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Öğe Cyclopentadithiophene-based hole-transporting material for highly stable perovskite solar cells with stabilized efficiencies approaching 21%(Amer Chemical Soc., 2020) Akın, Seçkin; Bauer, Michael; Uchida, Ryusuke; Arora, Neha; Jacopin, Gwenole; Liu, Yuhang; Hertel, DirkThere is an urge to develop new hole-transporting materials (HTMs) for perovskite solar cells (PSCs), which can yield comparable power conversion efficiencies (PCEs) yet mitigate the issue of stability associated with the state-of-the-art HTM Spiro-MeOTAD. Herein, we designed and prepared C-2v-symmetric spiro-configured HTM-1 comprising a central acridine-cyclopentadithiophene core unit flanked with triarylamine moieties. PSCs containing a 40 nm thin HTM-1 layer for hole extraction yielded a stabilized PCE approaching 21% under standard illumination. Owing to its higher hole mobility (mu(h)) at low electric field, an impressive short-circuit current density (J(SC)) of 24.7 mA cm(-2) and a high fill factor (FF) of 0.77 have been achieved. More importantly, HTM-1-based PSCs presented an excellent long-term operational stability under continuous illumination for 400 h and thermal stability at 80 degrees C, which can be ascribed to its high glass transition temperature of 168 degrees C and superior moisture tolerance. Arguably, the confluence of high performance and remarkable stability will lead to the development of technologically interesting new, stable, and efficient PSCs.Öğe Hydrothermally processed CuCrO2 nanoparticles as an inorganic hole transporting material for low-cost perovskite solar cells with superior stability(Royal Soc Chemistry, 2018) Akın, Seçkin; Liu, Yuhang; Dar, M. İbrahim; Zakeeruddin, Shaik M.; Gratzel, Michael; Turan, Servet; Sönmezoğlu, SavaşDespite the impressive photovoltaic performances of perovskite solar cells (PSCs) with a power conversion efficiency (PCE) beyond 22%, intensive studies are still required to overcome ongoing issues such as cost, stability, and hysteresis. Here, for the first time, we report a cesium-containing triple-cation mixed-halide perovskite solar cell (n-i-p structure) by using hydrothermally synthesized inorganic CuCrO2 (CCO) delafossite nanoparticles as a hole transporting material (HTM). After optimization of the concentration, a fully homogeneous and completely covered CCO layer that facilitates fast carrier extraction and collection was obtained on the surface of the perovskite. Our CCO-based cells achieved the best PCE of 16.7% (average 16.04 +/- 0.40) with negligible hysteresis. More importantly, it was found that our cells showed a significant improvement in stability in ambient air compared with Spiro-OMeTAD HTM-based cells. After 60 days of storage in air without encapsulation, PCE remained at similar to 83% of the initial value with the CCO-based cells, whereas it decreased to similar to 24% of the initial value with devices based on the Spiro-OMeTAD HTM. Furthermore, cost estimation results indicated that the current prospect of CCO has an affordable cost/device ratio (similar to 180-fold cheaper than Spiro-OMeTAD). This work not only reveals the importance of air-stable inorganic HTMs, but also provides a low-cost HTM for highly efficient and stable PSCs.Öğe Interface modification to achieve high-efficiency and stable perovskite solar cells(Elsevier B.V., 2022) Wu, Yinghui; Zhu, Hongwei; Yu, Binbin; Akın, Seçkin; Liu, Yuhang; Shen, Zhongjin; Pan, Linfeng; Cai, HouzhiThe organic–inorganic hybrid perovskite solar cells (PSCs) achieve relatively high power conversion efficiencies (PCEs) over the past few years. However, defects on the surface and at the grain boundaries of the perovskite active layers are critical factors in ensuing perovskite devices. It is still a huge challenge to imminent the commercial use of this technology by passivating the defects of perovskite materials and corresponding interfaces. Here, we employ the HBPC ((4′-pentyl-[1,1′-biphenyl]-4-yl)methanaminium iodide) interface passivation strategy to prepare high-quality perovskite surfaces, which can significantly improve the efficiency and stability of PSCs. As compared to control cell (20.0%), the HBPC-passivated perovskite device achieves a champion PCE of 22.07% with less hysteresis. The obtained results show that the presence of HBPC on the perovskite film can reduce the charge trap density and extend the carrier recombination life, thereby boosting the performance of perovskite devices, leading a great promise in the pursuit of high-efficiency and stable PSCs.Öğe Low-cost and highly efficient carbon-based perovskite solar cells exhibiting excellent long-term operational and uv stability(Wiley, 2019) Arora, Neha; Dar, M. İbrahim; Akın, Seçkin; Uchida, Ryusuke; Baumeler, Thomas; Liu, YuhangToday's perovskite solar cells (PSCs) mostly use components, such as organic hole conductors or noble metal back contacts, that are very expensive or cause degradation of their photovoltaic performance. For future large-scale deployment of PSCs, these components need to be replaced with cost-effective and robust ones that maintain high efficiency while ascertaining long-term operational stability. Here, a simple and low-cost PSC architecture employing dopant-free TiO2 and CuSCN as the electron and hole conductor, respectively, is introduced while a graphitic carbon layer deposited at room temperature serves as the back electrical contact. The resulting PSCs show efficiencies exceeding 18% under standard AM 1.5 solar illumination and retain approximate to 95% of their initial efficiencies for >2000 h at the maximum power point under full-sun illumination at 60 degrees C. In addition, the CuSCN/carbon-based PSCs exhibit remarkable stability under ultraviolet irradiance for >1000 h while under similar conditions, the standard spiro-MeOTAD/Au based devices degrade severely.Öğe Stabilization of highly efficient and stable phase-pure FAPbI(3)perovskite solar cells by molecularly tailored 2D-overlayers(Wiley, 2020) Liu, Yuhang; Akın, Seçkin; Hinderhofer, Alexander; Eickemeyer, Felix T.; Zhu, Hongwei; Seo, Ji-YounAs a result of their attractive optoelectronic properties, metal halide APbI(3)perovskites employing formamidinium (FA(+)) as the A cation are the focus of research. The superior chemical and thermal stability of FA(+)cations makes alpha-FAPbI(3)more suitable for solar-cell applications than methylammonium lead iodide (MAPbI(3)). However, its spontaneous conversion into the yellow non-perovskite phase (delta-FAPbI(3)) under ambient conditions poses a serious challenge for practical applications. Herein, we report on the stabilization of the desired alpha-FAPbI(3)perovskite phase by protecting it with a two-dimensional (2D) IBA(2)FAPb(2)I(7)(IBA=iso-butylammonium overlayer, formed via stepwise annealing. The alpha-FAPbI(3)/IBA(2)FAPb(2)I(7)based perovskite solar cell (PSC) reached a high power conversion efficiency (PCE) of close to 23 %. In addition, it showed excellent operational stability, retaining around 85 % of its initial efficiency under severe combined heat and light stress, that is, simultaneous exposure with maximum power tracking to full simulated sunlight at 80 degrees C over 500 h.Öğe Ultrahydrophobic 3D/2D fluoroarene bilayer-based water-resistant perovskite solar cells with efficiencies exceeding 22%(Amer Assoc Advancement Science, 2019) Liu, Yuhang; Akın, Seçkin; Pan, Linfeng; Uchida, Ryusuke; Arora, Neha; Milic, Jovana V.; Hinderhofer, AlexanderPreventing the degradation of metal perovskite solar cells (PSCs) by humid air poses a substantial challenge for their future deployment. We introduce here a two-dimensional (2D) A(2)PbI(4) perovskite layer using pentafluoro-phenylethylammonium (FEA) as a fluoroarene cation inserted between the 3D light-harvesting perovskite film and the hole-transporting material (HTM). The perfluorinated benzene moiety confers an ultrahydrophobic character to the spacer layer, protecting the perovskite light-harvesting material from ambient moisture while mitigating ionic diffusion in the device. Unsealed 3D/2D PSCs retain 90% of their efficiency during photovoltaic operation for 1000 hours in humid air under simulated sunlight. Remarkably, the 2D layer also enhances interfacial hole extraction, suppressing nonradiative carrier recombination and enabling a power conversion efficiency (PCE) > 22%, the highest reported for 3D/2D architectures. Our new approach provides water-and heat-resistant operationally stable PSCs with a record-level PCE.
