Regulating three-layer full carbon electrodes to enhance the cell performance of CsPbI₃ perovskite solar cells

Carbon-based perovskite solar cells exhibit a promising application prospect due to its cost effective and attractive hydrophobic nature and chemical inertness, but are still limited to unsatisfied device efficiency. Herein, we design a triple-layer full-carbon electrode for n-i-p typed perovskite solar cells, which is comprised of a modified macroporous carbon layer, a highly conductive graphite layer and a thin dense carbon layer, and each layer undertakes different contribution to improving the cell performance. Based on this full-carbon electrode, inorganic CsPbI₃ perovskite solar cells exhibit >19% certified efficiency which is the highest result among carbon-based CsPbI₃ devices. On one hand, carbon quantum dots decorated on the macro-porous carbon layer can realize better energy alignment of full-carbon electrode/spiro-OMeTAD/CsPbI₃ interface, on the other hand, highly conductive graphite layer is advantageous to carrier transporting. Typically, the top dense carbon layer exhibits significant thermal radiation ability, which can reduce the operational temperature of devices by about 10 °C, both from theoretical simulation and experimental testing. Thereby, packaged full-carbon electrode based CsPbI₃ cells exhibit much better photothermal stability at ~70°C accompanied by white light emitting diode illumination, which exhibit no efficiency degradation after 2000 h continuous operational tracking.