Hole Transport Layer For CsPbI₂Br Perovskite Solar Cells

In recent years,all-inorganic perovskite solar cells(PeSCs)have developed rapidly because they have better light and thermal stability and balanced carrier mobility than organic-inorganic hybrid PeSCs.To date,the hightest PCE of all inorganic PeSCs with n-i-p and p-i-n structures have reached 19.02%and 15.19%.The hole transport layer(HTL)in p-i-n type PeSCs not only contributes to the hole transport but also serves as the underlayer for perovskite growth or deposition.Therefore,optimization of HTL is very important to improve device performance.First of all,we report a dopant-free mixture(SpiPA)of Spiro-OMeTAD and PTAA,which exhibits tunable surface wettability due to the lateral phase separation in the mixed thin film.One of mixtures SpiPA-? was employed as HTL for inverted CsPbI2Br-PeSCs,yielding an enhanced efficiency of 12.52%with significantly reduced hysteresis compared to the devices with pristine Spiro-OMeTAD(10.26%),PTAA(9.05%)and conventional NiOx(10.75%).It was found that SpiPA-? with suitable wettability facilitates the growth of large CsPbI2Br crystal grains with reduced defect density.Thus,device performance has been improved significantly.In addition,we synthesized ligand-free E-NiOx nanoparticles.E-NiOx HTL which can be treated at low temperature was prepared by dispersing the E-NiOx nanocrystals in ethanol.The PCE of inverted CsPbI2Br-PeSCs based on E-NiOx is 10.62%,which is equivalent to that of PeSCs with traditional NiOx.It can be found the CsPbI2Br perovskite on SpiPA-? exhibits a better film with larger grain size compared to traditional devices.The specific mechanism needs more research.