2, The University of Texas at Dallas, Richardson, Texas, United States
3, University of Toledo/Bowling Green University, Toledo, Ohio, United States
4, University of Washington, Seattle, Washington, United States
5, Duke University, Durham, North Carolina, United States
An important component of improving the commercial viability of perovskite solar cells is the development of device architectures that are compatible with low-temperature processing methods. In this work, we investigate the performance of solar cells in which the hole transport layer (HTL), composed of delafossite CuCrO2, is deposited at room temperature. The HTL films are prepared by spin-coating suspensions of hydrothermally-synthesized CuCrO2 nanoparticles, whose small size (~10 nm) and nearly spherical shape enable the formation of highly compact films, even for very thin layers. While DFT calculations predict that both rhombohedral and hexagonal polytypes of the delafossite structure may be present due to the similarity in their formation energies, their optoelectronic properties should be essentially identical, and well-suited for the role as HTL in perovskite solar cells. Experimental measurements confirm that the CuCrO2 films are highly transparent and possess favorable valence band alignment relative to the MAPbI3 absorber, as well as p-type conductivity. Solar cells fabricated using a glass/ITO/CuCrO2/MAPbI3/C60/BCP/Ag device architecture perform with low hysteresis and stabilized power conversion efficiency of over 14%. These results pave the way for the development of cost-effective, low-energy-input device architectures based on CuCrO2 HTLs.