The unprecedented rapid ascending efficiency of perovskite-structured CH3NH3PbX3 solid-state solar cells have raised a storm of research effort. Despite the success in boosting efficiency, perovskite solar cells are still facing several critical challenges, including the instability of the key material CH3NH3PbX3, especially in moisture, the use of environment-hazardous lead, the costly and unstable complex organics as hole transport materials, the use of precious metals as back cathode, the hysteresis in current-voltage scans, the tricky engineering of good-quality perovskite films, and the basic science understanding of the unusual excellence in both charge transport and light harvesting of CH3NH3PbX3, etc. To tackle these critical challenges, we recent demonstrated that nickel, as an industrial commodity metal with work function of 5.1 eV, can replace gold as the back cathode in perovskite solar cells with competitive performance to gold-cathoded cells. We show that the work function and the conductivity of the cathode are both fundamentally important factors impacting the photovoltage and fill factor of the perovskite solar cells. Furthermore, we show that when partial iodides in CH3NH3PbI3 are replaced with pseudohalide ions thiocyanate (SCN-), the resulting SCN-containing perovskite films strikingly rival the conventional CH3NH3PbI3 films in terms of moisture-tolerance as evidenced by their tolerance in 95% relative humidity in air for over 4 hours without significant degradation, in contrast to CH3NH3PbI3 films that degraded in less than 1.5 hours. The solar cells based on the SCN-containing perovskite thin films exhibit efficiency comparable to that of CH3NH3PbI3-based cells fabricated in the same way. In this talk, I will also present our recent study on the optical and electronic properties of perovskite materials under extreme chemical and physical conditions.

Challenges and opportunities for perovskite solar cells

251st National Meeting (2016)

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