Thermal-Radiation-Driven Ultrafast Crystallization of Perovskite Films Under Heavy Humidity for Efficient Inverted Solar Cells.

Fabricating perovskite solar cells (PSCs) in air is conducive to low-cost commercial production; nevertheless, it is rather difficult to achieve comparable device performance as that in an inert atmosphere because of the poor moisture toleration of perovskite materials. Here, the perovskite crystallization process is systematically studied using two-step sequential solution deposition in an inert atmosphere (glovebox) and air. It is found that moisture can stabilize solvation intermediates and prevent their conversion into perovskite crystals. To address this issue, thermal radiation is used to accelerate perovskite crystallization for integrated perovskite films within 10 s in air. The as-formed perovskite films are compact, highly oriented with giant grain size, superior photoelectric properties, and low trap density. When the films are applied to PSC devices, a champion power conversion efficiency (PCE) of 20.8% is obtained, one of the best results for air-processed inverted PSCs under high relative humidity (60 ± 10%). This work substantially assists understanding and modulation to perovskite crystallization kinetics under heavy humidity. Also, the ultrafast conversion strategy by thermal radiation provides unprecedented opportunities to manufacture high-quality perovskite films for low-temperature, eco-friendly, and air-processed efficient inverted PSCs.

Bridging the Interfacial Contact for Improved Stability and Efficiency of Inverted Perovskite Solar Cells.

Inverted perovskite solar cells (PSCs) have received widespread attention due to their facile fabrication and wide applications. However, their power conversion efficiency (PCE) is reported lower than that of regular PSCs because of the undesirable interfacial contact between perovskite and the hydrophobic hole transport layer (HTL). Here, an interface regulation strategy is proposed to overcome this limitation. A small molecule ([2-(9H-carbazol-9-yl) ethyl] phosphonic acid, abbreviated as 2P), composed of carbazole and phosphonic acid groups, is inserted between perovskite and HTL. Morphological characterization and theoretical calculation reveal that perovskite bonds stronger on 2P-modified HTL than on pristine HTL. The improved interfacial contact facilitates hole extraction and retards degradation. Upon the incorporation of 2P, inverted PSCs deliver a high PCE of over 22% with superior stability, keeping 84.6% of initial efficiency after 7200 h storage under an ambient atmosphere with a relative humidity of ≈30-40%. This strategy provides a simple and efficient way to boost the performance of inverted PSCs.

Doping Free and Amorphous NiOx Film via UV Irradiation for Efficient Inverted Perovskite Solar Cells.

High crystallization and conductivity are always required for inorganic carrier transport materials for cheap and high-performance inverted perovskite solar cells (PSCs). High temperature and external doping are inevitably introduced and thus greatly hamper the applications of inorganic materials for mass production of flexible and tandem devices. Here, an amorphous and dopant-free inorganic material, Ni3+ -rich NiOx , is reported to be fabricated by a novel UV irradiation strategy, which is facile, easily scaled-up, and energy-saving because all the processing temperatures are below 82 â„ƒ. The as-prepared NiOx film shows highly improved conductivity and hole extraction ability. The rigid and flexible PSCs present the champion efficiencies of 22.45% and 19.7%, respectively. This work fills the gap of preparing metal oxide films at the temperature below 150 °C for inverted PSCs with the high efficiency of >22%. More importantly, this work upgrades the substantial understanding about inorganic materials to function well as efficient carrier transport layers without external doping and high crystallization.