Solution-processed organometallic halide perovskites have obtained rapid development for light-emitting diodes (LEDs) and solar cells (SCs). These devices are fabricated with similar materials and architectures, leading to the emergence of perovskite-based light-emitting solar cells (LESCs). The high quality perovskite layer with reduced nonradiative recombination is crucial for achieving a high performance device, even though the carrier behaviors are fundamentally different in both functions. Here CHNHPbBr quantum dots (QDs) are first introduced into the antisolvent in solution phase, serving as nucleation centers and inducing the growth of CHNHPbI films. The heterogeneous nucleation based on high lattice matching and a low free-energy barrier significantly improves the crystallinity of CHNHPbI films with decreased grain sizes, resulting in longer carrier lifetime and lower trap-state density in the films. Therefore, the LESCs based on the CHNHPbI films with reduced recombination exhibit improved electroluminescence and external quantum efficiency. The current efficiency is enhanced by 1 order of magnitude as LEDs, and meanwhile the power conversion efficiency increases from 14.49% to 17.10% as SCs, compared to the reference device without QDs. Our study provides a feasible method to grow high quality perovskite films for high performance optoelectronic devices.
Metal-catalyzed chemical vapor deposition (CVD) growth of graphene is one of the most important techniques to produce high quality and large area graphene films.
Fullerene (C 60 ) has been demonstrated, using vapor deposition, to be a good electron transport layer (ETL) and different thicknesses have been utilized in n-i-p configuration perovskite solar cells. However, an underlying reason for the variation in thicknesses, which hinders the reproducibility of perovskite solar cells employing a C 60 ETL, has not been well-examined. This study reveals that the surface roughness of the conducting glass, such as fluorine doped tin oxide (FTO), affects the photovoltaic performance while optimizing the thickness of the vacuum deposited compact C 60 ETL. A low-thickness C 60 ETL retains a surface roughness and Ohmic behavior similar to bare FTO due to physical defects at the C 60 /FTO interface. Increasing the thickness further reduces the defects at the C 60 /FTO interface and facilitates an enhanced electron extraction from a vacuum co-deposited methyl-ammonium lead iodide perovskite light absorber. As a result, a perovskite solar cell with a homogenously covered C 60 ETL on an FTO substrate delivers a power conversion efficiency of 14.63%. These comprehensive characterizations support the finding that suppression of defects at the C 60 / FTO interface results in an improved photovoltaic performance. This work demonstrates that the surface roughness of FTO needs to be considered for a decisive compact ETL for enhanced photovoltaic performance and reproducibility.
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