The notorious defects in the grain boundaries (GBs) and surfaces trigger serious nonradiative recombination and interfacial charge losses, concomitantly exacerbating the deterioration of photovoltaic performance and phase stability of CsPbI2Br perovskite solar cells. In this work, a comprehensive dual-passivation strategy enabled by formamidine salts (FADP) is developed to annihilate defects both inside the GBs and over the surface. It is shown that formamidinothiourea (FATU) additive could effectively modulate crystallization and afford to passivate both shallow-/deep-level defects at GBs, thereby endowing CsPbI2Br films with reduced lattice micro-strains and enlarged grains over 2 μm. Meanwhile, formamidinium bromine (FABr) post-treatment can efficiently heal the defective surface and realize cationic exchange with below CsPbI2Br films, forming a gradient band alignment at the CsPbI2Br/HTL interface. Profiting from ameliorated crystallization, inhibited GBs/surface charge recombination and facilitated hole transport ability, the novel FADP strategy substantially lifts the Voc from 1.22 V to 1.34 V, yielding a champion PCE of 16.74% with greatly reduced hysteresis. Coincidently, the unencapsulated FADP devices maintained 86.2% of initial PCE after aging at 25% RH for 40 days and 83.8% after 480 h aging under continuous illumination, which is pertinent to the inhibited defective region as well as Br-rich surface.
Low bandgap tin–lead halide perovskite (PVSK) presents promising opportunities for high‐performance solar cells. However, the randomly crystallized Sn–Pb PVSK with a tin‐rich surface is easily oxidized, leading to high‐level p‐type doping, which hinders the performance enhancement of the solar cell devices. Herein, an efficient anti‐solvent passivation strategy to regulate defect, crystallization, and energy conversion performance based on anti‐solvents composed of chlorobenzene, isopropanol, and methylammonium chloride (MACl) is proposed. It is shown that the Sn–Pb PVSK film gets more moderate and order, with less PbI 2 and more α‐phase PVSK formed. Furthermore, it is revealed that the surface of the as‐processed film is Pb‐rich, demonstrating a decrease in the surface p‐type concentration, which is more suitable for the photoelectric conversion enhancement of the inverting device. Finally, the MACl‐assisted post‐treated Sn–Pb PVSK invert solar cells exhibit a high current density of 26.49 mA cm −2 with a open‐circuit voltage of 0.70 V and a power conversion efficiency of 16.05%. The modified anti‐solvent process fuses the advantage of additive and anti‐solvent engineering for growing highly crystallized hybrid tin‐lead halide PVSK for photovoltaic devices.
This review summarizes the influence mechanism, research progress and future perspectives on perovskite stability from the perspectives of [PbX 6 ] 4− octahedra and organic spacers.
Tin (Sn)-based and mixed tin–lead (Sn–Pb) perovskites have attracted increased attention as promising candidates for new generation lead-free perovskite and all-perovskite tandem solar cells. However, as an inevitably critical issue, Sn(II) induced serious defects and oxidation and caused poor photovoltaic performance and unsatisfactory stability for Sn-based and mixed Sn–Pb perovskites. Herein, a comprehensive understanding on defect classification, defect formation, defect effect on performance, and defect passivation strategies is reviewed on the Sn(II) induced defects. The Sn(II)-based defects can be classified from the aspects of defect dimensions and shallow/deep levels in energy structure according to three main origins, i.e. low defect tolerance, oxidation, and fast crystallization. Then, the state-of-the-art defect passivation strategies including surface Lewis acid/base coordination, low/mixed dimensional perovskite design, composition regulation and crystal orientation modulation, and reducing agent assistance are summarized systematically. Lastly, several key scientific issues and future research prospectives are proposed for achieving stable and high-performance Sn-related perovskite photovoltaics.
Skyline Solar Inc. has developed a novel silicon-based PV system to simultaneously reduce energy cost and improve scalability of solar energy. The system achieves high gain through a combination of high capacity factor and optical concentration. The design approach drives innovation not only into the details of the system hardware, but also into manufacturing and deployment-related costs and bottlenecks. The result of this philosophy is a modular PV system whose manufacturing strategy relies only on currently existing silicon solar cell, module, reflector and aluminum parts supply chains, as well as turnkey PV module production lines and metal fabrication industries that already exist at enormous scale. Furthermore, with a high gain system design, the generating capacity of all components is multiplied, leading to a rapidly scalable system. The product design and commercialization strategy cooperate synergistically to promise dramatically lower LCOE with substantially lower risk relative to materials-intensive innovations. In this paper, we will present the key design aspects of Skyline's system, including aspects of the optical, mechanical and thermal components, revealing the ease of scalability, low cost and high performance. Additionally, we will present performance and reliability results on modules and the system, using ASTM and UL/IEC methodologies.
Open-circuit voltage loss and instability from surface Sn(II) oxidation and high-density Sn vacancies pose great hurdles for developing high-performance Sn-based perovskite solar cells (PSCs). Turning attention from the bulk microstructure to surface reconstruction is promising to push the performance enhancement of Sn-based PSCs. Herein, a surface-modulation strategy based on 6-maleimidohexanehydrazide trifluoroacetate is rationally designed to reconstruct the surface structure of FASnI3 films to manage the Fermi level and passivate defects. The electronic state evolution results in an n-type Fermi level shift of the shallow surface, thereby forming an extra back-surface field for electron extraction. Meanwhile, the ion-pairing agent affords passivating cationic and anionic defects, thereby nullifying the charged-defect-rich surface. In particular, the reductive hydrazide group and carboxyl groups alleviate superficial Sn(IV) and inhibit Sn(IV) formation, homogenizing surface potential and prolonging carrier lifetime. Accordingly, devices deliver a champion power conversion efficiency (PCE) of 13.64% and an elongated lifespan, with over 75% of the original PCE after 1000 h of illumination (O2 < 50 ppm). This work presents a new insight on the surface reconstruction strategy for developing high-performance Sn-based PSCs.
Despite the conspicuous achievements in perovskite solar cells (PSCs), further improvement of the power conversion efficiency (PCE) is hindered by substantially detrimental carrier recombination resulting from the high interfacial charge defect density and inferior charge transport kinetics. Herein, an interface engineering strategy is developed to introduce a Lewis base thiophene or thiazole–modified C 3 N 4 layer at the electron transfer layer (ETL)/perovskite interface to constitute a stepwise energy band alignment and passivate defects at interfaces of the perovskite film. Attributed to its well‐matched energy level with TiO 2 and perovskite, the charge extraction efficiency and charge transfer dynamics can be promoted remarkably, greatly inhibiting charge recombination at the interface. Furthermore, thiophene and thiazole can donate the lone pair electrons in S or N atoms to undercoordinated Pb 2+ , which effectively passivates the electronic trap states caused by halogen vacancies, thereby greatly minimizing trap‐assisted nonradiative recombination in the PSCs. Eventually, the thiazole–C 3 N 4 /perovskite‐based devices acquire an outstanding efficiency of 19.23%, supported by an enhanced open‐circuit voltage ( V OC ) of 1.11 V with improved moisture stability. This work provides an avenue for interfacial energy level modulation and defect passivation strategies for a rational interface microstructure design for meliorating the performance of PSCs.
Although the incorporation of 2D perovskite into 3D perovskite can greatly enhance intrinsic stability, power conversion efficiency (PCE) of 2D/3D perovskite is still inferior to its 3D counterpart due to poor carrier transport kinetics resulted from the quantum and dielectric confinement of 2D component. To overcome this issue, the electron acceptor molecule 1,2,4,5-tetracyanobenzene (TCNB) was introduced to trigger intermolecular π-π interaction in 2D perovskite along with the electronic doping of 2D/3D perovskite to improve charge transfer efficiency. By virtue of high electron affinity, TCNB can undergo electron transfer reaction and subsequently establish π-π interaction with 1-naphthalenemethylammonium (NMA) cations, greatly strengthening lattice rigidity and reducing exciton binding energy. Transmission electron microscopy results demonstrate that 2D phases are mainly distributed at grain boundaries, reducing defect density and weakening nonradiative recombination. Meanwhile, the p-type doping of perovskite by TCNB optimizes energy level alignment at perovskite/hole transport layer interface. Consequently, PCE of champion device is significantly boosted to 24.01 %. The unencapsulated device retains an initial efficiency close to 94 % after exposure to ambient environment for over 1000 h. This work paves a novel path for designing new mixed-dimensional perovskite solar cells with high PCE and superior stability.
Abstract Due to the relatively inferior dielectric constant, Sn‐based perovskites exhibit lower defect tolerance and insufficient dielectric shielding effect compared with Pb‐perovskites. Upgrading built‐in electric field (BEF) in Sn‐based perovskite solar cells (PSCs) can be effective to reduce large voltage deficit and improve poor performance caused by the low defect tolerance resulting from the intrinsic inferior dielectric of Sn‐based perovskites. Herein, 2‐methylbenzimidazole (MBI) molecular ferroelectric with low coercive field and high Curie‐temperature is introduced to construct an additional ferroelectric field in FASnI 3 ‐based PSCs. The ferroelectric effect of MBI can promote exciton dissociation, enhance carrier population, and suppress the adverse effect of the residual defects on carriers, and the directional polarization of MBI in FASnI 3 film can be driven by the BEF in PSCs to broaden the width of depletion region. Additionally, the MBI molecules with amine functional groups effectively regulate perovskite crystallization, passivate Sn‐related defects, and enhance the oxidation barrier. Profiting from the above advantages, the MBI‐modified device achieves a champion power conversion efficiency (PCE) of 12.91%, keeping over 94% average PCE after 1056 h in N 2 glovebox for the unencapsulated device. This study highlights the significant role of molecular ferroelectrics in perovskite photovoltaics.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(144 450 300)'/%3e%3cuse xlink:href='%23a' transform='rotate(216 450 300)'/%3e%3cuse xlink:href='%23a' transform='rotate(288 450 300)'/%3e%3c/svg%3e)