N-dimethylformamide (DMF) without using antisolvent to encourage fast crystallization of the intermediates. As a result, they achieved a PCE of over 20% with an active area of 1 cm233. Vacuum treatment was also applied to two-step deposition during the perovskite formation when MAI was dropped onto a PbI2 film, resulting in rapid solvent removal and a supersaturated state where a tremendous amount of nuclei are formed and simultaneously grown under the competitive pressure from neighbor nuclei; as a result, compact and smooth perovskite films with high hardness and thermal stability were produced34. Moreover, vacuum process can be applied during thermal annealing. Xie, F. X. et al. reported the CH3NH3PbI3 film fabricated by conducting vacuum treatment during thermal annealing to eliminate CH3NH3Cl (MACl), which is an unwanted byproduct of the reaction: 3CH3NH3I + PbCl2 \(\to\) CH3NH3PbI3 + 2CH3NH3Cl, yielding a high PCE of 14.5%35. Feng, J. et al. reported Cs0.15FA0.85PbI3 films fabricated under an all vacuum process. The PbI2, FAI, and CsI were separately evaporated layer-by-layer; all precursor layers react to form complete perovskite by annealing under vacuum environment. As a result, they obtained PCE of 21.32%36./p>

The XRD patterns of perovskite films fabricated with and without VTA are illustrated in Fig. 2A. We found full transformation into perovskite thin films since PbI2 and hexagonal non-perovskite phase (δ-phase) peak could not be detected36, 50%. RSC Adv. 9(18), 10148–10154. https://doi.org/10.1039/c9ra01625b (2019)." href="/articles/s41598-023-37155-4#ref-CR39" id="ref-link-section-d5183487e1204"39. The XRD peak of our samples located at 14.5° corresponds to the crystallographic plane of (100), which is cubic phase40. The peak positions of perovskite are shifted to higher 2\(\uptheta\) degrees compared with our reference, which is around 14.0°40. According to Bragg’s law,/p>

34 %) of perovskite photovoltaics with controlled bromine doping”. Nano Energy 75, 104984. https://doi.org/10.1016/j.nanoen.2020.104984 (2020)./p> 50%. RSC Adv. 9(18), 10148–10154. https://doi.org/10.1039/c9ra01625b (2019)./p>