Organic-inorganic perovskite solar cell are meeting efficiencies of up to 21% now and position themselves as a highly promising next-generation photovoltaic technology. However, until now, the record efficient perovskite device still relies on either expensive organic hole transport materials and or high-temperature sintered TiO2 electron transport layers.[1] This not only bring the challenges to scale-up this technology towards roll-to-roll, but also hampers its important application as a semi-transparent cell into a “tandem junction” device by combining many other currently commercialized PVs technologies (Si and CIGS), in which the "top cell" should integrate the high Voc, less hysteresis, and fully low-temperature deposition merits.    

Here, we demonstrate that a low-temperature processed interface material has the potential to form an almost loss free hole selective interface for planar hetero-junction perovskite based solar cells. By applying it as hole-transporting layer and reducing further interface related losses, a planar configuration device employing CH3NH3PbI3 (band gap of ~1.6 eV) results in a maximum PCE of 17.5% with a highest reported Voc of 1111 mV for an inverted structure (p-i-n) CH3NH3PbI3 based solar cell and effectively avoids hysteresis effect.[2] Impressively, the Voc value can be further boosted to 1530 mV in a large band gap CH3NH3PbBr3 (band gap of ~2.3 eV) based device.[3] To the best of our knowledge, this is the highest reported Voc value for a single junction perovskite solar cell. These results successfully illustrate that this interface material is not only able to fully processed at low temperature condition (oC), but also universally enhance the Voc of the devices employing the different band gap perovskite semiconductors. Finally, by combining FTPS and EL studies we observe a impressive non-radiative Voc loss of CH3NH3PbI3 based perovskite solar cells as low as 0.226 V, a value which is close to the 0.19 V reported for crystalline silicon solar cells and 0.21 V reported for CIGS based solar cells.  

[1]  Hou, Y. et al. "Low-Temperature and Hysteresis Free Electron Transporting Layers for Efficient, Regular and Planar Structure Perovskite Solar Cells." Advanced Energy Materials, DOI: 10.1002/aenm.201501056;

[2]  Hou, Y. et al. "Overcoming the Interface Losses in Planar Heterojunction Perovskite based Solar Cells." Advanced Materials. Under review.

[3]  Chen, S; Hou, Y. et al. "Exploring the limiting open-circuit voltage and the voltage loss mechanism in planar CH3NH3PbBr3perovskite solar cells." Advanced Energy Materials, Under review.