The 86th JSAP Autumn Meeting, 2025
Durability of perovskite solar cell is enhanced by unique methods

September 7 - 10, The 86th JSAP Autumn Meeting, 2025 was held in Toki Messe and other surrounding facilities. Hot topics of OLED, oxide-TFT, and perovskite solar cell are closed up.

Blue OLED is manufactured by use of Al complex doped TADF

As concerns OLED, Yamagata University reported solution-processed Blue OLED using Al complex doped thermally activated delayed fluorescence (TADF).

Fig.1 Molecule structure of AlB-11)

Fig.2 Absorption and PL spectrum of solution, doped film1)

Figure 1 shows molecular structure of Al complex doped TADF "AlB-1", which was originally developed. Its film was manufactured by doping of carbazole derivative host material "26DCzPPy" at 10 wt%.

In estimate of thermal property, high heat resistance same as 498℃ (at 5% decomposition temperature) was obtained. Furthermore, in optical property of toluene liquid inclusive of TADF, photoluminescence quantum yield (PLQY) and emission peak wavelength were 42% and 452 nm respectively. And also, as result of optical property of above dopant and host mix film, as figure 2, PLQY and emission peak wavelength were 100% and 476 nm respectively.

The next, ITO anode/PEDOT:PSS hole injection layer/emission layer/electron transport layer/cathode device was pilot-produced by solution process mainly. Its emission peak wavelength was 475 nm, and also, high external quantum efficiency (EQE) same as 17.9% was obtained, too.

Integrate OLED, organic film solar cell, and organic-TFT

On the other hand, Suwa University of Science proposed a multifunctional device of OLED, organic film solar cell, and organic-TFT. In this device, it's possible to drive display and photo reflector by solar power, which is generated at daytime.

Fig.3 Device structure of multifunctional organic semiconductor device.2)

Figure 3 shows structure of pilot-produced device. In short, its structure is same as that of vertical type static induction transistor (SIT).

Firstly, PEDOT:PSS film was coated on glass substrate with ITO film, and then, rubren and EH44 were deposited by co-evaporation. The next, Al was deposited from opening area (20 μm width) of metal mask, and then, rubren and EH44 were deposited by co-evaporation again. Subsequently, p-Pyrrd-Phen and Al wee deposited as electron injection material and cathode by evaporation method. In evaporation process of Al gate, spacer was set between substrate and metal mask due to control of current.

Figure 4 shows device characteristics of multifunctional organic semiconductor device. As (a), in case of spacer-free, highest brightness same as 300 cd/m² was obtained. This means that it can be useful for display. As (b), in spite of very low power conversion efficiency (PCE) same as 0.024%, photovoltaic performance was confirmed surely. Furthermore, as (c), source-drain current could be controlled by gate voltage.

Fig.4 Device characteristics of multifunctional organic semiconductor device. 　(a) L-V characteristics of devices. (b) J-V characteristics. (c) IDS-VDS characteristics2)

If anneal temperature is high same as 500℃, characteristics of IGO-TFT is greatly improved

As regards oxide-TFT, the research group of Osaka Institute of Technology and Ushio announced influence of Ga doping amount and anneal temperature against device characteristics in manufacturing process of Ga doped InGaO(IGO)-TFT by the poster report.
In this experiment, a precursor In2O3 liquid was prepared by dissolved In(NO3)3･3H2O into ultra-pure water. And also, a precursor liquid was prepared by mix of In(NO3)3･3H2O and Ga(NO3)3･xH2O. These precursors were spin-coated on glass substrate with hydrophilic surface. After coating, it's irradiated by excimer light, and then, annealed at 300℃ or 500℃.

Fig.6 Microphotograph of a TFT (a) and Transfer characteristics for TFTs (b).3)

Fig.5 GI-XRD measurement results.3)

Figure 5 shows GI-XRD measurement results. Annealed In2O3 film at 300℃ was poly-crystal, on the other hand, IGO film was amorphous at 500℃ even. This is reason why crystal growth is suppressed by occurrence of distorted grating because of displaced Ga to In site.

Figure 6 shows transfer characteristics of top-gate top contact type In2O3-TFT and IGO-TFT. ON/OFF current ratio of annealed InO-TFT at 300℃ was 1.9×10⁵. In short, it's operated at clear switching. On the other hand, IGO-TFT was not operated as TFT. However, ON/OFF current ratio and carrier mobility of annealed IGO-TFT at 500℃ were 2.0×10⁷ and 70cm²/V･s respectively. Furthermore, drain current density was 10μA/μm, and also, hysteresis was decreased, too. This is reason why balance of carrier density and durability is enhanced because of suppression of oxygen defect by high oxygen affinity of Ga.

PCE of perovskite solar cell is improved by doping chelated compound into hole transport material

Saitama University reported that bottom of perovskite layer was passivated by doping chelated compound into hole transport material, as a result, power conversion efficiency (PCE) was increased.

Fig.7 Photo luminescence spectra4)

In the experiment, chelated compound such as BCP, BPhen, and, NBPhen were doped into chlorobenzene solvent at 0.11mM. PATT hole transport material and above solvents were coated on glass substrate (ITO/PFN/SnO2/perovskite layer).

Figure 7 shows photo luminescence spectra. In case of using BCP and BPhen, PL intensity was higher than that of reference (chlorobenzene only). This means that passivation of perovskite was mainly caused by BCP or BPhen.

Estimate result of device characteristics, PCE of BCP device and Bphen device were higher than that of reference device, particularly PCE of the former was 14%. Furthermore, in case of using a general hole transport material Spiro-OMeTAD, PCE of reference was 13.7%, on the other hand, that of BCP device was 18%. These results mean Voc and FF are increased by passivation of perovskite layer.

After coating Sn perovskite, films coverage is increased by vacuum quenching method

With respect to Sn series perovskite solar cell, Kyoto University reported a new process of Sn perovskite film, in order to deposit uniformly on large substrate.

As you know, the anti-solvent method is mainly used as coating method of perovskite film. In this process, anti-solvent is dropped in spin-coating process, as a result, perovskite crystal is rapidly grown. However, it's difficult to correspond with large substrate because of low coverage ratio against under layer. In fact, reported largest size is mere 1×1cm². For this reason, the research group developed anti-solvent free process by control of crystal grow using coordinating addition agent. Concretely, a precursor liquid is coated by various methods, and then, dried in vacuum environment, finally, annealed at 100℃ for 20 min.

Fig.8 J-V curves of Sn-PVK cell using MeO-2PACz (left) and Sn-PVK cell module (right)5)

In this research, vinylimidazole was selected as a coordinating addition agent because of high coordination force against Sn^2＋ ion. In case of coating Sn perovskite precursor without addition agent, coverage of perovskite film was 45%, on the other hand, in case of doping vinylimidazole, it's increased to 100%. Flat film inclusive of vinylimidazole and Sn ion was formed by vacuum quenching process, and then, annealed, as a result, dense Sn perovskite film was formed by elimination of vinylimidazole. While different hole transport materials (PEDOT/PSS, MeO-2PACz, and 2PACz) were used, thick uniformity of perovskite films was almost same. In case of using vinylimidazole, film uniformity was not influenced by surface property of under layer.

In a word, it's possible to form dense Sn perovskite film on hydrophobic hole transport layer, for example, MeO-2PACz. As figure 8-left, in pilot-produced device (ITO/MeO-2PACz/EDA0.01FA0.98SnI3/C60/BCP/Ag), relatively high PCE same as 11.6% was obtained. On the other hand, PCE of reference device using PEDOT/PSS was 10.5%. Furthermore, PCE of large module (7.5 ×7.5 cm²) was 6.8%. In short, this method was confirmed to be effective for large substrate.

C60 is best suited for ETL of inverted type perovskite device because of high penetration inside PVK

The research group of Chiba University and Nissan Chemical reported advantage of C60 as electron transport layer of inverted type perovskite solar cell was solved. If electron transport materials with electron affinity 3.7-4.2eV are used, electron level contact with perovskite is expected to be superior in principle. However, except for fullerene derivative such as C60, high PCE was not obtained in fact. For this reason, the research group compared C60 (4.0eV) and typical organic semiconductor "PT-CDA" (4.2eV). By the way, past reported PCE of C60 device and PT-CDA device were 25% and 14.3%.

Fig.10 Energy level diagrams at the interface of (a) C60/MAPbI3, (b) PTCDA/MAPbI3.6)

Fig9 Time evolution of MAES spectra of (a) C60 10 nm/MAPbI3, (b) PTCDA 10 nm/MAPbI3.6)

As the past research, C60 penetrates into perovskite layer CH3NH3PbI3 (MAPbI3), and then, covers defects in perovskite layer, as a result, PCE was increased by decrease of hysteresis. In this time, C60 film and PTCDA film were deposited at 10nm thickness by evaporation method.

As figure 9, MAES spectra of C60 was decreased with time, and then, it disappeared almost after 24h. On the other hand, that of PT-CDA remained after 168h even. In short, the both penetrate into perovskite layer, but C60 penetrates deeper than PT-CDA. As a result, C60 is best suited for electron transport material because of high penetration into perovskite layer.

H2O molecule is selectively trapped by direct insert of zeolite nanoparticle

The research group of University of Tokyo proposed to insert zeolite nanoparticle in device directly, in order to trap H2O molecule selectively and speedily as enhancement method of durability, which was most problem for practical use.

Fig.11 PCE evolution under 25℃, 90% RH conditions7)

In this experiment, a general perovskite solar cell (FTO/TiO2 layer/FAPbI3/Spiro-OMeTAD/Au) was pilot-produced. After surface modification of perovskite film by use of TMPS, ethanol solution inclusive of zeolite nanoparticle (diameter 50 nm) was spin-coated on FAPbI3 layer, and then, annealed at 150℃.

In case of surface modification-free, there were large aggregates same as 1μm on perovskite film, on the other hand, in case of surface modification, zeolite nanoparticle were uniformly dispersed on perovskite film.

PCE of device with zeolite nanoparticle were 19.7% almost same as that (20%) of reference device (wihtout). And also, figure 11, durability of the former was enhanced than that of the latter in durability test at 25℃ and 90%RH. In short, it's possible to suppress degradation of perovskite layer by use of zeolite nanoparticle.

Perovskite solar cell is encapsulated by laser irradiation of glass frit

On the other hand, National Institute of Advanced Industrial Science and Technology (AIST) reported proposed laser encapsulation method using glass frit as encapsulation method of perovskite solar cell.

Firstly, a glass paste is printed on the cover glass at line width=350 μm, film thickness=20 μm by the screen printing method, and then, pre-annealed at 400℃. After assembled cover glass and perovskite cell in N2 environment, it's irradiated in seal area only by IR laser (λ=940nm), as a result, assembled substrates are encapsulated by melted glass paste. After encapsulation, line width and film thickness of seal part was 410 μm, and 7 μm respectively. In short, glass frit was crushed by laser irradiation. Of course, it's possible to ensure high airtightness by melting of glass frit, and also, suppress temperature increase in device area because of local anneal by laser irradiation. By the way, distance of seal part and device area is mere 1 mm and over.

Fig.12 J-V curves of laser-assisted glass frit encapsulated perovskite solar cells.8)

Result of He leak test of an encapsulated dummy cell, He leak amount was mere 1.8×10⁸Pa･m³/sec. In a word, high airtightness of glass encapsulation was surely confirmed.

The next, the inverted type device (1.04 cm²) was pilot-produced, and then, encapsulated by this process. As figure 12, relatively high PCE same as 19.45% was obtained. In short, perovskite device is not damaged by this process.

Furthermore, result of durability test, initial property at 22℃ was not almost changed after 24h, on the other hand, that at 84℃ was decreased to 80% after 24h.

Pb, In, and Au are recovered from scrapped perovskite solar cell

Kanazawa University succeeded to recover and separate Au, In, and Pb from scrapped perovskite solar cell.

Fig.13 Recovery flow of perovskite solar cell9)

In this experiment, encapsulated perovskite solar cell (plastic substrate) was cut, and then, inclusion metals were resolved by anneal and agitation in mix of hydrochloric acid and nitric acid. The next, Au was recovered by agitation in above liquid and dithiocarbamate cellulose adsorbent (DMC-2). Subsequently, Pb and In were adsorbed by use of chelated resin, and then, separated by use of sulfuric acid.

As a result, Au could be selectively recovered at recovery ratio 85% and over. Furthermore, Pb was recovered from liquid to solid at recovery ratio 100%.


Reference
1)Chiba, et.al.：A blue aluminum complex exhibiting TADF for solution-processed OLED, The 86th JSAP Autumn Meeting, 2025, 12-025 (2025.9)
2)Tanahashi, et.al.：Fabrication and characterization of multifunctional organic semiconductor devices, The 86th JSAP Autumn Meeting, 2025, 12-030 (2025.9)
3)Ochiai, et.al.：Fabrication and characterization of top-gate InGaO thin-film transistors using aqueous precursor solutions with an excimer light irradiation processing, The 86th JSAP Autumn Meeting, 2025, 21-071 (2025.9)
4)Sasamoto, et.al.：Chelating hole-transport layers for efficient perovskite solar cells, The 86th JSAP Autumn Meeting, 2025, 12-378 (2025.9)
5)Harada, et.al.：Scalable and Substrate-independent Fabrication Method for Tin Perovskite Films by Vacuum Quenching, The 86th JSAP Autumn Meeting, 2025, 12-043 (2025.9)
6)Tosaki, et.al.：Uncovering the Origin of Fullerenes Superiority as Electron Transport Layers in Perovskite Solar Cells, The 86th JSAP Autumn Meeting, 2025, 12-045 (2025.9)
7)Koseki, et.al.：Durability Improvement of Perovskite Solar Cells Using Zeolite Nanoparticles under Humid Condition, The 86th JSAP Autumn Meeting, 2025, 12-442 (2025.9)
8)Araki, et.al.：Laser-assisted glass frit encapsulation of perovskite solar cells, The 86th JSAP Autumn Meeting, 2025, 12-401 (2025.9)
9)Yazawa, et.al.：Recovery of Lead and Metals from Perovskite Solar Cells Through Acid Dissolution and Selective Adsorbents, The 86th JSAP Autumn Meeting, 2025, 12-049 (2025.9)