Qunwei Tang

High‐Purity Inorganic Perovskite Films for Solar Cells with 9.72 % Efficiency

All-inorganic perovskite solar cells with high efficiency and improved stability are promising for commercialization. A multistep solution-processing method was developed to fabricate high-purity inorganic CsPbBr3 perovskite films for use in efficient solar cells. By tuning the number of deposition cycles (n) of a CsBr solution, the phase conversion from CsPb2 Br5 (n ≤3), to CsPbBr3 (n=4), and Cs4 PbBr6 (n≥5) was optimized to achieve vertical- and monolayer-aligned grains. Upon interfacial modification with graphene quantum dots, the all-inorganic perovskite solar cell (without a hole-transporting layer) achieved a power conversion efficiency (PCE) as high as 9.72u2009% under standard solar illumination conditions. Under challenging conditions, such as 90u2009% relative humidity (RH) at 25u2009°C or 80u2009°C at zero humidity, the optimized device retained 87u2009% PCE over 130u2005days or 95u2009% over 40u2005days, compared to the initial efficiency.

Simplified Perovskite Solar Cell with 4.1% Efficiency Employing Inorganic CsPbBr3 as Light Absorber

Perovskite solar cells with cost-effectiveness, high power conversion efficiency, and improved stability are promising solutions to the energy crisis and environmental pollution. However, a wide-bandgap inorganic-semiconductor electron-transporting layer such as TiO2 can harvest ultraviolet light to photodegrade perovskite halides, and the high cost of a state-of-the-art hole-transporting layer is an economic burden for commercialization. Here, the building of a simplified cesium lead bromide (CsPbBr3 ) perovskite solar cell with fluorine-doped tin oxide (FTO)/CsPbBr3 /carbon architecture by a multistep solution-processed deposition technology is demonstrated, achieving an efficiency as high as 4.1% and improved stability upon interfacial modification by graphene quantum dots and CsPbBrI2 quantum dots. This work provides new opportunities of building next-generation solar cells with significantly simplified processes and reduced production costs.

Toward charge extraction in all-inorganic perovskite solar cells by interfacial engineering

All-inorganic perovskite solar cells (PSCs) are a promising solution to address the poor stability of organic–inorganic hybrid PSC devices under humidity and thermal attacks. However, the severe interfacial charge recombination from large energy differences has markedly limited the further enhancement of power conversion efficiency. The charge extraction from perovskite layer has been improved by setting intermediate energy levels using quantum dots (QDs) through interfacial engineering. In the current study, CuInS2/ZnS QDs with tunable bandgaps and hole-transporting behavior were prepared to modify the CsPbBr3/carbon interface. Arising from the improved charge separation, a power conversion efficiency of 8.42% was achieved for QD tailored inorganic PSC in comparison with 6.01% for pristine devices. These all-inorganic PSCs present unprecedented stability under high humidity and significant improvements in the fill factor, short-circuit photocurrent, and open-circuit voltage.

Alloy-Controlled Work Function for Enhanced Charge Extraction in All-Inorganic CsPbBr3 Perovskite Solar Cells

All-inorganic CsPbX3 (X=I, Br) perovskite solar cells are regarded as cost-effective and stable alternatives for next-generation photovoltaics. However, sluggish charge extraction at CsPbX3 /charge-transporting material interfaces, which arises from large interfacial energy differences, have markedly limited the further enhancement of solar cell performance. In this work, the work function (WF) of the back electrode is tuned by doping alloyed PtNi nanowires in carbon ink to promote hole extraction from CsPbBr3 halides, while an intermediate energy by setting carbon quantum dots (CQDs) at TiO2 /CsPbBr3 interface bridges electron transportation. The preliminary results demonstrate that the matching WFs and intermediate energy level markedly reduce charge recombination. A power conversion efficiency of 7.17u2009% is achieved for the WF-tuned all-inorganic perovskite solar cell, in comparison with 6.10u2009% for the pristine device, and this is further increased to 7.86u2009% by simultaneously modifying with CQDs. The high efficiency and improved stability make WF-controlled all-inorganic perovskite solar cells promising to develop advanced photovoltaic platforms.