penghuang

An electron-transport layer (ETL) that selectively collects photogenerated electrons is an important constituent of halide perovskite solar cells (PSCs). Although TiO₂ films are widely used as ETL of PSCs, the processing of TiO₂ films with high electron mobility requires high-temperature annealing and TiO₂ dissociates the perovskite layer through a photocatalytic reaction. Here, we report an effective surface-modification method of a room-temperature processed ZnO nanoparticles (NPs) layer as an alternative to the TiO₂ ETL. A combination of simple UV exposure and nitric acid treatment effectively removes the hydroxyl group and passivates surface defects in ZnO NPs. The surface modification of ZnO NPs increases the power conversion efficiency (PCE) of PSCs to 14 % and decreases the aging of PSCs under light soaking. These results suggest that the surface-modified ZnO film can be a good ETL of PSCs and provide a path toward low-temperature processing of efficient and stable PSCs that are compatible with flexible electronics.

A special treatment: We report an effective surface-modification method of a room-temperature processed ZnO nanoparticles layer as an alternative to the TiO₂ electron-transport layer. A combination of simple UV exposure and nitric acid treatment effectively removes the hydroxyl group and passivates surface defects in ZnO nanoparticles.

It is commonly believed that excess PbI₂ has beneficial effects for perovskite solar cells owing to the modification of charge-transport behavior at interfaces, by surface passivation and by blocking electron-hole recombination. Here, we introduce a dynamically dispensed spin-coating technique in a two-step deposition to form a perovskite layer with controllable quantities of crystalline PbI₂. Using this technique, the concentration of CH₃NH₃I solution is kept constant at the reaction interface, ensuring smooth growth of films. By changing the spinning rate during the reaction, the PbI₂ conversion ratio and perovskite cuboid size can be optimized, resulting in a power conversion efficiency improvement over control devices. This dynamically dispensed technique represents a repeatable method for compositional control in perovskite solar cells and improves our understanding of how a PbI₂ blocking layer improves the performance of perovskite solar cells.

Dynamic spinning: We introduce a dynamically dispensed spin-coating technique in a two-step deposition to form a perovskite layer with controllable quantities of crystalline PbI₂. Using this technique, the concentration of CH₃NH₃I solution is kept constant at the reaction interface, ensuring smooth growth of films for use in perovskite solar cells.

The chloride-doped CH₃NH₃PbI_3−xCl_x perovskite has attracted great attention owing to clear performance enhancement by using a Cl additive and by the controversial arguments on Cl function and the mechanism behind it. Herein, a series of CH₃NH₃PbI_3−xCl_x perovskites with various Cl content was prepared through a gas/solid reaction between CH₃NH₂ gas and HPbI_3−xCl_x (x=0–1). The small amount of Cl doping in CH₃NH₃PbI_3−xCl_x (x=0.05) could lead to band gap broadening and significantly increase the perovskite grain size, and the phase-pure CH₃NH₃PbI_2.95Cl_0.05 perovskites exhibited up to 17.44 % efficiency. For Cl contents higher than 0.1 (x>0.1), CH₃NH₃PbCl₃ formed and coexisted with CH₃NH₃PbI_3−xCl_x, and CH₃NH₃PbCl₃ could help to improve the thermal stability of CH₃NH₃PbI_3−xCl_x. However, the excessive co-existing wide-band-gap CH₃NH₃PbCl₃ perovskites would inhibit the electron transfer and lead to a deterioration of photovoltaic performance.

Doped perovskites: A serial of CH₃NH₃PbI_3−xCl_x perovskites with fixed 1:3 molar ratio of Pb to halide are investigated. The small amount of Cl doping affects the crystallinity and grain size of the perovskite crystal, achieving a power conversion efficiency of 17.44 %. In contrast, the excessive CH₃NH₃PbCl₃ perovskite in CH₃NHPbI_3−xCl_x (x>0.33) can retard the electron transfer and lowers the performance.

Organic–inorganic perovskites with intriguing optical and electrical properties have attracted significant research interests due to their excellent performance in optoelectronic devices. Recent efforts on preparing uniform and large-grain polycrystalline perovskite films have led to enhanced carrier lifetime up to several microseconds. However, the mobility and trap densities of polycrystalline perovskite films are still significantly behind their single-crystal counterparts. Here, a facile topotactic-oriented attachment (TOA) process to grow highly oriented perovskite films, featuring strong uniaxial-crystallographic texture, micrometer-grain morphology, high crystallinity, low trap density (≈4 × 10¹⁴ cm⁻³), and unprecedented 9 GHz charge-carrier mobility (71 cm² V⁻¹ s⁻¹), is demonstrated. TOA-perovskite-based n-i-p planar solar cells show minimal discrepancies between stabilized efficiency (19.0%) and reverse-scan efficiency (19.7%). The TOA process is also applicable for growing other state-of-the-art perovskite alloys, including triple-cation and mixed-halide perovskites.

A facile topotactic-oriented attachment process can produce uniaxially oriented perovskite thin films with micrometer-grain morphology, high crystallinity, low trap density (≈4 × 10¹⁴ cm⁻³), and fast 9 GHz charge-carrier mobility (71 cm² V⁻¹ s⁻¹). The n-i-p planar perovskite solar cell exhibits a power conversion efficiency of 19.7% (with stabilized efficiency output of 19.0%).

Minimization of defects in absorber materials is essential for hybrid perovskite solar cells, especially when constructing thick polycrystalline layers in a planar configuration. Here, a simple methylamine solution-based additive is reported to improve film quality with nearly an order of magnitude reduction in intrinsic defect concentration. In the resultant film, an increase in carrier lifetime as a result of a decrease in shallow electronic disorder is observed. This superior crystalline film quality is further evidenced via a doubled spin relaxation time as compared with other reports. Bearing sufficient carrier diffusion length, a thick absorber layer (≈650 nm) is implemented in planar devices to achieve a champion power conversion efficiency of 20.02% with a stabilized output efficiency of 19.01% under one sun illumination. This work demonstrates a simple approach to improve hybrid perovskite film quality by substantial reduction of intrinsic defects for wide applications in optoelectronics.

A simple methylamine solution-based additive to improve film quality with nearly an order of magnitude reduction in the concentration of intrinsic defects is reported, and the relevant perovskite solar cells achieve a champion power conversion efficiency of 20.02% with a stabilized output efficiency of 19.01% under 1 sun illumination.