µ‐Graphene Crosslinked CsPbI3 Quantum Dots for High Efficiency Solar Cells with Much Improved Stability

All‐inorganic perovskite CsPbI3 quantum dots (QDs) offer much better stability for photovoltaic applications. Unfortunately, their cell efficiencies are hindered by the low carrier transport efficiency of QD‐assembled films. In addition, agglomeration‐induced phase change of QDs poses another problem for material and device degradation. Herein, the use of µ‐graphene (µGR) to crosslink QDs to form µGR/CsPbI3 film is demonstrated. It is found that the resultant QDs film provides not only an effective channel for carrier transport, as witnessed by much improved conductivity but also significantly better stability against moisture, humidity, and high temperature stresses. The µGR/CsPbI3 based solar cell shows increased device performance. More specifically, compared to the solar cell without the µGR treatment, VOC is improved to 1.18 from 1.16 V, JSC to 13.59 from 13.17 mA cm−2, and FF to 72.6 from 68.1%, and overall power conversion efficiency to as high as 11.40 from 10.41%, a 12% increase. In addition, the instability originating from the thermal/moisture‐induced QD agglomeration is also greatly suppressed by the µGR crosslinking. The optimized device retains >98% of its initial efficiency after being stored in N2 atmosphere for one month. Importantly, under 60% humidity and 100 °C thermal stresses, the µGR/CsPbI3 devices show much better stability.