Supporting Videos SI

Hybrid organometal halide perovskites are known for their excellent optoelectronic functionality as well as their wide-ranging chemical flexibility. The composition of hybrid perovskite devices has trended toward increasing complexity as fine-tuned properties are pursued, including multielement mixing on the constituents A and B and halide sites. However, this tunability presents potential challenges for charge extraction in functional devices. Poor consistency and repeatability between devices may arise due to variations in composition and microstructure. Within a single device, spatial heterogeneity in composition and phase segregation may limit the device from achieving its performance potential. This review details how the nanoscale elemental distribution and charge collection in hybrid perovskite materials evolve as chemical complexity increases, highlighting recent results using nondestructive operando synchrotron-based X-ray nanoprobe techniques. The results reveal a strong link between local chemistry and charge collection that must be controlled to develop robust, high-performance hybrid perovskite materials for optoelectronic devices.applications including solar cells, [1,2] lightemitting diodes, [3] lasers, [4] and photodetectors. [5] The exceptional minority carrier diffusion lengths in these materials [6,7] lead to nearly 100% internal quantum efficiency [8] which results in high charge-carrier collection efficiency and high external luminescence efficiency in electron-photon conversion devices. [9] Particularly in the field of photovoltaics (PV), their extraordinary material properties [10][11][12] have enabled perovskite solar absorbers to achieve large improvements in device performance in the past 8 years. The perovskite crystal structure is shown in Figure 1a, where the A-site is CH 3 NH 3 + (MA, methylammonium), the B-site is Pb 2+ , and the X-site is I − following the general perovskite formula ABX 3. After demonstration of a device with 3.8% power conversion efficiency (PCE) by Miyasaka and co-workers in a dye-sensitized solar cell architecture using CH 3 NH 3 PbI 3 , [13] a breakthrough in perovskite photovoltaics occurred in 2012 when the first allsolid-state hybrid perovskite devices were shown by Kim et al., [14] improving the chemical stability of the perovskite and enabling device performance to exceed beyond 9% using CH 3 NH 3 PbI 3 perovskites. With intense investigation of perovskite material properties from research groups all over the world, including bandgap engineering by halide mixing [15,16] and device optimization using A-site mixing, [9,17] the record PCE of hybrid perovskite solar cells reached 22.7% in 2017 after achieving 22.1% PCE in 2015 [18] using a mixture of formamidinium lead iodide (CH(NH 2 ) 2 PbI 3 ) with 5% loading of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) chemistry. [19,20] Surpassing 22% PCE by leveraging the chemical flexibility of the perovskite structure brought hybrid perovskite solar cells on par in efficiency with most polycrystalline solar absor...

Control of detrimental metal impurities is crucial to silicon solar cell performance. Traditional silicon solar cell emitters are diffused in an infinite-source regime and are known to cause strong point defect segregation towards the emitter and thus enhance bulk minority carrier diffusion length. With the advent of ion-implantation and chemical vapor deposition (CVD) glasses, finite-source diffused emitters are attracting interest. This contribution aims to increase their adoption by elucidating the dominant gettering mechanisms present in finite-source diffused emitters. Our findings indicate that infinite-source diffusion is critical for effective segregation gettering, but that high enough surface phosphorus concentration can activate segregation gettering via finite-source diffusion as well. In the case of ionimplanted emitters, the traditional segregation gettering may be considerably enhanced by impurity precipitation in the implanted layer.

We investigate semiconductor p–n junction formation by liquid-phase epitaxy (LPE) using metallic pastes incorporating traditional and nontraditional dopants. The LPE technique enables us to control the shape of doping profiles with a low thermal budget through the choice of solvent, total amount of solvent deposited, and process temperature. We focus here on the Al–B, Zn–P, and Sn–Ga chemistries to dope silicon regions using the chemicophysical properties of a low-eutectic-temperature metallic solvent acting as a matrix for the dissolution of a high concentration of a dopant. Additionally, we developed a capping method enabling doping across a large surface area wafer with a tunable thickness well below 1 μm without film dewetting. In good agreement with thermodynamic simulation of the LPE process, we demonstrate B- and Al-doped regions with a sheet resistance ranging from less than 10 to 300 Ω/sq between 650 and 800 °C, which is significantly lower than the typical temperatures of gas-phase doping processes. Comprehensive electrical simulations suggest that LPE p–n junctions with a low carrier recombination activity can be fabricated via the reduction of surface doping concentration and improved surface recombination velocity. Our investigation of exotic LPE chemistries suggests that emitter saturation currents below 50 fA/cm2 could be achieved at doping concentrations relevant to solar cells.

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