Orbital Interactions in 2D Dion-Jacobson Perovskites Using Oligothiophene-Based Semiconductor Spacers Enable Efficient Solar Cells.

2D Dion-Jacobson (DJ) perovskites have emerged as promising photovoltaic materials, but the insulating organic spacer has hindered the efficient charge transport. Herein, we successfully synthesized a terthiophene-based semiconductor spacer, namely, 3ThDMA, for 2D DJ perovskite. An interesting finding is that the energy levels of 3ThDMA extensively overlap with the inorganic components and directly contribute to the band formation of (3ThDMA)PbI4, leading to enhanced charge transport across the organic spacer layers, whereas no such orbital interactions were found in (UDA)PbI4, a DJ perovskite based on 1,11-undecanediaminum (UDA). The devices based on (3ThDMA)MAn-1PbnI3n+1 (nominal n = 5) obtained a champion efficiency of 15.25%, which is a record efficiency for 2D DJ perovskite solar cells using long-conjugated spacers (conjugated rings ≥ 3) and a 22.60% efficiency for 3ThDMA-treated 3D PSCs. Our findings provide an important insight into understanding the orbital interactions in 2D DJ perovskite using an organic semiconductor spacer for efficient solar cells.

Multiarmed Aromatic Ammonium Salts Boost the Efficiency and Stability of Inverted Organic Solar Cells.

Inverted organic solar cells (OSCs) have attracted much attention because of their outstanding stability, with zinc oxide (ZnO) being commonly used as the electron transport layer (ETL). However, both surface defects and the photocatalytic effect of ZnO could lead to serious photodegradation of acceptor materials. This, in turn, hampers the improvement of the efficiency and stability in OSCs. Herein, we developed a multiarmed aromatic ammonium salt, namely, benzene-1,3,5-triyltrimethanaminium bromide (PhTMABr), for modifying ZnO. This compound possesses mild weak acidity aimed at removing the residual amines present within ZnO film. In addition, the PhTMABr could also passivate surface defects of ZnO through multiple hydrogen-bonding interactions between its terminal amino groups and the oxygen anion of ZnO, leading to a better interface contact, which effectively enhances charge transport. As a result, an efficiency of 18.75% was achieved based on the modified ETL compared to the bare ZnO (PCE = 17.34%). The devices utilizing the modified ZnO retained 87% and 90% of their initial PCE after thermal stress aging at 65 °C for 1500 h and continuous 1-sun illumination with maximum power point (MPP) tracking for 1780 h, respectively. Importantly, the extrapolated T80 lifetime with MPP tracking exceeds 10 000 h. The new class of materials employed in this work to modify the ZnO ETL should pave the way for enhancing the efficiency and stability of OSCs, potentially advancing their commercialization process.

Inverted Wide-Bandgap 2D/3D Perovskite Solar Cells with >22% Efficiency and Low Voltage Loss.

Wide-bandgap perovskites play a key role in high-performance tandem solar cells, which have the potential to break the Schockley-Queisser limit. Here, a 2D/3D hybrid wide-bandgap perovskite was developed using octane-1,8-diaminium (ODA) as spacer. The incorporation of the ODA spacer can not only significantly reduce charge carrier nonradiative recombination loss but also inhibit phase separation. Moreover, with a synergy effect using butylammonium iodide (BAI) as a surface defect passivator, both the phase stability and device performance were further improved. Compared to the control inverted device with a VOC of 1.16 V and a PCE of 18.50%, the optimized PSCs based on a surface processed 2D/3D perovskite exhibit a superior high VOC of 1.26 V and a champion PCE of 22.19%, which is a record efficiency for wide-bandgap PSCs (Eg > 1.65 eV). This work provides a very effective strategy to suppress phase separation in wide-bandgap perovskites for highly efficient and stable solar cells.

Crystal Growth Regulation of Ruddlesden-Popper Perovskites via Self-Assembly of Semiconductor Spacers for Efficient Solar Cells.

The crystal growth and orientation of two-dimensional (2D) perovskite films significantly impact solar cell performance. Here, we incorporated robust quadrupole-quadrupole interactions to govern the crystal growth of 2D Ruddlesden-Popper (RP) perovskites. This was achieved through the development of two unique semiconductor spacers, namely PTMA and 5FPTMA, with different dipole moments. The ((5FPTMA)0.1 (PTMA)0.9 )2 MAn-1 Pbn I3n+1 (nominal n=5, 5F/PTMA-Pb) film shows a preferred vertical orientation, reduced grain boundaries, and released residual strain compared to (PTMA)2 MAn-1 Pbn I3n+1 (nominal n=5, PTMA-Pb), resulting in a decreased exciton binding energy and reduced electron-phonon coupling coefficients. In contrast to PTMA-Pb device with an efficiency of 15.66 %, the 5F/PTMA-Pb device achieved a champion efficiency of 18.56 %, making it among the best efficiency for 2D RP perovskite solar cells employing an MA-based semiconductor spacer. This work offers significant insights into comprehending the crystal growth process of 2D RP perovskite films through the utilization of quadrupole-quadrupole interactions between semiconductor spacers.

CsPbI3-Based Phase-Stable 2D Ruddlesden-Popper Perovskites for Efficient Solar Cells.

Inorganic CsPbI3 perovskite has shown great promise in highly stable perovskite solar cells due to the lack of volatile organic components. However, the inferior phase stability in ambient conditions resulted from the very small Cs+, limiting their practical applications. Here, CsPbI3-based 2D Ruddlesden-Popper (RP) perovskites were developed using two thiophene-based aromatic spacers, namely, 2-thiophenemethylamine hydroiodide (ThMA) and 2-thiopheneformamidine hydroiodide (ThFA), which significantly improved the phase stability by releasing the large inner stress of black-phase CsPbI3. The optimized ThFA-based 2D RP perovskite (n = 5, ThFA-Cs) device achieves a record efficiency of 16.00%. Importantly, the ThFA-Cs devices could maintain an average of 98% of their initial efficiencies after being stored in N2 at room temperature for 3000 h and 92% of their initial value at 80 °C for 960 h. This work provides a new perspective for exploration of the phase-stable CsPbI3-based perovskite with reduced dimensions for high-performance solar cells.

Nucleation and Crystallization in 2D Ruddlesden-Popper Perovskites using Formamidinium-based Organic Semiconductor Spacers for Efficient Solar Cells.

The conjugated organic semiconductor spacers have drawn wide attention in two-dimensional (2D) perovskites and formamidinium (FA) has been widely used as A-site cation in high-performance 3D perovskite solar cells (PSCs). However, the FA-based semiconductor spacers have rarely been investigated in 2D Ruddlesden-Popper (RP) perovskites. Here, we developed two FA-based spacers containing thieno[3,2-b]thiophene (TT) and 2,2'-bithiophene (BT) units, namely TTFA and BTFA, respectively, for 2D RP PSCs. The nucleation and crystallization kinetics of TTFA-Pb and BTFA-Pb from sol-gel to film were investigated using in situ optical microscopy and in situ grazing incidence wide-angle X-ray scattering (GIWAXS) measurements. It is found that the TTFA spacer could reduce the energy barrier of nucleation and induces crystal vertical orientation of 2D perovskite by forming larger clusters in precursor solution, resulting in much improved film quality. Benefiting from the enlarged crystal grains, reduced exciton binding energy, and decreased electron-phonon coupling coefficient, the photovoltaic device based on (TTFA)2 MAn-1 Pbn I3n+1 (n=5) achieved a champion efficiency of 19.41 %, which is a record for 2D RP PSCs with FA-based spacers. Our work provides deep understanding of the nucleation and crystallization process of 2D RP perovskite films and highlights the great potential of FA-based semiconductor spacers in highly efficient 2D PSCs.

Developing and validating a Domain-specific Grit Scale for College Athletic Students.

The aim of this study was to create and validate a ten-item Domain-specific Grit Scale for College Athletic Students (DGSCAS) to assess the level of grit among college athletic students. College athletic students from a single independent college located in a northern city in China (526 participants at time 1 and 589 participants at time 2) were assessed according to the scale. Various analyses were conducted in this study, including exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and measurement invariance analysis across different sex and birthplaces. The results of the EFA revealed two factors: consistency of interests and perseverance of effort. The CFA results demonstrated acceptable fit indices (x2 = 160.048, df = 34, x2/df = 4.707, CFI = 0.983, TLI = 0.978, SRMR = 0.021, and RMSEA = 0.079). The scale exhibited satisfactory convergent validity and discriminant validity. The significant correlation of these factors with the Grit scale provided strong evidence of criterion-related validity. Measurement invariance analysis indicated that the scale performed consistently across different sex and birthplaces. Three limitations and corresponding recommendations were discussed, including sample heterogeneity, the lack of a unified test result as a criterion for predictive validity, and the cross-sectional design of the study. In conclusion, the DGSCAS is a practical and validated instrument that can be used to assess the level of grit among college athletic students in an educational context.

Recent Progress of Layered Perovskite Solar Cells Incorporating Aromatic Spacers.

Layered two dimensional (2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites can be obtained by cutting 3D perovskites along < 100 > orientation by incorporation of bulky organic spacers, which play a key role in the performance of 2D perovskite solar cells (PSCs). Compared with aliphatic spacers, aromatic spacers with high dielectric constant have the potential to decrease the dielectric and quantum confinement effect of 2D perovskites, promote efficient charge transport and reduce the exciton binding energy, all of which are beneficial for the photovoltaic performance of 2D PSCs. In this review, we aim to provide useful guidelines for the design of aromatic spacers for 2D perovskites. We systematically reviewed the recent progress of aromatic spacers used in 2D PSCs. Finally, we propose the possible design strategies for aromatic spacers that may lead to more efficient and stable 2D PSCs.

Orbital Interactions between the Organic Semiconductor Spacer and the Inorganic Layer in Dion-Jacobson Perovskites Enable Efficient Solar Cells.

2D Dion-Jacobson (DJ) perovskites have become emerging photovoltaic materials owing to their intrinsic structure stability. However, as insulating aliphatic cations are widely used as spacers, the interactions between the spacers and inorganic layers in DJ perovskites have rarely been studied. Here, an organic semiconductor spacer with two covalently connected thiophene rings, namely bithiophene dimethylammonium (BThDMA), is successfully developed for 2D DJ perovskite solar cells (PSCs). An important finding is that there are strong orbital interactions between the conjugated organic spacer and adjacent inorganic layers, whereas no such interactions exist in DJ perovskite using an aliphatic octane-1,8-diaminium (ODA) spacer with similar length. The BThDMA spacer with multiple conjugated aromatic rings can also induce crystal growth with large grain size and preferred vertical orientation, resulting in reduced trap density and improved charge-carrier mobility. As a result, the optimized device based on (BThDMA)MAn -1 Pbn I3 n +1 (nominal n = 5) shows an excellent PCE of 18.1% with negligible hysteresis, which is a record efficiency for 2D DJ PSCs using a spacer with two or more covalently linked aromatic rings. These findings provide a novel and important insight on achieving efficient and stable 2D DJ perovskite solar cells by developing organic semiconductor spacers.

Ultralong Carrier Lifetime Exceeding 20 µs in Lead Halide Perovskite Film Enable Efficient Solar Cells.

The carrier lifetime is one of the key parameters for perovskite solar cells (PSCs). However, it is still a great challenge to achieve long carrier lifetimes in perovskite films that are comparable with perovskite crystals owning to the large trap density resulting from the unavoidable defects in grain boundaries and surfaces. Here, by regulating the electronic structure with the developed 2-thiopheneformamidinium bromide (ThFABr) combined with the unique film structure of 2D perovskite layer caped 2D/3D polycrystalline perovskite film, an ultralong carrier lifetime exceeding 20 µs and carrier diffusion lengths longer than 6.5 µm are achieved. These excellent properties enable the ThFA-based devices to yield a champion efficiency of 24.69% with a minimum VOC loss of 0.33 V. The unencapsulated device retains ≈95% of its initial efficiency after 1180 h by max power point (MPP) tracking under continuous light illumination. This work provides important implications for structured 2D/(2D/3D) perovskite films combined with unique FA-based spacers to achieve ultralong carrier lifetime for high-performance PSCs and other optoelectronic applications.

Crystal Growth Regulation of 2D/3D Perovskite Films for Solar Cells with Both High Efficiency and Stability.

Reducing the electronic defects in perovskite films has become a substantial challenge to further boost the photovoltaic performance of perovskite solar cells. Here, 2D (NpMA)2 PbI4 perovskite and 1-naphthalenemethylammonium iodide (NpMAI) are separately introduced into the PbI2 precursor solutions to regulate the crystal growth in a 2D/3D perovskite film using a two-step deposition method. The (NpMA)2 PbI4 modulated perovskite film shows a significantly improved film quality with enlarged grain size from ≈500 nm to over 1000 nm, which greatly reduces the grain-boundary defects, improves the charge carrier lifetime, and hinders ionic diffusion. As a result, the best-performing device shows a high power conversion efficiency (PCE) of 24.37% for a small-area (0.10 cm-2 ) device and a superior PCE of 22.26% for a large-area (1.01 cm-2 ) device. Importantly, the unencapsulated device shows a dramatically improved operational stability with maintains over 98% of its initial efficiency after 1500 h by maximum power point (MPP) tracking under continuous light irradiation.

Highly Efficient and Stable Dion-Jacobson Perovskite Solar Cells Enabled by Extended π-Conjugation of Organic Spacer.

2D Dion-Jacobson (DJ) perovskites have become an emerging photovoltaic material with excellent structure and environmental stability due to their lacking van der Waals gaps relative to 2D Ruddlesden-Popper perovskites. Here, a fused-thiophene-based spacer, namely TTDMAI, is successfully developed for 2D DJ perovskite solar cells. It is found that the DJ perovskite using TTDMA spacer with extended π-conjugation length exhibits high film quality, large crystal size and preferred crystal vertical orientation induced by the large crystal nuclei in precursor solution, resulting in lower trap density, reduced exciton binding energy and oriented charge transport. As a result, the optimized 2D DJ perovskite device based on TTDMA (nominal n = 4) delivers a champion PCE up to 18.82%. Importantly, the unencapsulated device based on TTDMA can sustain average 99% of their original efficiency after being stored in N2 for 4400 h (over 6 months). Moreover, light, thermal, environmental and operational stabilities are also significantly improved in comparison with their 3D counterparts.