Enhanced Performance of Planar Perovskite Solar Cells Using Low-Temperature Solution-Processed Al-Doped SnO2 as Electron Transport Layers.

Lead halide perovskite solar cells (PSCs) appear to be the ideal future candidate for photovoltaic applications owing to the rapid development in recent years. The electron transport layers (ETLs) prepared by low-temperature process are essential for widespread implementation and large-scale commercialization of PSCs. Here, we report an effective approach for producing planar PSCs with Al3+ doped SnO2 ETLs prepared by using a low-temperature solution-processed method. The Al dopant in SnO2 enhanced the charge transport behavior of planar PSCs and increased the current density of the devices, compared with the undoped SnO2 ETLs. Moreover, the enhanced electrical property also improved the fill factors (FF) and power conversion efficiency (PCE) of the solar cells. This study has indicated that the low-temperature solution-processed Al-SnO2 is a promising ETL for commercialization of planar PSCs.

Electronic Properties of a New All-Inorganic Perovskite TlPbI3 Simulated by the First Principles.

All-inorganic perovskites have been recognized as promising photovoltaic materials. We simulated the perovskite material of TlPbI3 using ab initio electronic structure calculations. The band gap of 1.33 eV is extremely close to the theoretical optimum value. Compared TlPbI3 with CsPbI3, the total energy (-3980 eV) of the former is much lower than the latter. The partial density of states (PDOS) of TlPbI3 shows that a strong bond exists between Tl and I, resulting in the lower total energy and more stable existence than CsPbI3.

Solvent annealing of PbI2 for the high-quality crystallization of perovskite films for solar cells with efficiencies exceeding 18.

While most work carried out to date has focused on the solvent annealing of perovskite, in the present work, we focused on the solvent annealing of lead iodide. Based on the two-step spin-coating method, we designed a screening method to search for an effective solvent annealing process for PbI2. PbI2 films were annealed in diverse solvent atmospheres, including DMF, DMSO, acetone, and isopropanol (IPA). We found that the solvent annealing of PbI2 in the DMF, acetone, and IPA atmospheres resulted in dense PbI2 films, which impeded the complete conversion of PbI2 to CH3NH3PbI3. Surprisingly, employing the DMSO solvent annealing process for PbI2 led to porous PbI2, which facilitated the complete conversion of PbI2 to perovskite with larger grain sizes. Solar cells fabricated using the DMSO solvent annealing process exhibited the best efficiency of 18.5%, with a fill factor of 76.5%. This unique solvent annealing method presents a new way of controlling the perovskite film quality for highly efficient solar cells.