Perovskite solar cells (PSCs) have become a promising photovoltaic (PV) technology, where the evolution of the electron‐selective layers (ESLs), an integral part of any PV device, has played a ...distinctive role to their progress. To date, the mesoporous titanium dioxide (TiO2)/compact TiO2 stack has been among the most used ESLs in state‐of‐the‐art PSCs. However, this material requires high‐temperature sintering and may induce hysteresis under operational conditions, raising concerns about its use toward commercialization. Recently, tin oxide (SnO2) has emerged as an attractive alternative ESL, thanks to its wide bandgap, high optical transmission, high carrier mobility, suitable band alignment with perovskites, and decent chemical stability. Additionally, its low‐temperature processability enables compatibility with temperature‐sensitive substrates, and thus flexible devices and tandem solar cells. Here, the notable developments of SnO2 as a perovskite‐relevant ESL are reviewed with emphasis placed on the various fabrication methods and interfacial passivation routes toward champion solar cells with high stability. Further, a techno‐economic analysis of SnO2 materials for large‐scale deployment, together with a processing‐toxicology assessment, is presented. Finally, a perspective on how SnO2 materials can be instrumental in successful large‐scale module and perovskite‐based tandem solar cell manufacturing is provided.
Notable developments of SnO2 as an electron‐selective layer for efficient perovskite solar cells (PSCs) are reviewed, along with an overview of the fabrication methods and interfacial passivation routes. Furthermore, techno‐economic and toxicology analyses of SnO2 are discussed for possible large‐scale deployment of PSCs. Finally, the role of SnO2 in scaled module and tandem solar cell production is revealed.
Hybrid organic–inorganic semiconducting perovskite photovoltaic cells are usually coupled with organic hole conductors. Here, we report planar, inverse CH3NH3PbI3–x Cl x -based cells with inorganic ...hole conductors. Using electrodeposited NiO as hole conductor, we have achieved a power conversion efficiency of 7.3%. The maximum V OC obtained was 935 mV with an average V OC value being 785 mV. Preliminary results for similar cells using electrodeposited CuSCN as hole conductor resulted in devices up to 3.8% in efficiency. The ability to obtain promising cells using NiO and CuSCN expands the presently rather limited range of available hole conductors for perovskite cells.
A fluoride boostThe wide-bandgap perovskite layer in perovskite-silicon tandem solar cells is still limited by high interface recombination at the electron extraction interface. Liu et al. show that ...adding an ultrathin magnesium fluoride interlayer between the perovskite and C60 electron transport layer during growth facilitates mitigated nonradiative recombination. An analysis of electronic structural data showed that conduction band bending of the perovskite and C60 facilitated electron extraction. A monolithic perovskite-silicon tandem solar cell with a certified power conversion efficiency of 29.3% retained about 95% of its initial performance for 1000 hours. —PDS
If perovskite solar cells (PSCs) with high power conversion efficiencies (PCEs) are to be commercialized, they must achieve long-term stability, which is usually assessed with accelerated degradation ...tests. One of the persistent obstacles for PSCs has been successfully passing the damp-heat test (85°C and 85% relative humidity), which is the standard for verifying the stability of commercial photovoltaic (PV) modules. We fabricated damp heat-stable PSCs by tailoring the dimensional fragments of two-dimensional perovskite layers formed at room temperature with oleylammonium iodide molecules; these layers passivate the perovskite surface at the electron-selective contact. The resulting inverted PSCs deliver a 24.3% PCE and retain >95% of their initial value after >1000 hours at damp-heat test conditions, thereby meeting one of the critical industrial stability standards for PV modules.
Highly reproducible and reversible thermochromic nature of dihydrated methylammonium lead iodide is found. A wide bandgap variation of the material (∼2 eV) is detected between room temperature and 60 ...°C under ambient condition as a result of phase transition caused by moisture absorption and desorption. In situ X-ray diffraction and Fourier transform infrared spectroscopy studies are performed to understand the mechanistic behavior during the phase transition. This thermochromic property is further explored as absorber material in mesostructured solar cells. Temperature-dependent reversible power conversion efficiency greater than 1% under standard test conditions is demonstrated; revealing its potential applicability in building integrated photovoltaics.
Highly efficient perovskite solar cells (PSCs) fabricated in the classic n–i–p configuration generally employ triphenylamine-based hole-transport layers (HTLs) such as spiro-OMeTAD, PTAA, and ...poly-TPD. Controllable doping of such layers has been critical to achieve increased conductivity and high device performance. To this end, LiTFSI/tBP doping and subsequent air exposure is widely utilized. However, this approach often leads to low device stability and reproducibility. Departing from this point, we introduce the Lewis acid tris(pentafluorophenyl)borane (TPFB) as an effective dopant, resulting in a significantly improved conductivity and lowered surface potential for triphenylamine-based HTLs. Here, we specifically investigated spiro-OMeTAD, which is the most widely used HTL for n–i–p devices, and revealed improved power conversion efficiency (PCE) and stability of the PSCs. Further, we demonstrated the applicability of TPFB doping to other triphenylamine-based HTLs. Spectroscopic characterizations reveal that TPFB doping results in significantly improved charge transport and reduced recombination losses. Importantly, the TPFB-doped perovskite devices retained near 85% of the initial PCE after 1000 h of storage in the air, while the conventional LiTFSI-doped device dropped to 75%. Finally, we give insight into utilizing other similar molecular dopants such as fluorine-free triphenylborane and phosphorus-centered tris(pentafluorophenyl)phosphine (TPFP) by density functional theory analysis underscoring the significance of the central boron atom and fluorination in TPFB for the formation of Lewis acid–base adducts.
Though perovskite solar cells (PSC) have reached high efficiency comparable to its counterparts, it is still striving towards finding a strong hold in terms of long-term stability. Several approaches ...have been made to prevent the degradation of PSC. Here, we present low-temperature ALD deposited Al2O3 as an effective encapsulant for PSC. The encapsulated devices improve with PCE reaching up to 19.4% post 300 cycles of Al2O3 deposition. In-situ QCM and FTIR measurements reveal that trimethylaluminum gets trapped inside the spiro-OMeTAD layer and is available for the subsequent dosage of H2O during nucleation regime. Here we unveil the fact that the ALD grown Al2O3 is not only surface limited, but the material penetrates the spiro-OMeTAD and enhances the hole transport property, improving the overall performance of encapsulated cells. Intermittent measurements indicate that encapsulated cells are stable, retaining 84% of its initial efficiency by the end of 300 days. Subsequently we elucidate that the device measurements under continuous illumination and with different bias conditions and atmosphere show that the ALD grown encapsulation prevents ingress of moisture and oxygen into the cells maintaining their stability.
•ALD-Al2O3 encapsulated PSC retained 84% of initial efficiency by the end of 300 days of intermittent measurement in ambient.•In-situ QCM showed non-linearity in mass change until a complete surface coverage after which it reaches the linear growth regime.•In-situ FTIR revealed continuous addition of Al–CH3 on the bulk of spiro-OMeTAD upon TMA exposure during the nucleation regime.
With the rapid rise in device performance of perovskite solar cells (PSCs), overcoming instabilities under outdoor operating conditions has become the most crucial obstacle toward their ...commercialization. Among stressors such as light, heat, voltage bias, and moisture, the latter is arguably the most critical, as it can decompose metal‐halide perovskite (MHP) photoactive absorbers instantly through its hygroscopic components (organic cations and metal halides). In addition, most charge transport layers (CTLs) commonly employed in PSCs also degrade in the presence of water. Furthermore, photovoltaic module fabrication encompasses several steps, such as laser processing, subcell interconnection, and encapsulation, during which the device layers are exposed to the ambient atmosphere. Therefore, as a first step toward long‐term stable perovskite photovoltaics, it is vital to engineer device materials toward maximizing moisture resilience, which can be accomplished by passivating the bulk of the MHP film, introducing passivation interlayers at the top contact, exploiting hydrophobic CTLs, and encapsulating finished devices with hydrophobic barrier layers, without jeopardizing device performance. Here, existing strategies for enhancing the performance stability of PSCs are reviewed and pathways toward moisture‐resilient commercial perovskite devices are formulated.
Perovskite solar cells have attracted significant attention for commercialization. However, their intrinsic instabilities due to their high susceptibility to moisture cause irreversible perovskite degradation and device failures must be addressed. This article discusses extensively all available strategies to make perovskite solar cells, before final encapsulation, as moisture resilient as possible.
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