Abstract
Further minimizing the defect state density in the semiconducting absorber is vital to boost the power conversion efficiency of solar cells approaching Shockley-Queisser limit. However, it lacks a general strategy to control the precursor chemistry for defects density reduction in the family of iodine based perovskite. Here the alkaline environment in precursor solution is carefully investigated as an effective parameter to suppress the incident iodine and affects the crystallization kinetics during film fabrication, via rationale adjustment of the alkalinity of additives. Especially, a ‘residual free’ weak alkaline is proposed not only to shrink the bandgap of the absorber by modulating the stoichiometry of organic cation, but also to improve the open circuit voltage in the resultant device. Consequently, the certified efficiency of 20.87% (Newport) is achieved with one of the smallest voltage deficits of 413 mV in the planar heterojunction perovskite solar cell.
Highlights
Further minimizing the defect state density in the semiconducting absorber is vital to boost the power conversion efficiency of solar cells approaching Shockley-Queisser limit
The corresponding mixed perovskite solar cells achieve an average power conversion efficiency (PCE) of 20.87%. This modified absorber possesses a smaller bandgap, but the resultant device revealed unambiguous improvement in the open-circuit voltage (VOC), corresponding to a VOC deficit of 413 mV, which is one of the smallest certified value in the planar perovskite solar cells. These findings provide a universal approach for defect reduction in iodide-based perovskite films, which substantially reduce the energy and voltage loss to boost the efficiency of the devices
Formamidine iodide (FAI) and methylammonium iodide (MAI) can be oxidized to form I2 and/or other by-products, which induces the nonstoichiometric ratio in the precursor solution
Summary
Further minimizing the defect state density in the semiconducting absorber is vital to boost the power conversion efficiency of solar cells approaching Shockley-Queisser limit. 1234567890():,; Organic–inorganic hybrid perovskite materials have attracted broad attention[1], owing to their low fabrication cost and intriguing optical and electronic properties[2,3,4,5] It witnessed the power conversion efficiency (PCE) of perovskite solar cells boosted from 3.8%6 to a certified 23.7% rapidly[7,8,9,10]. To enable a truly competitive PCE of perovskite solar cells as that of the most efficient inorganic counterpart, e.g., GaAs, it is required to further reduce their energy loss This relies on the improved charge generation and mitigated non-radiative charge recombination within the complete device. It lacks a feasible approach to be universally adopted in various halide perovskites, which suppresses the incidental I2 in the absorber for enhanced device performance with reduced energy and voltage loss
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