Enhanced Interstitial Oxygen-Enabled Efficient CuAl(M)O2 Hole Extractors for Air-Stable All-Inorganic Perovskite Solar Cells

The incorporation of an inorganic hole transport material (HTM) with high hole mobility and matched energetics at the back interface of perovskite/carbon plays a major role in improving the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Here, M3+ (M = Sc, Y, and La)-doped CuAlO2, CuAl(M)O2, with superior p-type conductivity and suitable energy band is inserted between the CsPbBr3 perovskite layer and carbon electrode as an efficient HTM to enhance hole extraction and reduce energy loss within carbon-based CsPbBr3 PSCs. The balance between the increased interstitial oxygen concentration and the carrier scattering caused by the lattice distortion of CuAl(M)O2 endows a higher hole mobility of CuAl(Sc)O2, giving a substantially increased PCE of 10.13% of the CuAl(Sc)O2 tailored CsPbBr3 PSCs, compared with the 6.5% efficiency of the device without HTMs. Moreover, the CuAl(Sc)O2-based CsPbBr3 PSCs without packaging still have 90% of the original efficiency after being stored for 720 h in an air environment with a relative humidity of 85% at 85 °C, exhibiting an outstanding long-term humidity-thermal tolerance.