Reduced Recombination Losses in Evaporated Perovskite Solar Cells by Postfabrication Treatment

摘要

The photovoltaic perovskite research community has now developed a large setof tools and techniques to improve the power conversion efficiency (PCE). Onesuch arcane trick is to allow the finished devices to dwell in time, and the PCEoften improves. Herein, a mild postannealing procedure is implemented oncoevaporated perovskite solar cells confirming a substantial PCE improvement,mainly attributed to an increased open-circuit voltage (V_∝). From a VOC ofaround 1.11 V directly after preparation, the voltage improves to more than 1.18 Vby temporal and thermal annealing. To clarify the origin of this annealing effect,an in-depth device experimental and simulation characterization is conducted. Asimultaneous reduction of the dark saturation current, the ideality factor (nid),and the leakage current is revealed, signifying a substantial impact of thepostannealing procedure on recombination losses. To investigate the carrierdynamics in more detail, a set of transient optoelectrical methods is first evaluated,ascertaining that the bulk carrier lifetime is increased with deviceannealing. Second, a drift-diffusion simulation is used, confirming that thebeneficial effect of the annealing has its origin in effective bulk trap passivationthat accordingly leads to a reduction of Shockley–Read–Hall recombination rates.