The electron transport layer (ETL) is a key component of regular perovskite solar cells to promote the overall charge extraction efficiency and tune the crystallinity of the perovskite layer for better device performance. The authors present a novel protocol of ETL engineering by incorporating a composition of the perovskite precursor, methylammonium chloride (MACl), or formamidine chloride (FACl), into SnO 2 layers, which are then converted into the crystal nuclei of perovskites by reaction with PbI 2 . The SnO 2 -embedded nuclei remarkably improve the morphology and crystallinity of the optically active perovskite layers. The improved ETL-to-perovskite electrical contact and dense packing of large-grained perovskites enhance the carrier mobility and suppress charge recombination. The power conversion efficiency increases from 20.12% (blank device) to 21.87% (21.72%) for devices with MACl (FACl) as an ETL dopant. Moreover, all the precursor-engineered cells exhibit a record-high fill factor (82%).

Choline chloride as a photosynthesis promoter is important for increasing plant yield, and we have found that it has a similar effect in perovskite solar cells (PSCs). Here, we propose the innovation of using molecular self-assembly methods to produce a choline chloride monolayer on the surface of the SnO 2 ; this monolayer works as a passivation layer that reduces the surface oxygen vacancies and improves the performance of CH 3 NH 3 PbI 3 (MAPbI 3 ) PSCs. The MAPbI 3 PSC based on SnO 2 modified by choline chloride (Chol-SnO 2 ) electron transport layer (ETL) achieves an optimal power conversion efficiency (PCE) of 18.90% under one solar illumination. The PCE is increased by 10−25% compared to the device without modification, and hysteresis is significantly reduced by eliminating the charge accumulation between the interface of the perovskite and ETL. More importantly, the MAPbI 3 PSC based on Chol-SnO 2 ETL exhibits a higher open-circuit voltage (V OC ) of 1.145 V compared to the control device (1.071 V). This work provides a very simple and effective way to improve PSC performance, which has long-term significance for the sustainable development of energy.

Co-modification of an electron transport layer (ETL) with metal oxides and organic molecules can optimize the structure of the ETL and improve the performance of perovskite solar cells (PSCs).

Coral reef has a unique dendritic structure with large specific surface area, rich pore structure, so that it can be attached to a large number of zooxanthellae for gas exchange. Coral reef ecosystems are also known as underwater rainforests. Inspired by this biological structure, we designed and fabricated coral-like Co3O4 decorated N-doped carbon particles (Co3O4/N-CP). The obtained Co3O4/N-CP-900 catalyst shows efficient ORR electrocatalytic performances in an alkaline medium with a positive onset and half-wave potentials of 0.97 and 0.90 V (vs. RHE), as well as a high diffusion-limited current density (5.50 mA cm−2) comparable to that of a Pt/C catalyst (5.15 mA cm−2). It also displays better stability and methanol tolerance than commercial Pt/C. In addition, the Co3O4/N-CP-900 electrode has a high specific capacitance of 316.2 F g−1 in 6 M KOH, as well as good rate capabilities and excellent cycle performance. These results are due to large surface area, narrow pore size distribution, high density electrochemical energy conversion and storage activity centers. This method presented here offers an effective path for the development of high performance multi-functional carbon-based materials for ORR and supercapacitor applications.

The photovoltaic property of perovskite solar cells (PSCs) is affected by detrimental defects located at the bulk and surface of perovskite films. Furthermore, defect passivation of the perovskite films is challenging. Herein, we add solid CsCl to PbI 2 precursor solutions to adjust the properties of PbI 2 membranes and obtain perovskite layers with a micrometer-sized grain by reducing grain boundary defects. Bulk defects are reduced by the increase in grain size and decrease in grain boundaries. Fewer bulk defects and the incorporation of Cs increase the device performance, improving the power conversion efficiency (PCE) from 19.72% to 22.24% and suppressing hysteresis. The passivation of surface defects further increases the PCEs and open-circuit voltages (V OC ) of PSCs. Therefore, we use 4-methoxyphenethylamine (CH 3 O−PEAI) to modify the CsCl perovskite films to eliminate the surface defects and suppress nonradiative charge recombination. The surface defect passivation using CH 3 O−PEAI further improves the PCE of the PSCs to 23.25% with a V OC of 1.186 V, resulting in more efficient and stable PSCs.