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The fabrication of a low reabsorption emission loss, high efficient luminescent solar concentrator (LSC) is demonstrated by embedding near infrared (NIR) core/shell quantum dots (QDs) in a polymer matrix. An engineered Stokes shift in NIR core/shell PbS/CdS QDs is achieved via a cation exchange approach by varying the core size and shell thickness through the refined reaction parameters such as reaction time, temperature, precursor molar ratio, etc. The as‐synthesized core/shell QDs with high quantum yield (QY) and excellent chemical/photostability exhibit a large Stokes shift with respect to the bare PbS QDs due to the strong core‐to‐shell electrons leakage. The large‐area planar LSC based on core/shell QDs exhibits the highest value (6.1% with a geometric factor of 10) for optical efficiency compared to the bare NIR QD‐based LSCs and other reported NIR QD‐based LSCs. The suppression of emission loss and the broad absorption of PbS/CdS QDs offer a promising pathway to integrate LSCs and photovoltaic devices with good spectral matching, indicating that the proposed core/shell QDs are strong candidates for fabricating high efficiency semi‐transparent large‐area LSCs.

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In recent years, hybrid organic-inorganic halide perovskites have been widely studied for the low-cost fabrication of a wide range of optoelectronic devices, including impressive perovskite-based solar cells. Amongst the key factors influencing the performance of these devices, recent efforts have focused on tailoring the granularity and microstructure of the perovskite films. Albeit, a cost-effective technique allowing to carefully control their microstructure in ambient environmental conditions has not been realized. We report on a solvent-antisolvent ambient processed CH3NH3PbI3−xClx based thin films using a simple and robust solvent engineering technique to achieve large grains (>5 µm) having excellent crystalline quality and surface coverage with very low pinhole density. Using optimized treatment (75% chlorobenzene and 25% ethanol), we achieve highly-compact perovskite films with 99.97% surface coverage to produce solar cells with power conversion efficiencies (PCEs) up-to 14.0%. In these planar solar cells, we find that the density and size of the pinholes are the dominant factors that affect their overall performances. This work provides a promising solvent treatment technique in ambient conditions and paves the way for further optimization of large area thin films and high performance perovskite solar cells.

Colloidal quantum dots (QDs) are widely studied due to their promising optoelectronic properties. This study explores the application of specially designed and synthesized “giant” core/shell CdSe/(CdS)x QDs with variable CdS shell thickness, while keeping the core size at 1.65 nm, as a highly efficient and stable light harvester for QD sensitized solar cells (QDSCs). The comparative study demonstrates that the photovoltaic performance of QDSCs can be significantly enhanced by optimizing the CdS shell thickness. The highest photoconversion efficiency (PCE) of 3.01% is obtained at optimum CdS shell thickness ≈1.96 nm. To further improve the PCE and fully highlight the effect of core/shell QDs interface engineering, a CdSexS1−x interfacial alloyed layer is introduced between CdSe core and CdS shell. The resulting alloyed CdSe/(CdSexS1−x)5/(CdS)1 core/shell QD‐based QDSCs yield a maximum PCE of 6.86%, thanks to favorable stepwise electronic band alignment and improved electron transfer rate with the incorporation of CdSexS1−x interfacial layer with respect to CdSe/(CdS)6 core/shell. In addition, QDSCs based on “giant” core/CdS‐shell or alloyed core/shell QDs exhibit excellent long‐term stability with respect to bare CdSe‐based QDSCs. The giant core/shell QDs interface engineering methodology offers a new path to improve PCE and the long‐term stability of liquid junction QDSCs.

Luminescent solar concentrators (LSCs) can potentially reduce the cost of solar cells by decreasing the photoactive area of the device and boosting the photoconversion efficiency (PCE). This study demonstrates the application of "giant" CdSe/Cd Pb S core/shell quantum dots (QDs) as light harvesters in high performance LSCs with over 1.15% PCE. Pb addition is critical to maximize PCE. First, this study synthesizes "giant" CdSe/Cd Pb S QDs with high quantum yield (40%), narrow size distribution (<10%), and stable photoluminescence in a wide temperature range (100-300 K). Subsequently these thick alloyed-shell QDs are embedded in a polymer matrix, resulting in a highly transparent composite with absorption spectrum covering the range 300-600 nm, and are applied as active material for prototype LSCs. The latter exhibits a 15% enhancement in efficiency with respect to 1% PCE of the pure-CdS-shelled QDs. This study attributes this increase to the contribution of Pb doping. The results demonstrate a straightforward approach to enhance light absorption in "giant" QDs by metal doping, indicating a promising route to broaden the absorption spectrum and increase the efficiency of LSCs.