During the past decade, inorganic CQDs, namely the lead chalcogenides (e.g., PbS), have attracted tremendous attention in solution-processed solar cells. Due to the great efforts on CQDs synthesis modification, [7][8][9] surface passivation, [10][11][12] and device fabrication optimization, [13][14][15][16] PbS QD solar cells continue to progress at an extraordinary rate, improving overall efficiencies by ≈1% per year and currently have a certified power conversion efficiency (PCE) exceeding 12%. [17] Meanwhile, the past decade has witnessed unprecedented success of organicinorganic hybrid perovskites in PV applications, with the reported PCE of perovskite solar cells exceeding 23%. [18][19][20][21][22][23][24][25][26][27][28] However, the challenging stability issues of these hybrid perovskites further motivate the research of all-inorganic perovskites (CsPbX 3 , X = Cl − , Br − , I − or mixed halides) without any volatile organic components. [29][30][31][32][33][34][35][36][37][38] Among these all-inorganic perovskite materials, α-CsPbI 3 exhibits an ideal optical bandgap (E g ) of 1.73 eV for PV applications. However, the nonphotoactive orthorhombic phase (E g = 2.82 eV) is more thermodynamically preferred at low temperature. [29] Therefore, the perovskite phase of CsPbI 3 usually requires complex annealing processes at high temperature to achieve satisfactory film quality. As mentioned above, QD technology offers colloidal synthesis of conventional bulk materials, which Surface manipulation of quantum dots (QDs) has been extensively reported to be crucial to their performance when applied into optoelectronic devices, especially for photovoltaic devices. In this work, an efficient surface passivation method for emerging CsPbI 3 perovskite QDs using a variety of inorganic cesium salts (cesium acetate (CsAc), cesium idodide (CsI), cesium carbonate (Cs 2 CO 3 ), and cesium nitrate (CsNO 3 )) is reported. The Cs-salts post-treatment can not only fill the vacancy at the CsPbI 3 perovskite surface but also improve electron coupling between CsPbI 3 QDs. As a result, the free carrier lifetime, diffusion length, and mobility of QD film are simultaneously improved, which are beneficial for fabricating high-quality conductive QD films for efficient solar cell devices. After optimizing the post-treatment process, the short-circuit current density and fill factor are significantly enhanced, delivering an impressive efficiency of 14.10% for CsPbI 3 QD solar cells. In addition, the Cs-salt-treated CsPbI 3 QD devices exhibit improved stability against moisture due to the improved surface environment of these QDs. These findings will provide insight into the design of high-performance and low-trap-states perovskite QD films with desirable optoelectronic properties. Perovskite Quantum DotsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.Solution-processed colloidal quantum dots (CQDs) are promising candidates for the next generation photovoltaics (PVs) due to the excellent tuna...

Emerging all-inorganic perovskite nanocrystals can retain a desired crystal structure under ambient conditions and offer easy solution processability. In this work, we have demonstrated CsPbI 3 perovskite quantum dot (QD) solar cells with a remarkable efficiency approaching 13% and an extremely low energy loss of 0.45 eV by employing a series of dopant-free polymeric hole-transporting materials (HTMs). The CsPbI 3 QD solar cells use polymer HTMs to achieve efficient charge extraction at QD/polymer interfaces and avoid device instability caused by complex doping and oxidation processes required by conventional Spiro-OMeTAD. Meanwhile, the CsPbI 3 QD photovoltaic devices can be fabricated at room temperature and exhibit more reproducible film quality, showing potential advantages over current all-inorganic thin-film perovskite solar cells. We believe that our findings will catalyze the development of new device structures, specifically for perovskite QDs, and help realize the promising potential of all-inorganic perovskite solar cells.

A ligand-assisted matrix to regulate surface and packing states of perovskite quantum dots (QDs) is demonstrated, which involves a ligand exchange and a mild thermal annealing process that are triggered by guanidinium thiocyanate. Consequently, the CsPbI 3 QD solar cells (QDSCs) deliver a champion power conversion efficiency of 15.21%, which is the highest report among all CsPbI 3 QDSCs.

Colloidal perovskite nanocrystals, or quantum dots (QDs), have quickly emerged and exhibited unique opportunities for optoelectronic applications.

As effective light absorbers in solar cells, CsPbI3 all-inorganic perovskite quantum dots (QDs) have received increasing attention, benefitting from their suitable optical band gap and thermal stability. However, the easy cubic to yellow orthorhombic phase transition hinders their further application in stable photovoltaic devices. CsPbBr3 QDs have been targeted as a promising material for ultrahigh voltage and stable solar cells. In this work, we first develop a simple yet efficient post-treatment method using guanidinium thiocyanate (GASCN), which is able to exchange the native capping ligands of CsPbBr3 QDs, thus improving the carrier transport properties through enhanced electrical coupling between QDs. Additionally, the morphology and crystalline properties of solid QD films are also improved. Therefore, simultaneously improved open-circuit voltage (V oc), short-circuit current density (J sc), and fill factor (FF) were obtained in the corresponding CsPbBr3 QD devices. Finally, the QD solar cells based on optimal hole-transporting layers delivered the highest efficiency exceeding 5% together with an ultrahigh V oc of 1.65 V, representing the most efficient CsPbBr3 QD solar cells to date. More importantly, the CsPbBr3 perovskite QD solar cells developed here exhibit excellent stability, ultrahigh voltage, and high transparency over the entire visible spectrum region, demonstrating their great potential in applications like solar windows of greenhouse and hydrogen generation driven by perovskite solar cells.