Stable Organic Inorganic Perovskite Solar Cells without Hole Conductor Layer Achieved via Cell Structure Design and Contact Engineering
Within the past few years, the record efficiency of inorganic organic perovskite solar cell (PSC) has improved rapidly up to over 20% However, the viability of commercialization of the PSC technology has been seriously questioned due to the moisture and thermal induced instabilities. Here, it is demonstrated that these issues may be mitigated via cell structure design and contact engineering. By employing the hole conductor layer free cell structure and a bi layer back contact consisting of a carbon/CH3NH3I composite layer and a compact hydrophobic carbon layer, the PSCs have shown excellent stability, inhibiting moisture ingression and heat induced perovskite degradation. It is found that, the unique bi layer contact enables the optimization of perovskite absorbers during thermal stress. As a result, instead of degradation, the devices present enhanced performance under heating at 100 degC for 30 min. The best performing cell shows a final efficiency of 13.6% from an initial efficiency of 11.3% after thermal stress. Upon encapsulation, these cells can even retain 90% of the initial efficiencies after water exposure and over 100% initial efficiency under thermal stress at 150 degC for half an hour. This approach provides a facile way for stabilizing the PSCs and opens a door for viable commercialization of the emerging PSC technology.