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A high open-circuit voltage inverted perovskite solar cell based on a CH3NH3PbBr3 absorber and ICBA acceptor is reported. The CH3NH3PbBr3 film fabricated under ambient atmosphere at a moderate temperature (∼100 °C) using a two-step spin-coating method is composed of aggregated nano-grains. Upon solvent annealing of the CH3NH3PbBr3/ICBA film, the efficiency of the resulting cell increases from 1.71% to 7.50% with a remarkably high open circuit voltage (Voc) of ca. 1.60 V. ICBA acts not only as a high LUMO acceptor to realize high Voc but also as a mending agent to increase the efficiency of the cell by penetrating into the defects/voids of the CH3NH3PbBr3 film via solvent annealing as evidenced by TRPL, XPS and SEM data. Solvent annealing of the active layer was proved to be simple and effective device engineering to improve the efficiency of the perovskite cell based on a low quality film and the Voc of the inverted perovskite cell can be tuned by the LUMO level of the acceptor were revealed. The CH3NH3PbBr3/ICBA film is semi-transparent with an average 50% transmittance under visible light. The moderatetemperature processed CH3NH3PbBr3 solar cell with high Voc and a semi-transparent absorber has great potential for application as the top cell in a tandem solar cell.
Wu et al. (Fri,) studied this question.